Causes of hard bolt lift?

[andym79]

Or in the case causes of hard lever operation.

Are there any other causes than high pressure that would cause a lever action rifle to be very hard to open?

Background, I have put a fair number around 100 rounds through this rifle using trailboss and H4227 with no problems what so ever.

I obtaine a load from a third party, published, but not by a major reloading, powder or bullet manufacturer.

I ran the load through quickload and it looked fine, around 18000psi (as far as I know the action and this cartridge has been proofed to 64000psi, so a huge margin for error????

I wanted to reduce the load in order to achieve a desired velocity, reduce recoil and minimise or prevent leading. So I tested some loads at load and -1 through to - 5.5 (5 of each) all seemed to work fine, all hit an 8" target area at 100 yards. There were no signs of pressure, all primers looked normal and no extraction issues!

I took the same rifle back to the range two days later, with 20 of the most promising load loaded. The first two shoots missed the target and were around a foot wide of the same, extraction and primers were normal. The third shot missed by the same margin, I couldn't open the lever at first, I waited 2-3 minutes and then with a hell of a lot of effort it opened. The case looked normal, the primer looked normal. I fed the empty case back into the rifle it slipped in fine and then extracted fine? I then tried it again, same thing, again, on the forth chambering inj went in fine, but took a lot of effort to extract (I assume this was the same orientation as upon firing).

What happened? When I say effort I mean a serious amount (though no tools were required). I can only assume a pressure spike?

The powder in question is fast, double base and extruded (N110)
The cartridge a 375W.
The projectile 379-250 LEE.
Cases winchester 3rd firing.

It may not be the powder to blame as there is one other factor, I slugged my bore at .376" and have been using the bullets unsized at .379" (I have order a .377" die but the post is letting me down on this item). Whilst .003" over bore is a touch too much this doesn't explain the 125ish rounds success before number 126. Was it a pressure spike due to a reduction in the powder or did the bullet stick for a 1/2 ms before moving on?

I have been reloading cast for a while now, but until recently I had always exclusively taken my reloading data from Lyman or Hodgdon (ADI) as I was exclusively using their powders (I am in no way blaming VV powders). I did however step in to uncharted territory and in doing so may have invited unecessary risk!

Is this a phenomenon likely to repeat itsels, am I trying to push too big a bullet with to little powder?

Have I been stupid?

[Ben]

What kind of rifle is this ?

Could be a malfunction of the rifle and not the loads ?

[andym79]

What kind of rifle is this ?

Could be a malfunction of the rifle and not the loads ?
Winchester 94 Big bore 1980, its in good shape.

I did carry out due dillegence to a point. N110 is frequently used in a number of reduced cast loads in europe, in various rifles and in cases from the 22 hornet to the 45/70. I did however take it down some more. I also checked to confirm N110 does not behave like H110 and more similarly to Alliant 2400. Still????

Is a heavy bolt lift the first sign of pressure with flattened primers coming next?

As an extra I pulled and weighed the charge all were what I expected, as they shoul have been, I weighed each charge on the scale, which I compare with a second scale at random. After weighing each charge I then seated a bullet, rather than weighing all the charges. A slower process, but one I have got in to doing for any load that can be double charged!

[Ben]

I think the rifle needs a trip to a reptuable gunsmith that has a good working knowledge of lever action action rifle internals.

The rifle needs to be fully disassembled to determine if any of the parts are damaged, worn, broken.

The chamber of the rifle needs a good cleaning and examination by the gunsmith with proper illumination in the chamber to look for problems there.

He should be able to identify the problem.

Ben

[Cherokee]

Have you measured the offending fired case in comparison to others that worked fine ? Have you examined the action parts to see if there is any binding ?

[andym79]

I think the rifle needs a trip to a reptuable gunsmith that has a good working knowledge of lever action action rifle internals.

The rifle needs to be fully disassembled to determine if any of the parts are damaged, worn, broken.

The chamber of the rifle needs a good cleaning and examination by the gunsmith with proper illumination in the chamber to look for problems there.

He should be able to identify the problem.

Ben

So you think that the problem could well be with the rifle and not the load?

What do you think the problem might be then Ben?

[andym79]

Have you measured the offending fired case in comparison to others that worked fine ? Have you examined the action parts to see if there is any binding ?

No that would be wise, but it was only the 3rd firing and the previous two firings were light. I shall measure the batch of 50 and see if the offending round is longer or had a greater diameter.

It would be good if it was just the brass and not the load or worse the rifle!

[44man]

I will never advocate below minimum book loads for any powder. I don't care what someone says.
If you want better results from a large case, go to slower powders and stop fooling with pistol or shotgun powders. I would be using the 4895 or 3031 range, Varget too.
What in the world prompted you to use N110? It is faster then H110. That is a big bore, not a pellet gun.

[RickinTN]

All the above could be correct....or....this time of year humidity is quite high. Could it be you have a small amount of rust in the chamber? It's been my experience that a bit of rust in the chamber will give symptoms as you describe. Might be worth checking out.
Rick

[Shiloh]

How many trips on the brass??

I just serviced mine. Full length sizing and trimming. Works fine now.
This is a bolt gun however. Not a lever action. My sons lever gun works best with full length sized brass.

Shiloh

[44man]

Been working with my 30-30 Marlin and just size enough for easy chambering, die is up a little off the shell holder. Still need to trim often due to bolt compression.

[44man]

Shooting cast I tried all loads listed here and all failed big time. Sorry, Unique and so many powders were a huge loss. Went to jacketed loads with better powders and get less then 1" at 100 yards.
What is it about cast that makes guys use the wrong powders?

[aspangler]

I know this may sound like a stupid question but, did you clean the sizing lube off the cases before you loaded them. And especially before putting them in the rifle? A little lube can cause the problem you describe. It causes the casing to stick to the chamber wall. Just my .02.

[44man]

Instant max pressure against a bolt instead of extending pressure down the bore. Primer pressure pushing a boolit out before ignition, many things to look at. Dump the powder, it does not fit.

[Larry Gibson]

Picture of the stuck case?

Are you FL sizing the cases, partial sizing or what?

Are there any burnished or scrape marks on the stuck case up towards the case mouth?

What is the load used?

Did you use a filler of wad?

Do cases now stick with normal loads?

And andy, after numerous posts on numerous threads and on numerous forums you've made I have to agree with 44man; "What is it about cast that makes guys use the wrong powders? " especially if you've not that much reloading/experimenting experience?

Larry Gibson

[sthwestvictoria]

I wanted to reduce the load in order to achieve a desired velocity, reduce recoil and minimise or prevent leading. So I tested some loads at load and -1 through to - 5.5 (5 of each) all seemed to work fine, all hit an 8" target area at 100 yards. There were no signs of pressure, all primers looked normal and no extraction issues!



Are you referring to these loads in the Lever section (http://castboolits.gunloads.com/showthread.php?249088-Vihtavuori-N110-in-30-30-or-375W-38-55):

Tried some VV N110 in the 375 Winchester today behind the Lee 379-250 BB. It seemed to like it. These shoots were taken sitting, peep sights at 100 yards. Range 62F blue sky 2-5mph wind left to right.
http://i60.tinypic.com/anlte9.jpg
Green = 12.5 grains
Purple = 14 grains
Pink = 15.5 grains
Red= 17 grains
The 14 grains at 1230fps looks like my new load in the 375W, accurate and with a soft fast push. Will try and test the same powder a bit lower in the 30-30 soon.

Then:


I took the same rifle back to the range two days later, with 20 of the most promising load loaded. The first two shoots missed the target and were around a foot wide of the same, extraction and primers were normal. The third shot missed by the same margin, I couldn't open the lever at first, I waited 2-3 minutes and then with a hell of a lot of effort it opened.


