Pressure signs in rifle cases.

[littlejack]

Hey members:
I have been working on loads with jacketed bullets in my m44 MN here lately.
As always, starting at a start load, and working up. Pressures look good to start, then slight flattening of primer, with the increase in powder. Then, a little more flattening as the powder charge is increased. Then, slight cratering of primer, and so on. I realize that when the primer is flattened to the point that there is NO radius around the perimeter, you got problems, and better back off.
Now, I have seen a lot of factory loaded ammunition fired, and resulted in the same flattened primers. I have also seen primers that had "cratered" with factory loaded ammunition. (Some of this could be from an enlarged firing pin hole) I have ALSO seen shiny spots from the ejector slots and plunger holes in the bolt face, with factory loads.
I know that using fired primer condition as a pressure indicator is sketchy at best.

Questions: So, with all that being said; At what pressures does the brass case start to flow into the ejector slots, or plunger holes in the bolt face?

I believe there are a few members here that have pressure testing equipment.
Has anyone done any extensive testing (with pressure testing equipment) regarding primer condition, to respective
known pressures?
Any input is greatly appreciated.
Thank you.

[leebuilder]

Hi littlejack
very interesting. I have encountered all of the above. I am only trying to help, i have no pessure measuring devices. But shoot mosins.
It is obvious that you have way to much pressure if the brass flows as you described! Primer condition is a good clue, thats all,, but you know that.
What powder are you using? I have mosin hand loads 2grs above suggested max loads with no pressure signs or excessive recoil and very accuate.
I think you may have barrel issues, slug and inspect. Seen mosins with crippeling dings in the barrel and tight spots. Plus you have a 44 with a short barrel in my mind this would lessin pressure, less time to build up as apposed to a long barrel.
any questions please ask
be safe

[Hannibal]

I stick with published data and leave experimentation to others, so I can not speak to your questions with personal experience. However, if you have not already studied it, Ken Waters did extensive load development testing on many calibers and his results are published in a 2 volume set titled 'Ken Water's Pet Loads'. In the first volume, he gives detailed instructions and examples of his methods of reading pressure signs. This might be of help to you.

[leebuilder]

Plus one on Ken Waters books, Hatchers notebook is a teasure trove of info too!!

[littlejack]

Thanks for the input fellas.
Every time I find a set of the Ken Waters books for sale, I am always too late. One of these days maybe.

Leebuilder, I use IMR 4064 for my MN loads. It works very well at getting good velocities, with the short 20" barrel, as the burn rate is not too slow as 4350 as some use for their longer barrels, and not to fast to cause pressure buildup to quickly . I load the Hornaday .312 150 grain sp to a chrony'd velocity of 2800+ a little. The bore of my m44 slugs at .313.
I believe, the most pressure build up is in the first few inches of the barrel, so as the bullet gets further down the bore, the pressure lessons, not increases.

[leebuilder]

I am stumped, i have used that powder.
your right about the pressure in the barrel and they are contoured that way, i agree that it lessons, still a lot of pressure in there.
I will do some reading and talk to the range silverbacks.
be safe.

[C.F.Plinker]

I don't have a Hornady book but Sierra shows IMR-4064 loads from 42.8 grains with a velocity of 2300 fps up to 48.5 grains with a velocity of 2650 out of an M44 with a 20" barrel. Lyman 48 doesn't show IMR 4064 at all. Their velocities for maximum loads using the powders they tested are in the low to mid 2700 fps range out of a 26 inch barrel. What pressure signs were you seeing at loads that chronographed in the 2550-2750 fps range?

Whose data were you using for your loads?

[littlejack]

C.F.P:
If only using primer condition (which we know if not very reliable) the only pressure signs with the 150 grain Hornaday bullets is slight flattening.
I have worked the loads up with the Hornaday bullet, and the 4064 powder to "above" listed powder weights. Again, no outstanding visual primer issues. No hard bolt lift. No enlarged primer pockets. I haven't thrown any cases away due to excessive pressures.
I was just "neck" sizing, but went to "partial sizing" There is a slight pressure when closing the bolt, so there is no headspace.
The chamber throat is .319, and the groove dimension is .313, which may be a couple of the reasons for the lower pressure signs using the .312 bullet.
I have reloading data that lists up to 49 grains of 4064 with the 150 grain bullets.