Which seems confusing. If you state that you loaded 20 of the most accurate loads (14grains N110) which on the first testing date you got that lovely purple group, why was the second loading (when bullets sprayed and even missed the target and then the bolt stuck) so different?
The wild variation in accuracy from that first group to the second seems to suggest there was some core difference in the load between the two days. Did you test velocity the second time you shot the load ?

[Harter66]

I knew a guy that had a 30-30 of similar vintage same model. At different times he had shot probably every brand of ammo in that and a 20s vintage 94' .He stuck a case bad enough to need a smith to get it out 3 times in the newer rifle ,mean while the older rifle just ''chewed em'up and spit em' out'' . In that case it was a particular brands brass that just would not talk to that rifle. The solution was to simply not shoot PMC in that rifle. My Dad had a 22-250 that would swell up Win brass even w/low end loads but shot Rem and even reformed GI brass fine. I have a custom wildcat that I ''made a little mistake with'',God bless early/pre-war GI actions, that had a 260 hole where the primer cup used to be w/o any hard lift.
My situations may be unique ,because if it is bizarrely unlikely it happens to me,but hard lift isn't always a product of excessive pressure, and over pressure doesn't always beget hard lift.
1 last example, a start load of Blue Dot once stuck cases in a 357 revolver using the exact same componets as the Speer book. They weren't a little sticky they were drive them out w/a 4oz ballpeen and a brass punch stuck. Just 1 gun but a prime example of a particular componet not working w/a particular gun.

[country gent]

Lever actions arnt known for alot of camming force in or out. Is the action mechanisim properly lubed and cleaned in good working order? To long cases or thick necks can also give high pressure sighns with starting loads and below. A simple chamber cast to get neck dia in chamber and a measurement of loaded rounds could be enlightening. Also finding max case length and comparing to tour brass may shed some light on this. How does the action feel when cycling it empty? Not the best test as there is little load force there to give comparison to. May just be a dry dirty mechanisim sticking. But would also check loads and cases in comparison.

[243winxb]

Leading.

[MBTcustom]

I wish you were close enough to come by the shop. We could scope that rifle and do a chamber cast.
Without seeing it, I hesitate to give an opinion, but the thought that is running through the back of my mind is perhaps a rung chamber (let's hope not).
I agree with the advice here. Either go see your smith, or buy a borescope and some cerosafe.
Sorry this is happening to you.
The one thing I would like to suggest (rather adamantly but with respect) is that you fire this gun no more till you have a very clear explanation of the trouble by a professional.
When things are not going right, its the rifles way of warning you that something may be seriously wrong, and should never be ignored.

[fouronesix]

Agree with all who have posted possibilities- could be any number of things. The primer flattening indicator is not the best when assessing this issue- hard extraction especially with a lever gun. Bolt guns will also do this once the brass has been fired a few times and the base of the body starts to work harden and not shrink back as much as with newer brass. The work hardening issue with the lever is seen even earlier in the number of reloading cycles because of the lack of camming power inherent in the lever action.

If the load, pressure, chamber and mechanics of the action are OK then a better sizing of the body or even a small base die will help… but the fact still remains the brass is getting stretched (especially in a lever gun) and work hardened, so maybe time to start with new brass.

Also the load (pressure) may be suspect, as has been suggested- but obviously unknown.

Without the thing in hand and more very detailed info, who really knows? At this point a visit to a knowledgeable gunsmith is probably warranted.

[andym79]

Gunsmiths are like gold here down under, I know of only one here in Adelaide.
The brass was only on its 3rd firing, but I was not FL sizing.
I used no wads or fillers as it seemed pointless with a fast powder.

I cleaned the rifle up, it wasn't that dirty. The action cycles fine empty, and cycled fine with many empty fired cartridges. I will measure all cases and check to see if the offender is different.

I will certainly cease using this rifle with N110 and will not consider firing it till I have a 377 sizing die. I will FL the cases and clean up all the necks. I will clean it again, and find a way to get a good look at the chamber.

[Driver man]

I cant help but wonder if your cases need trimming to correct length.

[fouronesix]

Gunsmiths are like gold here down under, I know of only one here in Adelaide.
The brass was only on its 3rd firing, but I was not FL sizing.
I used no wads or fillers as it seemed pointless with a fast powder.

I cleaned the rifle up, it wasn't that dirty. The action cycles fine empty, and cycled fine with many empty fired cartridges. I will measure all cases and check to see if the offender is different.

I will certainly cease using this rifle with N110 and will not consider firing it till I have a 377 sizing die. I will FL the cases and clean up all the necks. I will clean it again, and find a way to get a good look at the chamber.

Sounds like a good plan. Checking case length is a good idea. Over-length cases won't cause hard extraction but can surely cause higher pressure that can cause hard extraction. Using an FL sizer is usually a must for lever guns because of this very problem. Partial FL or neck sizing will work only so long, for just so many resizings…. then these type difficult extraction problems usually start popping up with lever guns. good luck!

[andym79]

Are you referring to these loads in the Lever section (http://castboolits.gunloads.com/showthread.php?249088-Vihtavuori-N110-in-30-30-or-375W-38-55):


Then:


Which seems confusing. If you state that you loaded 20 of the most accurate loads (14grains N110) which on the first testing date you got that lovely purple group, why was the second loading (when bullets sprayed and even missed the target and then the bolt stuck) so different?
The wild variation in accuracy from that first group to the second seems to suggest there was some core difference in the load between the two days. Did you test velocity the second time you shot the load ?

I wish I knew why the second loading was so different! Powder was the same, charge was the same, lube the same, same alloy, same projectile, same brass cases, same primers. Even the weather conditions including temperature were the almost the same.

I hope it was just a bad case or a build up of lead and lube. As I said no more N110 or 379" projectiles for this rifle. 376-377" and my trusty H4227 or H4198 from now on.

That still doesn't ditract from my desire to try to understand why this happened. Hopefully further analysis of the brass and chamber will shed some light on it.

No I didn't check velocity the second time around as the ES was low between rounds the first time! Wish that I had now. The only thing I can say and I cant really described it adequatley but the recoil and noise felt/seemed different from two days earlier!

[andym79]

I knew a guy that had a 30-30 of similar vintage same model. At different times he had shot probably every brand of ammo in that and a 20s vintage 94' .He stuck a case bad enough to need a smith to get it out 3 times in the newer rifle ,mean while the older rifle just ''chewed em'up and spit em' out'' . In that case it was a particular brands brass that just would not talk to that rifle. The solution was to simply not shoot PMC in that rifle.

I can not comment too much on this other than to say the 80s and 90s were not Winchesters' finest hour. To add further I haven't had issues with my 1903 and 1913 Winchesters, but then neither have I with my 1996 30-30. I can't take any chances that this is a brass issue, when using a load reduced below manual!



I wish you were close enough to come by the shop. We could scope that rifle and do a chamber cast.
Without seeing it, I hesitate to give an opinion, but the thought that is running through the back of my mind is perhaps a rung chamber (let's hope not).
I agree with the advice here. Either go see your smith, or buy a borescope and some cerosafe.
Sorry this is happening to you.
The one thing I would like to suggest (rather adamantly but with respect) is that you fire this gun no more till you have a very clear explanation of the trouble by a professional.
When things are not going right, its the rifles way of warning you that something may be seriously wrong, and should never be ignored.

I wish you were close enough too, I only know of one smith in this city and he is normally so busy its 10+ weeks before he will get around to looking at it.

Well I measured all the cases I have fired through the 375W, in terms of length and diameter there was nothing abnormal about the offending case.

Look at these pictures however, something is wrong visually.

113407

I don't know if this picture is good enough for you to spot the odd one out?


113408

The offending case.


113409

One of the other fired cases!

[44man]

Blow the boolit out with the primer, then the small charge ignites with a boolit in the bore. Can you say S.E.E? Lucky the Marlin did not come apart. Keep trying! Eventually you will get there. You can only dance with the devil so long before he takes you.
The shotgun pattern shot shows something is wrong.
Small charges can scatter all through the case from the primer but powder must be in contact so it ignites other grains, goes off better packed behind a stuck boolit.

[243winxb]

A buildup/mix of soot, lube and lead forming in the chamber throat/leade/barrel .

[44man]

A buildup/mix of soot, lube and lead forming in the chamber throat/leade/barrel .
Never seen that, a boolit should remove everything ahead of it. I did see lead on the cones and outside of revolvers when I cleaned guns for the Cleveland police at the club. Dead soft wad cutters in the .38. Front of cylinders and frames packed with lead squirted from the gaps. ever try to remove leading without harming the blue? Make the stinking boolit hard enough to resist rifling turn and maintain the same shape you cast. Lead in the cone or outside means slump. Gas cutting from a skidding boolit will lead the bore. To tell a guy to shoot "softer" to obturate is wrong. never works. Hard boolits do not lead bores. Softer gives me fliers. I have never shot air cooled as good as water dropped either.
Worst ever were coated pure boolits, made a rusted iron pipe of my bore. 50-50 NEEDS a GC and even though they did not lead my bore, accuracy was sad.

[Larry Gibson]

Is there a difference in case length with the offending case?

Larry Gibson

[andym79]

Blow the boolit out with the primer, then the small charge ignites with a boolit in the bore. Can you say S.E.E? Lucky the Marlin did not come apart. Keep trying! Eventually you will get there. You can only dance with the devil so long before he takes you.
The shotgun pattern shot shows something is wrong.
Small charges can scatter all through the case from the primer but powder must be in contact so it ignites other grains, goes off better packed behind a stuck boolit.

I will cease dancing with the devil! This was the canary in the mine for me!

That is just the thing though, the offending load was actually from the purple group that shot well!

What do you thing made that case look ugly?

As stated above "Well I measured all the cases I have fired through the 375W, in terms of length and diameter there was nothing abnormal about the offending case."

However the case looks different at the mouth!

[sthwestvictoria]

Blow the boolit out with the primer, then the small charge ignites with a boolit in the bore. Can you say S.E.E? Lucky the Marlin did not come apart.

44man could I challenge that statement while happy to be corrected? My understanding is that SEE is a risk with low load density of slow powders (to my mind slower than AR2206/H4895) and that we as cast/reduced load shooters are happy to reduce faster powders like H4895 H4227,2400 Unique and down to Reddot and bullseye. The powder presented as being used here was N110, given as being a similar burn rate to 2400 which many shooters use at reduced loads.

It is in vogue to label every over-pressure event SEE however that mental shortcut may stop us thinking about other causes. We know that double and over charges (http://castboolits.gunloads.com/showthread.php?81302-Swedish-m-96-KaBoom!) or powder contamination (http://castboolits.gunloads.com/showthread.php?147690-Blew-up-a-gun-Thursday-now-tell-me-WHY)/substitution (http://www.thefirearmblog.com/blog/2014/08/11/scope-saves-owner-improper-powder-load/) are more common.

From the ADI reloading handbook:
http://i62.tinypic.com/2vwhcpk.jpg



The shotgun pattern shot shows something is wrong.

Exactly and that altered pattern is very different with the first purple group he shot. There must have been a substantive alteration in some form and a substituted powder or altered load is a possible solution. If this was a SEE situation, how could there be a lovely group like that purple one on the first range trip and such a shotgun the second visit to the range?





As I said no more N110 or 379" projectiles for this rifle. 376-377" and my trusty H4227 or H4198 from now on.

I think we all agree no more N110! However the sizing question I am less clear on? Most shooters here feel if the bullet will chamber it is fine to fire. More experienced shooters should chime in however this overpressure event was not just due to .002" oversize cast bullets.

[Artful]

http://www.eabco.com/VihtaVuori01.pdf

N110

The fastest burning rifle powder from Vihtavuori. Similar to Hodgdon H110 and Winchester 296.
N110 can be used in small rifle cases like .22 Hornet and .30 Carbine but also
in magnum pistol and revolver cartridges like .357 S&W Magnum,
.41 Magnum, .44 Magnum, .454 Casull and .500 S&W.


they don't have a listing for 375 big bore - but do show one load in 444 Marlin - nothing in 45-70 for that powder

[Janoosh]

Going back to the original post, a fired case was chambered and extracted three times with no problem, on the fourth chambering the rifle locked up and there was hard extraction. If there is no marking or scarring on the case, the problem is with the firearm. Check for loose screws and/or scarring on the mechanical parts.

[bbqncigars]

Another possibility is something I saw with very reduced cast loads in 45-70. The outside neck area of some cases showed lead deposits. I can only guess that ignition kicked the boolit out of the case, and the burning powder gas cut lead which condensed on the brass. That area of the chamber looked fine, the brass was slightly sooty (showing too low pressure to seal)with some exterior lead plating. Those also were kinda sticky to extract, and NOT accurate. Too little of the wrong powder can be bad.

[44man]

44man could I challenge that statement while happy to be corrected? My understanding is that SEE is a risk with low load density of slow powders (to my mind slower than AR2206/H4895) and that we as cast/reduced load shooters are happy to reduce faster powders like H4895 H4227,2400 Unique and down to Reddot and bullseye. The powder presented as being used here was N110, given as being a similar burn rate to 2400 which many shooters use at reduced loads.
Not so. it can happen any time. too much air space and boolt movement before ignition. A primer with 2000# of pressure can drive a boolit well into the bore before lighting the powder. Sometimes powder will not even light and will pack behind a stuck boolit. Starting loads of 296 with a SR primer in the .454 stuck boolits with no powder burn. To use a large case with a pinch of powder is folly. Unique and 2400 in a 45-70 is junk. To use a pinch in the .375 is also junk.Go under starting loads is foolish.
Why in hell does cast need a pinch of shotgun powders?

[aspangler]

44man could I challenge that statement while happy to be corrected? My understanding is that SEE is a risk with low load density of slow powders (to my mind slower than AR2206/H4895) and that we as cast/reduced load shooters are happy to reduce faster powders like H4895 H4227,2400 Unique and down to Reddot and bullseye. The powder presented as being used here was N110, given as being a similar burn rate to 2400 which many shooters use at reduced loads.
Not so. it can happen any time. too much air space and boolt movement before ignition. A primer with 2000# of pressure can drive a boolit well into the bore before lighting the powder. Sometimes powder will not even light and will pack behind a stuck boolit. Starting loads of 296 with a SR primer in the .454 stuck boolits with no powder burn. To use a large case with a pinch of powder is folly. Unique and 2400 in a 45-70 is junk. To use a pinch in the .375 is also junk.Go under starting loads is foolish.
Why in hell does cast need a pinch of shotgun powders?
2400 is NOT JUNK in the 45-70. My load is 25 gr 2400 behind 405 fn for 1450fps average and es 6fps. also it is deadly accurate.

[44man]

2400 is NOT JUNK in the 45-70. My load is 25 gr 2400 behind 405 fn for 1450fps average and es 6fps. also it is deadly accurate.
Tried it from my BFR 10" Sad, 4759 will do under 1/2" at 100. 3031 will make a one hole group at 50 yards with a 45-70 rifle. My revolver does 1632 fps with 4759. 2400 will never be as good as 3031.
But 4227's and 5744 also suck. 4198 works with jacketed in the revolver but will have pressure spikes with cast to over 1800 fps. 3031 has less recoil then 4198 in a rifle but will not burn in the revolver.
i have rifle calibers in handguns but rifle powders work best. Do you know Varget works in the 7BR and 7R from 10" barrels.
Went through all the junk with my 30-30 marlin to find under 1" at 100 with 3031. 2400 WAS a joke.
2400 in a 45-70---naw. why not in a .300 Weatheby? .44 loads in a 45-70. Why did you buy a rifle to shoot pistol loads?

[WALLNUTT]

Can't get into the argument of WHY,all just theory. But I will say you can ring a chamber with fast powder. I rung a 30 30 AI chamber with 10gr of Herco and a 180gr cast bullet. I won't load anything like that again. Ring was in the neck at the base of the seated bullet.