[leftiye]

Avoid the shiny spots (as stated). Back off until they disappear. The fact that you don't get pressure signs at or above manual loads isn't a problem. If the pressure isn't there - that's not a problem. Probly your gun creates lower pressures. A friend who was a gunsmith used to tell about customers who brought their guns back and complained that they could not put as much powder in there as their friends could in their guns (same caliber). He made tight chambers to start (better for a number of purposes) so he would just hand ream a bit out so these guys could use more powder.

Primers of various makers have different hardness/thickness of cups. Unless you know you have the hardest/thickest primer cups, a little flatness, even a bit of cratering isn't something to worry much about (I'd still back off). Blown primers usually don't damage the gun, or amount to a problem (but do back off or find the reason). CCI makes good tough, hard primer cups.

[B R Shooter]

Not anything to do with a MN, but I bought a new Savage 110 in 220 Swift years ago. Seemed like every load I tried flatened the bajebers of the primer. On a whim, I started neck sizing only, and it all disappeared. I could shoot any published load without any problem, and I never had to go back and full length size due to the brass getting tight, which proved the loads weren't excessive.

[littlejack]

I use Winchester primers exclusively. Not that they are better than others, but that they are readily available here locally, and function in my SDB press.
I use to use CCI exclusively years ago. I have heard and read that CCI primers are harder than other brands. With that being said, I read one time that a fella called back to CCI, and they told him that their primers were no harder than any others. I don't know if I believe that or not.
When I first bought my Dillon SDB back in the early 80's, I was using CCI primers. I was having a real hard time
seating the primers flush in the pockets.
I called Dillon, and they told me to switch to either Federal or Winchester. I did. Problem solved. Been using
Winchesters ever since.
I may have some other primers some where about. I may do some testing, and see if those primers and their
different make up, show a visual difference in their condition when fired.

[bearcove]

Not anything to do with a MN, but I bought a new Savage 110 in 220 Swift years ago. Seemed like every load I tried flatened the bajebers of the primer. On a whim, I started neck sizing only, and it all disappeared. I could shoot any published load without any problem, and I never had to go back and full length size due to the brass getting tight, which proved the loads weren't excessive.
This is important! Headspace is the major factor in primer flattening. NOT pressure. If you oversize your brass, ie excessive headspace, When you fire it it sets back against the bolt face. Hammers it flat. Higher pressure makes it more pronounced. No way you can predict overpressure. Proof test loads don't show flattening some times. Use load data that is pressure tested. Or buy more insurance...

[littlejack]

Not trying to argue, but, I "neck size" only all of my rifle cartridges. As I said earlier, I was only neck sizing the m44, but went back to "partial sizing". There is some flattening of primers with each of the individual cartridges I reload . I do stay within reloading book listed data, unless I feel that I can load that particular cartridge/rifle combination over the book data and be plenty safe.
As stated in my previous posts, a lot of factory ammunition will flatten primers to some degree, and leave bright marks on the case head. Does that mean that all of these rifle/cartridge chamberings, have headspace? If it does, there are a lot of people out there in danger.
When the bolts are closed on my rifles, there is a slight force necessary to get the bolt to cam down on a chambered round. This indicates that there is NO headspace, as the head of the case is tight up against the bolt face, and the shoulder of the case is tight up against the shoulder of the chamber at the datum line.
My brass is not oversized, so how can there be headspace?

[leebuilder]

Got a chance to bend a silver backs ear yesterday and did some reading. Still stumped, but reading the last few post and knowing the Mosin. There could be something to neck or partial sizing to lesson the problem.
mosins are headspaced on the rim, so it could gauge just fine
but it is a surplus gun and could have a "long" chamber or elongated chamber that is often found in 303s.
still reserching and learning.
Be safe.

[B R Shooter]

"When the bolts are closed on my rifles, there is a slight force necessary to get the bolt to cam down on a chambered round. This indicates that there is NO headspace, as the head of the case is tight up against the bolt face, and the shoulder of the case is tight up against the shoulder of the chamber at the datum line."