[44man]

Can't get into the argument of WHY,all just theory. But I will say you can ring a chamber with fast powder. I rung a 30 30 AI chamber with 10gr of Herco and a 180gr cast bullet. I won't load anything like that again. Ring was in the neck at the base of the seated bullet.
Yes, it hurts to see damage done. How little it takes. i hate to read "I do it all the time" Accuracy is good! If ice is 1" thick and I told you it is safe, would you go on the lake? I really worry about some guys.

[andym79]

44MAN I get the impression that you don't like cast bullets or fast powders!

I generally like to try and fill at least 2/3 of a case but that isn't easy often. Maybe the cases are too large for cast. We need the opposite of AI, cases with reduced capacity for cast shooting. Take my 6.5x55 I would be happy if it was a 6.5x45 Swedish Mauser! A lot of the lever guns were obviously designed for black powder and that is the powder that fills the cases nicely. I am going to start using 55 grains of BP in my 375W and 30 grains of BP in my 30-30. I wonder how it would work in the Swede? These smokeless powders just have too much energy, there is too much choice and they are unpredictable.

I would use it, but it would sure make cleaning a chore!

I am sure SEE occurs and that it is a start-stop event. the bore is obstructed and the pressure has nowhere to go. Can powders as fast as 2400 really not ignite quickly enough to prevent a SEE?

I have read of the possibility of detonation with small amounts of fast powder. I am not 100% convinced as the analogy of a granary explosion has some holes.

How many grains of powder does it take to destory an action?

Smokeless powder is essentially all the same apart from shape and retardants. A 35 grains load of H4831 all going off at once has got to have a lot more energy than a little Red Dot hasn't it?

I read that SEE can be repeated around 20% of the time with slow powders. From that I think there must be another factor other than less than great ignition, like an eroded or leaded throat or a case to long that acts like a crimp because it is forced too deep into the chamber.

What work has been done to show the repeatability of detonation with fast powders like Unique and 2400? I am unsure, in any case aren't thes powders too fast to have delayed igniton that would be dangerous pressures?

Perhaps N110 has traits of both 2400 and H110. The powder is used extensively for reduced loads in Europe (granted apart from on independent source it was not listed for the 375W) but it is for cases from the 22 hornet to the 45-70.

With a fast powder filling half the case is we hypothesis, what could cause destruction of an action?

[WALLNUTT]

30 30 was never factory loaded with BP. My 30 30AI ended up shooting quite well with a case full of IMR4831 under the RCBS 180SP.The chamber was salvaged by polishing the ring. Extraction was only a little sticky.

[andym79]

I say with sarcasm, I have no intention of using BP, 44man just seems to hate air space in a case more than I do.

I know a lot of people would wouldn't consider 2400 junk for cast!

I do however agree with 44man that H4198 and H4895 are probably much better choices than Red Dot, Unique, 2400 and even H4227!

I have revisited trusted sources for data, and H4198 18 grains (approx 1390fps), H4895 25 grains (approx 1360fps) and H322 24 grains (approx 1490fps) are the powders for reduced loads. The first two listed by Lyman and the last by the manufacturer!

Sensible powders with a reasonable fill!

[44man]

Andym79, we don't know if fast powders can cause an SEE. Saving grace might be a lower peak pressure.
I shoot all cast except the Swede, pitted bore and no mold yet anyway. I do hate air space. I use a lot of 4759, the powder was made for reduced loads by being very bulky to fill a case more but I reduced a 1/2 gr one time in the 45-70 and had a failure to ignite. I reduced for a heavier boolit and it was a mistake. Boolit and powder was up the bore. I am glad it did not light. Not to be expected with 4759.
It is why I use a standard primer in the .44, I swear a mag primer will move a boolit too soon. The gap saves a lot of revolvers. With the case tension I use and the crimp, you would think it is enough so why are groups three times larger with mag primers?
Same with a .454 when the SR primers of all kinds did not light starting loads of 296. Had to load max. Going to a cut down .460 case eliminated all problems but a mag LP primer is more accurate with the large case. However a Fed 150 ignited all loads.
We had SEE events in the Swede with almost max loads of 4831 because the bullets were not seated deep enough and came out too soon.
I truly believe most cast loads have boolit movement before ignition, you can tell by the target. Even old loads are not as accurate as fresh rounds, I think brass relaxes the grip.
Long brass can increase pressure but I do not believe you need .002" expansion of the neck because the neck does not expand before boolit exit. The neck does not "jump open" with the boolit in the way. I will never use an "M" die either, ruins tension. I load cast just like jacketed and use the same powders. Just why do you need to reduce pressure? Extend the pressure peak once the boolit is turning in the bore.
Yeah, reduce recoil, recoil is a brain game. Ever see any 30-30 load hurt? My 12# 45-70 will turn your shoulder black with BP loads.
You see two things dominate posts, some want the highest velocity and others want no recoil at all from big guns. More posts dedicated to milk toast stuff then I can count. Buy a .500 and want no recoil, you are nuts! Shoot your gun as intended and cast will do very good.

[WALLNUTT]

i don't know what happens inside a chamber or case after I pull the trigger other than it goes bang. I only know what I see. I have used lots of 2400,4198,4759,RL7,and some others in 3006,4570,3030,3040 with what I consider good success,no problems.Loads generate 1800fps or less.

[leadman]

Were the second batch of boolits from the same alloy as the first and aged the same? I have had softer boolits give me problems, usually when the were the same alloy but had not acquired full hardness yet.
If I want to go to velocities as slow as what you are trying for I use a faster powder like Unique.
I tend to use 3 different burning range of powders in a larger cartridge like the 30-30 up to the 30-06. Unique speed up to about 1,400 fps, 4759 speed from 1,400 to about 1,900 fps, H4895 or slower from 1,900 fps to full listed velocities. This seems to work well for me and usually gives me great accuracy and no ignition or pressure problems.

[texaswoodworker]

Shooting cast I tried all loads listed here and all failed big time. Sorry, Unique and so many powders were a huge loss. Went to jacketed loads with better powders and get less then 1" at 100 yards.
What is it about cast that makes guys use the wrong powders?

Well for one thing pistol powders like Unique are great for light cast loads. Using Unique and a 190gr bullet, I can get sub MOA groups out of my 30-06 with ease.

[texaswoodworker]

Can't get into the argument of WHY,all just theory. But I will say you can ring a chamber with fast powder. I rung a 30 30 AI chamber with 10gr of Herco and a 180gr cast bullet. I won't load anything like that again. Ring was in the neck at the base of the seated bullet.

Were you using a wad or filler?

[andym79]

Bullets were the same alloy and same batch.

[243winxb]

A light load will not expand the brass or seal. Unburnt power, lube and lead will bleed back along the case body. This may make extraction harder after a few rounds. Same as if you shot 38 specials in a 357 mag chamber, then switched to 357 mag ammo. They stick. http://media.midwayusa.com/productimages/880x660/Primary/516/516544.jpg

[Multigunner]

The true cause of SEE phenomena is very difficult to pin down. Perhaps there are several different causes that produce the same result.

I've been wondering if some propellant granules may fragment if theres air space in the case, the primer not igniting the propellent till the shock of the primer detonation has turned some portion of the granules into a fine powder.

Cartridges subjected to vibration can detonate with disasterous results due to the propellant fragmenting.

[303Guy]

we don't know if fast powders can cause an SEE.With fast powders and a SEE there is the suspicion of double charges. That's the problem with fast pistol powders in a large case. While the case absorbs the pressure, a double charge can slip in without notice. That's why I chose a faster shotgun powder - for its bulkiness. It was a bad choice in my opinion since I have had sticky cases from it and definitely not double charges. The velocity was subsonic as it was supposed to be and there was no sign of any pressure on the primers plus I practice a very rigorous loading sequence. The neck expanded into rust pits in the neck area. Normal full power loads do not do that. I'm with 44man in his disdain for fast powders in a rifle case. The problem is, what are we to do? The only bulky fast powder is too fast for many of our applications and the 'right' powders that are available are not bulky enough. There is one bulky medium powder I believe but I don't know which one it is.

Something to consider regarding double charges or missing charges, when one has been loading for many years and thousands of rounds, the chance of a slip up becomes quite real. I've told my story many times, that being firing an un-powdered round and thinking I has simply left a fired case in the chamber and chambering another round. The powder stopped the bullet from being pushed back into the case, preventing closing of the bolt. Had that been a smaller charge of fast powder I would had a kaboom (and I might have blamed it on a SEE). That's another danger of fast powders - double boolit loads!

[andym79]

I am starting to think that what happened to me might be the result of more than one factor! Brass that was not FL sized, I have been neck sizing only in the 30-30 for a long time and have no problem with this, even brass that is on its 12th firing and even when I use it on pigs, get off the whole magazine fast.

However the 375 is a straight case, which will behave differently.

I believe things that were done wrong:

1. Not the best powder (though its very much like 2400)
2. Reduced the load too much 17 grains was the listed (Trailboss would have been the mouse fart powder)
3. Didn't clean crud from my cases.
4. Used excessive lube (I normally pan lube, these were very heavily coated with alox)
5. Not cleaning the rifle in-between trips to the range.
6. Didn't FL size my cases.

[WALLNUTT]

No wads or fillers. Always check powder level in cases before seating bullets. Call me crazy but I don't use shotgun or fast pistol powders in rifle cases anymore. I will however use 2400 but have better results with RL7,5744,4198 and 4759. Getting off subject of OP. Sorry. After he stated cases were dirty(lube covered?) chamber dirty(lube) I vote for thrust against bolt face from tapered case/chamber.

[RPRNY]

I will never advocate below minimum book loads for any powder. I don't care what someone says.
If you want better results from a large case, go to slower powders and stop fooling with pistol or shotgun powders. I would be using the 4895 or 3031 range, Varget too.
What in the world prompted you to use N110? It is faster then H110. That is a big bore, not a pellet gun.

You are entitled to your opinions but not to present them as facts. N110 is an excellent cast bullet powder with performance similar to 4227. While it may be situated near H110 on a burn chart, they are entirely different powders and they perform differently. N110 is an excellent performer with cast bullets from 30 cal through 444 Marlin.

[sthwestvictoria]

N110 is an excellent cast bullet powder with performance similar to 4227. While it may be situated near H110 on a burn chart, they are entirely different powders and they perform differently. N110 is an excellent performer with cast bullets from 30 cal through 444 Marlin.
Given your experience with N110, do you have a hypothesis about this overpressure event?

[Yodogsandman]

I don't think this was an overpressure event at all. I agree with some earlier posts, all put together they make sense.

At the point of the firing pin hitting the primer, the case was pushed slightly forward to the maximum chamber length, burnishing the mouth (see the shiny mouth edge). The primer went off and the powder ignited as it's supposed to.

The case expanded and tried to grab onto the chamber walls. Excess case lube build up prevented the case from grabbing and the case was thrust back against the bolt head before it could grab and hold the chamber wall. The case expanded with the full thrust back against the bolt and stayed there(see the smear of soot just forward of the case web). This situation was made worse by the neck sizing only. The case web was expanded from prior firings and was not resized to proper shape. Excess crud in the chamber and on the case helped, also. This caused the hard extraction. A lever action has a weak bolt extraction when compared to a bolt action.

Poor accuracy could have been caused by the loss of the pan lube residue left in the barrel being used up by prior firings. The heavy use of LLA changed the lubricity of the boolit in the travel up the barrel and exiting. This changed the rate of the build up of pressure behind the boolit causing the powder to burn at a little different rate (faster or slower). The boolit moved up the barrel at a faster or slower rate of speed also, throwing off the harmonics of the barrel. Depending on the stickiness of the LLA, the boolits could have also picked up some crud from the action and brought it into the chamber, too.

[303Guy]

The case expanded and tried to grab onto the chamber walls. Excess case lube build up prevented the case from grabbing and the case was thrust back against the bolt head before it could grab and hold the chamber wall. The case expanded with the full thrust back against the bolt and stayed there(see the smear of soot just forward of the case web).Actually, no, it doesn't quite work that way. Lube doesn't prevent case wall grip but does reduce it so the cases won't stretch to failure point at the web, instead it spreads the stretch over the length of the case, placing the load on the bolt face which is designed to carry the thrust of firing. More importantly, it allows the case to settle back earlier in the pressure curve thus reducing shock loading to some extent. There is something else going on like crud build up or case elongation (which I wouldn't expect if there is case lube on the cases). I have had hard extraction from dirt in the chamber.

[sthwestvictoria]

I don't feel the case/lube/neck sizing issue explains the situation and therefore pressure seems to be a more likely candidate. This is because the first purple group was such a nice consistent five shot string without any extraction problems. Two days later the shots are spraying around the target then a hard to open bolt. We have all seen how too much pressure destroys accuracy in cast by causing bullet slump/rifling skid (choose favourite theory).

Andy states all the case and bullet preparation was the same time to time:

I wish I knew why the second loading was so different! Powder was the same, charge was the same, lube the same, same alloy, same projectile, same brass cases, same primers. Even the weather conditions including temperature were the almost the same.

No I didn't check velocity the second time around as the ES was low between rounds the first time! Wish that I had now. The only thing I can say and I cant really described it adequatley but the recoil and noise felt/seemed different from two days earlier!

[44man]

I still don't buy into reducing N110, How far can you take it from the flame front of the primer. VV states it is like H110 and is for small rifle calibers like the 30 carbine and .22 Hornet.

[andym79]

I still would like a definitve answer on how the same load caused no problem and then two days latter caused a problem!

Is build up of lube and lead really a probable cause?

I really wish powder manufacturers would make more powders like Trailboss only with a slower burn rate (say the speed of H4198 but bulky).

[Yodogsandman]

I'd clean everything up and try it again to find out. That was a sweet load!

[RPRNY]

Given your experience with N110, do you have a hypothesis about this overpressure event?

I don't think I have enough information to diagnose the situation from the OP. I can say that in my experience N110 is more like 4227 than H110, that it performs well in a reduced load with cast bullets, and that I have had no experience with reduced loads that match those of the OP. Double charge? I don't know. It seems that brass and chamber issues could be at fault but I couldn't say.

[Driver man]

I had a Finwolf once that had a similar problem. Turned out to be the case crimping onto the boolit when loaded. I was using neck resized brass . Happened occasionally after several firings. Trimming the brass a mite solved the problem. Was a real pain in the rear trying to get the cases out in the Finwolf as they are a rotating front locking lever gun.

[303Guy]

I really wish powder manufacturers would make more powders like Trailboss only with a slower burn rate (say the speed of H4198 but bulky).Me too. It seems that for now we are kinda stuck with ultra slow powders under a heavy boolit but that costs more since we would have to use so much more of it.


I had a Finwolf once that had a similar problem. Turned out to be the case crimping onto the boolit when loadedThe thought crossed my mind. I have one Brit in which I discovered the test case was beginning to enter the throat. The mouth had a small inward taper indicating it was too long. A boolit would still enter it so it wasn't causing a problem in my case.

Thinking on this problem I'm wondering whether the chamber might be a bit rough and is occasionally (depending on the degree of dust/carbon or whatever in the chamber would sometimes allow the case to creep and elongate elastically to take up headspace clearance and other times grip it fast so that the case would undergo plastic deformation and thereby locking the bolt. That might explain the different behaviour of the same load on different days. The chamber has been cleaned and dried between. Or the cases may have dried or been dried on the second occasion. Then again it may have nothing to do with it.