Good! Never go by what die makers say about hitting the bottom of a die to the shell holder. Take the striker out, then only resize enough so you have some feel. This might not work well in semiautos, but should be done in bolt guns. A couple thoughts, first, you still may have an oversize chamber and you are squeezing the body down quite a bit still oversizing the brass. It means at some point the brass is making contact in the chamber. Most often you are hitting the shoulder. Best case scenareo. In the Swift I was refering to, my dies were adjusted this way, but I still had the pressure signs. I think the brass was contacting the shoulder in the chamber, but the chamber was still big, and the brass couldn't swell and grip the walls as it shoud. WHen you can see the case has a "swell" just above the base, at the .200" above the head, this is where the walls begin and the solid base ends. The chamber is oversize for the brass. In a good chamber/brass fit, you never see that.

[bearcove]

Factory rifles tend to have headspace on the large size. Factory ammo tends to be sized to the small size. Makes it function reliably. Thats why some folks reload. Control of headspace usually by neck sizing, decreases deformation of your brass in the fire, size, fire, size cycle, making it last longer.

We are talking about quantifying pressure based on a deformation of the case head. You can do this to some degree if you control ALL the other variables. Considering outside of a machine shop/lab most can't do this, deciding how high the pressure based on the appearance of the case head seems a risky method.

If you check a rimmed cartridge rifle you find it also has slop. Littlejack if you necksize then you can get better indications of pressure. How much? Who knows? All rifles will give different pressure depending on dimensions and smoothness of the chamber throat and barrel

[littlejack]

Nise:
I don't understand? --------------"the neck was short and caused excessive neck tension"??????????????
Did you mean, "the necks were LONG and caused excessive neck tension"?

[flounderman]

As long as the brass chambers, there is no good reason to full length size it. Half to 3/4 of the neck is all that is needed and increases accuracy and brass life considerably. Second, if the fired case is a tight fit on a bullet or the bullet won't enter a fired case, the necks need trimming, or reaming, and you are going to build pressure.

[littlejack]

+ 1 on what flounderman said.

[B R Shooter]

As long as the brass chambers, there is no good reason to full length size it. Half to 3/4 of the neck is all that is needed and increases accuracy and brass life considerably. Second, if the fired case is a tight fit on a bullet or the bullet won't enter a fired case, the necks need trimming, or reaming, and you are going to build pressure.

So how much clearance does it take between the case neck (with bullet seated) and the chamber not to cause pressure?

What amount of pressure does it take for you to seat a bullet in the case? Is it reasonable to say it takes about the same amount of pressure to move the bullet out of the case as it took to push it in?

For sake of argument, let's say it takes 100 pounds of force to seat a bullet into a case. Do you think that added 100 pounds of force to move the bullet out makes a difference in the 40, 50, 60 THOUSAND PSI that takes place in powder burn?

This is an old wives tale. Brass has springback. IF you chamber a loaded round then remove it, and there are no marks on the case neck where it was dragging or squeezing into the chamber, there is obvioulsy clearance. Plain and simple. It will only take the same amount of pressure to push the bullet out as it did to seat it. No added constriction, no added pressure.

In benchrest, it is very common to the turn case necks (not trim) for as little as .001" TOTAL clearance in the chamber. This is done so the round is perfectly centered to the bore. There is no excessive pressure from doing so. The pressure builds, the bullet moves down the barrel the brass springs back to almost exacly where it was since it hardly moved.

Granted this is done in a controlled and deliberate manner. But if there is clearance between the loaded brass and the chamber at the case neck, there won't be a cause of increased pressure. The LENGTH of the brass if far more likely to be a cause.

[leftiye]

Anything that happens at the start of the launch has amplified effect on pressure (and everything else). Try making that initial exiting from the case a little harder by having a ding on your case mouth. Blown primer time! While .002" clearance works just fine, a little dirt can make huge differences in pressures in that scenario.

[B R Shooter]

Factory chambers are made quite generous for a couple reasons. They need to be able to shoot any brand ammo of any weight bullet, and be able to chamber a reasonably dirty case in the event a round was dropped in the field or similar. This is understood. When reloading, people have the abilty to taylor the rounds for their intended purpose. If one wants to fit the case in a given chamber they can. At the same time, if one wants to seat a bullet closer to or even touching the lands, they can. That alone many times can produce better groups than following the "listed" COL. That's why we reload. Can having a bullet very close to or touching the lands cause an increase in pressure? Slightly perhaps. But I firmly believe that if you have an over pressure round simply by seating the bullet to touch the lands, you are already over the reasonable limit. With some factory chambers and military chambers, then throw in the tolerances of mass production, it's a wonder some rounds even go off.