[44man]

I have been shooting the 30-30 and found I have to trim after every shot from bolt stretch. I do not FL all the way, just to good bolt closure. Some brass does not touch the cutter but all are run through. Some get cut a lot.

[303Guy]

You're a candidate for my trick. That trimming will go away. Something else, now one really loads to the maximum of the bolts load capacity - not with cast boolits anyway. That's something I make sure of, that I'm well below the allowable level with my loads.

[Tar Heel]

I wish you were close enough to come by the shop. We could scope that rifle and do a chamber cast.
Without seeing it, I hesitate to give an opinion, but the thought that is running through the back of my mind is perhaps a rung chamber (let's hope not).
I agree with the advice here. Either go see your smith, or buy a borescope and some cerosafe.
Sorry this is happening to you.
The one thing I would like to suggest (rather adamantly but with respect) is that you fire this gun no more till you have a very clear explanation of the trouble by a professional.
When things are not going right, its the rifles way of warning you that something may be seriously wrong, and should never be ignored.

Ditto.....and downloading that propellant (and others) is a disaster waiting to happen. It's called a pressure excursion and trust me, you don't want one.

[44man]

You're a candidate for my trick. That trimming will go away. Something else, now one really loads to the maximum of the bolts load capacity - not with cast boolits anyway. That's something I make sure of, that I'm well below the allowable level with my loads.
I am not loading hot, Seems to be brands of brass, some cases never need trimmed. I used mixed brands because all my brass are pick ups.
My boolit weighs 187 gr and loves 25 to 26 gr of 3031. Gives me about the same velocity as 18 gr of 4759 with the 150 RCBS but far more accurate.
I have had some good groups with 4895 and Varget but can't duplicate them.
My Remlin seems to prefer a heavier boolit. My boolit will stay under 1" with 3031, been to 5/8" and three shots in 5/16" at 100 yards. Recoil is almost nothing, just need to hold the forearm and rest my hand on the bag, wood on the bag will not group. Even getting the barrel hot maintains groups and POI.
I bought the book telling how to make guns accurate but the drastic stuff done is crazy since the gun shot right out of the box. Only thing I did was to improve the trigger.
Far cry from the stupid twist in the .44 mag, prettiest but worst shooting lever gun I ever had. They used Greenhill to use the 1 in 38" twist. I think a RB might have worked!

[andym79]

Hi guys, I bought a cheap bore-scope.

I apologise that the picture isn't that good, but here are two videos of my Winchester (375W) 94s chamber.

The first is a corkscrew pass https://www.youtube.com/watch?v=XQ6ukOy19DM

The second is four passes along the chamber about 90 degrees from each other https://www.youtube.com/watch?v=5uS5fK1qfpA

Even with the poor image does anything look wrong?

[44man]

Darn, nice tool. That barrel must have been made in Spain!

[sthwestvictoria]

Hi guys, I bought a cheap bore-scope.
I apologise that the picture isn't that good, but here are two videos of my Winchester (375W) 94s chamber.
Even with the poor image does anything look wrong?

Great videos! Amazing when you get that close look at something that is so hard to look at with detail like the rifling. There does seem to be a lot of tool marks in the chamber but I have not experience about bore scopes and machining chambers so maybe that is quite normal! Do your other chambers look like that? The apparent roughness is probably just a factor of magnification. Very interesting, thanks for taking the time to record and load it up.

[andym79]

Great videos! Amazing when you get that close look at something that is so hard to look at with detail like the rifling. There does seem to be a lot of tool marks in the chamber but I have not experience about bore scopes and machining chambers so maybe that is quite normal! Do your other chambers look like that? The apparent roughness is probably just a factor of magnification. Very interesting, thanks for taking the time to record and load it up.

It does look rough and I hope it is just magnification. I will scope the Winchester 94 30-30 tonight as its the closest being another 94!

[303Guy]

And now we can see why light case lubing won't prevent case to chamber wall grip. I don't think I'll allow a bore scope into my 303 Brits chamber or bore cause I won't be able to sleep again!:mrgreen:

I wonder how much polishing would occur by firing cases smeared with AutoSol? I know the cases come out shiny as.

[Yodogsandman]

I'm no expert but, I'd be encouraged by those video photos. I've seen pictures of rotten bores and yours looks pretty good. I saw little pitting and no scaling, heat checking or craising. Not sure if the tool marks are normal but, they could be for a mass produced rifle.

[andym79]

Here is a link to the 30-30 chamber for reference
https://www.youtube.com/watch?v=_Wwvm6wxcjo&list=UUqqAQIrECJlD4Wu2XxBHFMQ&index=1

Its not much different!


Here if the bore of the 375W from chamber to muzzle

https://www.youtube.com/watch?v=83wB0vfm8m4&list=UUqqAQIrECJlD4Wu2XxBHFMQ

The bore looks good!


Here is the bore of my 1903 M92 in 38-40

https://www.youtube.com/watch?v=gjAzRF9PL6E&feature=youtu.be

I feel dirty after looking at it poor rifle deserves a new barrel, it still shoots well though!

[trixter]

So if I decide to use a brush for cleaning the chamber, and I mount it to cordless screwdriver that is variable speed, and turn it slowly (very slowly) will there be any damage?

[44man]

So if I decide to use a brush for cleaning the chamber, and I mount it to cordless screwdriver that is variable speed, and turn it slowly (very slowly) will there be any damage?
No, just don't use a stainless brush, Nylon or bronze is fine.
You don't want a dead polished chamber anyway, increases head pressure to the bolt. Some full autos have flutes in the chamber to retard extraction.

[303Guy]

Some full autos have flutes in the chamber to retard extraction.Actually, it's the other way around. The purpose of the flutes is to allow combustion gasses to float the case to facilitated extraction while under high pressure. Without those flutes the cases have difficulty extracting.

Too high case to chamber wall grip is not desirable and can cause hard bolt lift. It can also increase shock loading to the bolt face (when the gripped case suddenly slides back under high pressure as opposed to settling back at lower pressure). Some folks polish their rifle chambers by spinning a fired case with Flitz on it, using a drill. I can't comment on that as I have never done it but from what I can remember it stops case head separation and/or case elongation. One person has stated that he found polishing his rifle chamber resulted in stiff bolt lift which is opposite to what I am saying. He says he leaves his chambers as reamed and does not get stiff bolt lift. So I am giving you contradictory views. I have never had stiff bolt lift from low case grip but have from the case expanding into rust pits in the neck. I also don't load to 60,000 psi.

I'm of the opinion that consistent case wall grip is important for accuracy and that could be what is being achieved on target type rifles.

[andym79]

Back to the rifle in question does it chamber look normal or not?

[44man]

Actually, it's the other way around. The purpose of the flutes is to allow combustion gasses to float the case to facilitated extraction while under high pressure. Without those flutes the cases have difficulty extracting.

Too high case to chamber wall grip is not desirable and can cause hard bolt lift. It can also increase shock loading to the bolt face (when the gripped case suddenly slides back under high pressure as opposed to settling back at lower pressure). Some folks polish their rifle chambers by spinning a fired case with Flitz on it, using a drill. I can't comment on that as I have never done it but from what I can remember it stops case head separation and/or case elongation. One person has stated that he found polishing his rifle chamber resulted in stiff bolt lift which is opposite to what I am saying. He says he leaves his chambers as reamed and does not get stiff bolt lift. So I am giving you contradictory views. I have never had stiff bolt lift from low case grip but have from the case expanding into rust pits in the neck. I also don't load to 60,000 psi.

I'm of the opinion that consistent case wall grip is important for accuracy and that could be what is being achieved on target type rifles.
Never want a high polish in the chamber. But rough tool marks are not too good either.
You are wrong about the fluted chamber, it increases area to hold the brass long enough to reduce pressures before extraction. Flutes reduce head pressure and slow extraction. They are full auto guns mostly that would beat themselves to destruction. It was a fix to increase rate of fire without making springs stronger.