[leebuilder]

Been reading alot. Talked to another silverback. I believe, and what i have done in the past, with pressue signs back off or go to another powder. Plus 1 with generous clearances and use of peowned barrels, and factory ammo (some of that eastern european stuff is HAWT). Pressure increases with tempurature too. One silverback talked at lenght about primer material and form, leading to false assumptions. We all agreed the brass flowing into extractor cuts is bad and shall be avoided/prevented.
Be safe

[littlejack]

One other thing that has been identified as a false pressure sign, but not mentioned, is a burr around the extractor groove or the plunger hole.
These will leave a bright mark on the face of the case, but no over pressure really exists.

[Larry Gibson]

littlejack

I have some experience pressure testing the 7.62x54R in my SAKO Finn M39. I have tested 8 hand loads, 2 commercial loads and 9 milsurp loads. Keep in mind C.I.P. standards for the 7.62x54R give a PMAP of 46,000 psi (transducer). Both commercial loads (Winchester and Norma) I tested in my M39 using the Oehler M43 produced very close to 46,000 psi(M43). The milsurp loads produced from 39,000 - 45,000 psi(M43). My hand loads duplicating milsurp "L" and "D" ammunition using 150, 174 and 180 gr .311/.312 jacketed bullets produced 39,800 - 46,500 psi(M43). Cast bullet loads using 29 gr 4895 under the 311299 and 311291 produced 22,800 and 26,200 psi(M43).


I do not know what level of psi a MN will handle before letting go because I have not and do not intend to find out. Thus using fired primer condition as an indicator of psi is indeed "sketchy at best" considering the lower levels of psi the MN was apparently made for. By the time you get into the realm of the brass flowing into the ejector slot the psi is way, way above that intended for the MN. Some specific information regarding your exact loads (how much 4064 and neck clearance in the chamber neck?) may provide useful further information?

Larry Gibson

[littlejack]

Hey fellas:
Went out of town yesterday, just got back.
Hey Larry, glad you chimed in. I wasn't going to intentionally load till the brass flowed into the cracks, was just getting information for my mental archives.
I went out and got some chamber dimensions from a impact cast that I done a few years back.
First off, I measured one of my loaded cases at the neck, with a .312 bullet seated. Diameter is .330. The impact cast dimension at the same point is .341. That is generously over sized for that area.
Next, I measured the extended length of the chambering in the neck. I was approximately .150 longer than the case neck itself.
Next, I measured the length of the taper from the end of the neck length + .150 to the starting of the bore and grooves. It measured approximately .100 in length.
Next, I measured the cross diameter of the starting of the grooves. That was .318. Then .540 down the bore it measured .315. The .540 was the length to the end of the impact cast.
Case head dimension of the impact cast, .486 (.200 up from the base of the case according to to my Hornaday book)
Shoulder diameter of the impact case is .463.
So, this particular chamber has very generous dimensions. The diameter of the neck area and the starting of the bore/groove area leaves plenty of tolerance for gas blow by. I am quite amazed at the accuracy this rifle is shooting with the bore/groove dimensions it has. I used my Mitutoyo calipers to measure these dimensions. They were so generous, I don't think mics would make any difference. My calipers measure to within .001.
The loads I tested were with 46 and 47 grains of IMR 4064 under a 200 grain bullet. I did start lower, then worked up to that.

Nise, now I understand. As you can see, the chamber neck area in my rifle must be a lot longer that yours.

[Larry Gibson]

littlejack

The loads I tested were with 46 and 47 grains of IMR 4064 under a 200 grain bullet. I did start lower, then worked up to that.

That load would be about right for duplicating the "D" ball ammunition with 174 or 180 gr bullets. Might be a bit stiff with 200 gr bullets. What 200 gr jacketed bullets are you using?

Are you FL sizing the cases? If so are you headspacing on the rim or the adjusting the dies to headspace off the shoulder?

Larry Gibson

[Cap'n Morgan]

I sometimes have used case head expansion as a poor man's pressure gauge: http://shootersnotes.com/articles/when-are-pressures-too-high/ Done correctly it is a safe and reliable method, but I would not recommend it for anything but modern high pressure cartridges.

[1johnlb]

For those that are unsure of the Mosin's strength. Here's one shot with a full case of 2400, although I don't recommend trying it yourself.

Mosin Nagant Torture Test: Part 1 - YouTube


www.youtube.com/watch?v=gfiXFyIbOZw (http://www.youtube.com/watch?v=gfiXFyIbOZw)

Be sure not to miss part 2

https://www.google.com/url?sa=t&source=web&rct=j&ei=aGoYVdXSD4-XyASx_IKoCA&url=http://www.youtube.com/watch%3Fv%3D2Bzls73WH7w&ved=0CCQQtwIwAQ&usg=AFQjCNEnLa9ei_18hUmMogabCUTgoa1_MA&sig2=-3y1QmasF_D_Nu5hV9LnLQ


Here's a case head of a 308 shot with what I believe was a double charge of 2400 in a Savage 110



135386
135387

[Larry Gibson]

Interesting. Yup, strong actions. The use of steel only cases, even with their reloads, certainly helped. Would it have been different with brass cases? Probably. I, however, prefer not to have to beat the bolt open. Much easier if I stay with in the operational parameters of the cartridge and rifle. I don't envision needing more than 3190 fps with a Hornady 123 gr jacketed bullet, 2900+ fps with a 150 gr jacketed bullet or 2700 fps with a 174 - 180 gr bullets bullet in either my Russian M28/30 sniper or my Finn M39. That can be done by staying under 46,000 psi and those loads don't lock up the bolt.

Larry Gibson

[littlejack]

Larry:
The bullets that I have been testing lately are of unknown make. I looked to find a example of them on the net, but nothing was posted. They are a 200 grain jacketed 8mm bullet with a round nose and flat point. I bought these from another member here on the forum a couple years ago. They did not shoot well in my 8mm-06 AI, so I sized them to .3127. They shoot exceptionally good in my Mosin. The slugged diameter of my Mosin is .313. These particular bullets have a crimp groove, and, what looks to be a shallow square groove to lessen friction/pressure. I really don't know.
In the beginning, I was neck sizing. Then I switched to partial sizing. Now, I use a .080 washer under the sizing die that is set to partial size. When the case gets hard to chamber, I just remove the washer and partial size one time. Then, replace the washer and repeat the sequence.

1johnlb:
That is oner impressive Torture Test.
I looked in my P.O. Ackley book the other day to see if he had tried to blow a Mosin. I did not find any section where
he did. His other tests
with the other military rifles was quite impressive and very informative. Very surprising that the Japanese rifles held
up to, and as good as most, and better than some of the other rifles.
There was also a test done where they took an 30-06 chambered barrel, reamed the neck to take a 8mm bullet,
loaded and fired it down the 30-06 barrel. The results were that the pressure did not spike as they thought it would,
and every thing stayed intact. They did say, (I don't think most people realize) that the bullet is sized down as soon
as it 's whole length is in the bore. Then, pressure would drop.
Jack

[Patrick56]

They tried to blow up the MN in Finland and they were not able to do it. The only result was a bolt that could not be opened. Headspace is a common issue with the MN. As an young conscript gunsmith, we checked the headspace by simply using a no go and a go gauges and a big box of bolt lugs. If you hold the MN bolt removed from the rifle with the safety towards you, turn the safety one click clockwise and you can remove the lugs without releasing the striker spring tension.

[Larry Gibson]

littlejack

Sounds like you've a good handle on case sizing. I'd venture your 4046 load is pushing well into the high 50K psi range which is perhaps where the pressure signs are coming from.

Many of us could have told the guys doing the destruction test the bolt would not come back out of the receiver. There is too much steel in the large rib on the bolt. Almost always the MN fails with a burst barrel (as the older dude thought would happen) or the bolt head (locking lugs) lock up solidly. Once the bolt head locks up solidly the action is toast as the lugs have set back the locking surfaces. Too bad they didn't try a bore obstruction with a standard service "L" load, that's how we destroyed a MN (intentionally btw) and the bolt body still was in place in the receiver.

Larry Gibson

[littlejack]

Larry, thank you for your testing results, it was interesting, and very informative. Also, thank you to all the other members that posted on this thread that had information to share.
Jack