[303Guy]

I stand corrected then. I did get the information that it was a fix to solve the problem of the extractor tearing through the rims. Well, we live and learn. I was also wrong about never having stiff bolt lift with too smooth a chamber. I found an entry in which I did have stiff bolt lift with a lightly lubed case. I entered that pressure was too high and that there was cratering on the primer. OK, so I don't deliberately load to 60,000 psi! [smilie=1: And with cast too! :!: I think the max allowable for the Brit is 50,000 psi (43~45,000 CUP)

My 22 hornet has a rough chamber and that tears the cases in short time so I lube the cases well and that overcomes that problem. They do not have a neck to headspace on so I headspace them on the case mouth.

[Larry Gibson]

303Guy is correct; "Actually, it's the other way around. The purpose of the flutes is to allow combustion gasses to float the case to facilitated extraction while under high pressure. Without those flutes the cases have difficulty extracting."

The fluted chamber was developed by German engineers to provide reliable functioning with full power NATO spec 7.62 ammunition in the CETME rifle. Simple research the history of that rifle and you'll find the reason. Chamber fluting was carried over in the H&K series of rifles and a few others.

Larry Gibson

[44man]

303Guy is correct; "Actually, it's the other way around. The purpose of the flutes is to allow combustion gasses to float the case to facilitated extraction while under high pressure. Without those flutes the cases have difficulty extracting."

The fluted chamber was developed by German engineers to provide reliable functioning with full power NATO spec 7.62 ammunition in the CETME rifle. Simple research the history of that rifle and you'll find the reason. Chamber fluting was carried over in the H&K series of rifles and a few others.

Larry Gibson
OK, I might be wrong with what I read about them. But how do gasses "float" a case? Only thing I can see is to dissipate chamber pressure by enlarging the expansion area.
Remember the .22 Jet in the S&W revolver? Needed to lube brass or they stuck. Why have billions of full autos been made without flutes.
Last I read was for flutes to retard bolt open just enough.
Give me a link.

[WALLNUTT]

How would chamber flutes increase area of contact?

[fouronesix]

Don't dispair 303Guy- yes you are mostly right. This same nonsense of a conspiracy about H&K hiding the truth about the fluted chamber has been circulating the net for at least a couple of years. But there are those on the web who love and live for conspiracies, black helicopters and men in black. Those are the same ones who always seem to have a secret truth.

[44man]

How would chamber flutes increase area of contact?
Expand into flutes that increases brass contact with chambers. Should double brass contact.
I might be right about more resistance to head pressure.
I have not come to terms of "float".

[Harter66]

The fluted chambers were intended to allow the rifles to run longer cooler and dirtier . The chamber fluting actually reduces wall contact area. And increases surface area to be heated. Most of them start about .1 from the case mouth . The H&K 92 was intended to run in the desert w/lots of sand but mud also . It was determined tha t an overall tight therefore accurate chamber could be had and still feed dirty , rusted ammo. Kind of like the sloppy AK and SKS.

[44man]

Beware of Commercial .308 and Fluted Chambers Posted April 30, 2013 in News (http://www.thefirearmblog.com/blog/category/news/), Other Gear & Gadgets (http://www.thefirearmblog.com/blog/category/guns-gear/other-gear-gadgets/), Rifles (http://www.thefirearmblog.com/blog/category/guns-gear/rifles/) by Alex C. (http://www.thefirearmblog.com/blog/author/alex-capps/) with 84 Comments (http://www.thefirearmblog.com/blog/2013/04/30/beware-commercial-308-fluted-chambers/#disqus_thread)

1810
0*0
*1 7
http://www.thefirearmblog.com/blog/wp-content/uploads/2013/03/case2.jpg
My good friend CJ is a real whiz at building H&K roller locked stuff. Back in the day when G3 parts kits were affordable and flowed into the United States like water anyone could build one for a few hundred bucks. The problem however (aside from relative build difficulty) was that a true G3 spec chamber does not like commercial .308 Winchester ammunition. G3 rifles have an internally fluted barrel. This aides in extraction and prevents the possibility of an extractor breaking, and a shell sticking. The gas from the discharge is forced back and around the spent shell blowing it out of the breech. So, in the event an extractor breaks, or some ammunition failure, you will definitely get the spent case out of the weapon. With no extractor at all it will eject a round, or at worse cause a partial ejection which requires you to pull the cocking handle and drop the round out. The problem with this is it mangles brass. CJ found this out the hard way:
http://www.thefirearmblog.com/blog/wp-content/uploads/2013/03/case.jpg (http://www.thefirearmblog.com/blog/2013/04/30/beware-commercial-308-fluted-chambers/case-2/)
What you see here is what can happen. This was commercial .308 fired in a properly built G3; It is very dangerous and can kill you. You must use 7.62×51 NATO if you have a true G3 spec barrel. As you can see, the top of that round has the aforementioned flute marks – that’s what a spent shell looks like – it gets ruined. Now, if you notice… that’s only 1/3 of a shell, the rest of it was ripped off. Since commercial .308 is much thinner cased, when the round discharges the more pliable case expands and actually sticks in the flutes, and given the power of the round, the extractor literally rips the back of the case off, leaving the front of the shell stuck in the barrel. The next round was cycled in with such force, it actually slid itself through the remaining case neck. Luckily CJ noticed the rifle wasn’t in full battery and didn’t fire it (that would have been catastrophic).
H&K 91 rifles had a much looser chamber to allow the firing of .308 ammunition, and modern manufacturers of G3 pattern rifles seem to have adopted a similar chamber. Just beware of what can happen and be safe!

- See more at: http://www.thefirearmblog.com/blog/2013/04/30/beware-commercial-308-fluted-chambers/#sthash.J3SO42Fi.dpuf
A few things.
Beware of Commercial .308 and Fluted Chambers Posted April 30, 2013 in News (http://www.thefirearmblog.com/blog/category/news/), Other Gear & Gadgets (http://www.thefirearmblog.com/blog/category/guns-gear/other-gear-gadgets/), Rifles (http://www.thefirearmblog.com/blog/category/guns-gear/rifles/) by Alex C. (http://www.thefirearmblog.com/blog/author/alex-capps/) with 84 Comments (http://www.thefirearmblog.com/blog/2013/04/30/beware-commercial-308-fluted-chambers/#disqus_thread)

1810
0*0
*1 7
http://www.thefirearmblog.com/blog/wp-content/uploads/2013/03/case2.jpg
My good friend CJ is a real whiz at building H&K roller locked stuff. Back in the day when G3 parts kits were affordable and flowed into the United States like water anyone could build one for a few hundred bucks. The problem however (aside from relative build difficulty) was that a true G3 spec chamber does not like commercial .308 Winchester ammunition. G3 rifles have an internally fluted barrel. This aides in extraction and prevents the possibility of an extractor breaking, and a shell sticking. The gas from the discharge is forced back and around the spent shell blowing it out of the breech. So, in the event an extractor breaks, or some ammunition failure, you will definitely get the spent case out of the weapon. With no extractor at all it will eject a round, or at worse cause a partial ejection which requires you to pull the cocking handle and drop the round out. The problem with this is it mangles brass. CJ found this out the hard way:
http://www.thefirearmblog.com/blog/wp-content/uploads/2013/03/case.jpg (http://www.thefirearmblog.com/blog/2013/04/30/beware-commercial-308-fluted-chambers/case-2/)
What you see here is what can happen. This was commercial .308 fired in a properly built G3; It is very dangerous and can kill you. You must use 7.62×51 NATO if you have a true G3 spec barrel. As you can see, the top of that round has the aforementioned flute marks – that’s what a spent shell looks like – it gets ruined. Now, if you notice… that’s only 1/3 of a shell, the rest of it was ripped off. Since commercial .308 is much thinner cased, when the round discharges the more pliable case expands and actually sticks in the flutes, and given the power of the round, the extractor literally rips the back of the case off, leaving the front of the shell stuck in the barrel. The next round was cycled in with such force, it actually slid itself through the remaining case neck. Luckily CJ noticed the rifle wasn’t in full battery and didn’t fire it (that would have been catastrophic).
H&K 91 rifles had a much looser chamber to allow the firing of .308 ammunition, and modern manufacturers of G3 pattern rifles seem to have adopted a similar chamber. Just beware of what can happen and be safe!

- See more at: http://www.thefirearmblog.com/blog/2013/04/30/beware-commercial-308-fluted-chambers/#sthash.J3SO42Fi.dpuf
Beware of Commercial .308 and Fluted Chambers Posted April 30, 2013 in News (http://www.thefirearmblog.com/blog/category/news/), Other Gear & Gadgets (http://www.thefirearmblog.com/blog/category/guns-gear/other-gear-gadgets/), Rifles (http://www.thefirearmblog.com/blog/category/guns-gear/rifles/) by Alex C. (http://www.thefirearmblog.com/blog/author/alex-capps/) with 84 Comments (http://www.thefirearmblog.com/blog/2013/04/30/beware-commercial-308-fluted-chambers/#disqus_thread)

1810
0*0
*1 7
http://www.thefirearmblog.com/blog/wp-content/uploads/2013/03/case2.jpg
My good friend CJ is a real whiz at building H&K roller locked stuff. Back in the day when G3 parts kits were affordable and flowed into the United States like water anyone could build one for a few hundred bucks. The problem however (aside from relative build difficulty) was that a true G3 spec chamber does not like commercial .308 Winchester ammunition. G3 rifles have an internally fluted barrel. This aides in extraction and prevents the possibility of an extractor breaking, and a shell sticking. The gas from the discharge is forced back and around the spent shell blowing it out of the breech. So, in the event an extractor breaks, or some ammunition failure, you will definitely get the spent case out of the weapon. With no extractor at all it will eject a round, or at worse cause a partial ejection which requires you to pull the cocking handle and drop the round out. The problem with this is it mangles brass. CJ found this out the hard way:
http://www.thefirearmblog.com/blog/wp-content/uploads/2013/03/case.jpg (http://www.thefirearmblog.com/blog/2013/04/30/beware-commercial-308-fluted-chambers/case-2/)
What you see here is what can happen. This was commercial .308 fired in a properly built G3; It is very dangerous and can kill you. You must use 7.62×51 NATO if you have a true G3 spec barrel. As you can see, the top of that round has the aforementioned flute marks – that’s what a spent shell looks like – it gets ruined. Now, if you notice… that’s only 1/3 of a shell, the rest of it was ripped off. Since commercial .308 is much thinner cased, when the round discharges the more pliable case expands and actually sticks in the flutes, and given the power of the round, the extractor literally rips the back of the case off, leaving the front of the shell stuck in the barrel. The next round was cycled in with such force, it actually slid itself through the remaining case neck. Luckily CJ noticed the rifle wasn’t in full battery and didn’t fire it (that would have been catastrophic).
H&K 91 rifles had a much looser chamber to allow the firing of .308 ammunition, and modern manufacturers of G3 pattern rifles seem to have adopted a similar chamber. Just beware of what can happen and be safe!

- See more at: http://www.thefirearmblog.com/blog/2013/04/30/beware-commercial-308-fluted-chambers/#sthash.J3SO42Fi.dpuf

[44man]

Sorry things got tripled.

[44man]

Another one.

HK says it's to "aid extraction", but it's not true. It it retard the opening of the action.

HK has videos out there showing the P7 reliably ejecting cases without an ejector at all, and claims it is due to the chamber flutes.
The truth is: Any semi-auto gun will cycle reliably without the extractor. The case PUSHES on the bolt, the extractor doesn't PULL it. Some guns don't even have extractors, like the Beretta tilt-barrel pistols including the model 21 .22lr, and the Tomcat .32. And the open-bolt .22 rifles like the Gevarm and the Voere - no extractor.

The challenge is to RETARD the recoil of the empty case from opening the action too soon. Short of locking the bolt/slide to the barrel, there are a number of ways to do this. The simplest is inertia, just have the bolt heavy enough, so that by the time the recoil of the case overcomes the inertia, the bullet has left the barrel. However if you don't want that much weight in your gun, you can use a combination of inertia, and a fluted/grooved chamber. There have been handguns sold that rely on deforming the case into a grooved ring in the chamber to delay the opening of the bolt. The Seecamp pistol is an example;
"chamber-ring delayed, in which the fired case expands to seal the chamber walls and delay extraction--the Seecamp pistol operates in this manner;"
http://www.thefreelibrary.com/If+it+...d.-a0197482929 (http://www.thefreelibrary.com/If+it+can%27t+blow+back,+then+it+must+blow+forward .-a0197482929)
And this is what the HKP7 does. They put flutes in the chamber from where the bullet leaves back about 1/2 the length of the case. The ring formed where the flutes end provides the same effect as the ring in the chamber if the Seecamp. The case deforms into the groves and straightening out the deformations as they pass over the REAR end of the grooves, provides resistance to rearward movement

With the HKP7 the action is is partially case-deformation retarded, and partially gas retarded.
And the HK91 rifle works the similarly. The groves do not extend to the rear of the chamber. Look at this picture: http://www.weaponeer.net/forum/uploa...mber_halfs.jpg (http://www.weaponeer.net/forum/uploads/jestism/images/2008-02-20_153226_chamber_halfs.jpg)
The HK91 action is partially case-deformation retarded, and partially roller retarded
With the P7 there is a short time delay (= about 1/2" in travel of the bullet) between when the round is fired and when the bullet is far enough down the barrel to feed gas into the hole to operate the gas-delay piston. But that would be plenty of time for the action to open and render the gas-delay system usless. So to cover the first 1/2" of bullet travel, HK cut out a fluted ring in the first 1/2" of their chambers in their gas delayed pistols.

Then for the P7 they released the ridiculous lie about it was done to allow the gun to operate without an extractor! And for the HK91 they released the lie that the flutes were to stop the extractor ripping the base of the case off! Extractors never pull unless you are hand-cycling the action.
That's why HK P7s are ammo-sensitive. This is what happens with P7s when you use cases with the wrong deformation metalurgy:
http://chris.cc/p7m13.htm
[[The Mystery of the HK P7M13 and the COR®BON Ammo..
Loaded up some COR®BON 115 gr., fired about ten times and the last round did not extract from the chamber. ]]
Operation depends on the material the case is made of. Seecamp is honest enough to say their pistols will only work reliably with one specific brand of ammo - winchester silvertop. They have coordinated the depth of their chamber-groves to match predictable deformation.

The HK91 is less ammo sensitive than the P7 because it is less dependent on case-deformation retardation, and more more dependent on its other method of retardation (roller retardation).



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[44man]

Another Back in the 70's there were a lot of articles written about the Heckler and Koch rifles with the fluted chambers. Instead of conventional square locking lugs they used rollers in the bolt to lock it and they incorporated the flutes in the chamber to help delay the bolt from moving rearward until pressures were down to the proper amount. It is a well engineered system and is still used in their .223 and .308 rifles. Hk 92 an Hk 93's ? There were several articles about reloading the ammo and it was found that there was no problem with reloading the brass. It was just unsightly seeing the slight grooves remaining in the brass after resizing. Definitely tumble the brass! Inspect the brass for cracks etc. the same as you would normally do. If any of you are interested in a "battle" rifle that is accurate enough for varmints, buy an HK.!!!

Bob In St Louis

[44man]

Yes, some say gas goes outside the brass to the bolt to aid extraction,adding to bolt thrust, Float. Yet brass sticking at the back of grooves is still to retard head pressures. How is it explained?

[MBTcustom]

You learn something new every day. I had heard of the fluted chambers, but had no earthly idea of why they would do that. Very interesting.
Thanks 44man.

[shooterbob]

Could it possibly be leading a bit and now the larger boolits are causing a pressure spike?