What would you have told him ?

[Ben]

My friend had me look at these primers on some 30-06 cases.
He said he shot 56.0 grs. of IMR - 4831 with a 180 gr. jacketed in 30-06 brass.

I gave him my opinion about the appearance of the primers, what is yours ?

http://i1155.photobucket.com/albums/p545/Ben35049/IMG_1968_zps4qg7hqre.jpg (http://s1155.photobucket.com/user/Ben35049/media/IMG_1968_zps4qg7hqre.jpg.html)

[SSGOldfart]

Back off that load was a little to hot and/or check his powder measurer see if it throwing the right charge

[303Guy]

Interesting that the primer edge hasn't flattened out. I have seen primers like that from factory loads. Eastern block or Chinese. There was no sign of excess pressure, just the indent bulged back out like in the photo.

[William Yanda]

That ring around the firing pin indent looks like the pressure is pushing the primer back into the bolt. Too much pressure.

[Ben]

This is interesting, keep your replies coming...............Here is what the Speer loading manual says about his charge of 56.0 grs. of IMR 4831.

180 Speer RNSP, Spitz BTSP, Spitz SP, MT SP or GS SP IMR IMR-4831 55.0 2544
Remarks: start charge

180 Speer RNSP, Spitz BTSP, Spitz SP, MT SP or GS SP IMR IMR-4831 59.0 2684
Remarks: max charge; compressed load

[oneokie]

Overly large firing pin hole in the bolt. Or soft primer cups.

[longbow]

Yes, I noticed the same thing. Any time I have reached somewhat high pressure the primer flattens out noticeably. These have what appear to be nice round edges.

Without looking up the load data I have no idea if it is too heavy a powder charge but I would say yes with primer dents extruding back into the bolt after the firing pin. Odd that they didn't flatten more though.

Primer make?

Longbow

[ubetcha]

Overly large firing pin hole in the bolt. Or soft primer cups.

My thoughts also. The edges of the primers do not look flattened due to over pressure.

[44man]

Weak Pin spring. Primer pressure is pushing the firing pin back.

[MtGun44]

Bolt hole for firing pin is oversized, most likely. I would have to compare to factory
ammo to be certain, but seems extremely unlikely that there is a pressure issue due
to the nice, rounded edges on the primers.

Bill

[jonp]

Odd that it didn't flatten. I agree with other comments. I think the primers are soft. I'd still back off the powder a grain or two and compare. I had something like this with pistol primers not long ago. Well under max but enough of a crater that the cylinder would not turn

[runfiverun]

The primers flowed into the bushing area around the firing pin.
Shrug

[dubber123]

Overly large firing pin hole in the bolt. Or soft primer cups.

I give Nolan the gold star. No flattened edges, either small pin tip or too large of a firing pin hole.

[KYCaster]

Hodgdon site says 180 gr. Sierra SPBT.......56.8 gr. IMR4831 is max.

Looks like too much room around the firing pin......needs a bushing.

Looks like location of the firing pin strike is inconsistent....some centered, some not. Sloppy chamber?

Not a very deep firing pin hit....short firing pin or VERY SOFT primer?

More details on the gun and load?

Jerry

[Lefty bullseye shooter]

In my experience first sign of pressure is flattened primer THEN more pressure is flattened primer and crater around firing pin indent. With signs of high pressure the crater is very sharp edged not rounded like the picture. I would go with oversized firing pin hole also.

Scott

[bhn22]

Weak Pin spring. Primer pressure is pushing the firing pin back.

Me too! I'd also check the firing pin hole & pin protrusion, just to be thorough.

[sirgknight]

Algebra problem with visual results....first of all I looked up the load data at Hodgdon for the 180gr bullet over IMR4831. It shows max load at 56.8gr, compressed. The primers, to me, indicate that he is "right there".

[Ben]

Truth is other reloads that were safe gave the same primer appearance. Rifle is an old ( Mid 70's ) Remington Model 760, pump, 30-06.

I told my friend that the firing pin hole was too large.

He said the loads were accurate, they ejected well from the rifle.

I told him he might try a different primer. The primers might be a bit soft ? Yes, he might drop 1 - 2 grs. of propellant, but the edges of the primers don't seem to indicate high pressure ? ?

Ben

[wv109323]

I would examine the primers and the rifle bolt. Something strange is going on. The bottom most cartridge has a larger diameter raised portion than the others. It also appears that some of the primer strikes are off center more than others.
I would try another brand primer with the same load.

[castalott]

Alright, I'll make a fool of myself....2 of the primer strikes are centered and 2 are way off. That is a really big chamber or some strange brass. Decap them and see if the primer holes are drilled out a little. I've read about something like this with auto loading rifles where the firing pin floats back and forth in the ejection cycle to strike the primer twice. So I'm guessing very soft primers in an autoloader where the firing pin impacts the hammer....YMMV...lol PS... were the cases sooty? Like the powder wasn't burning right? Ok..I admit it...I don't know what I am talking about

[Yodogsandman]

Weak Pin spring. Primer pressure is pushing the firing pin back.
I agree.

Ben, what a great idea for a thread!

[SSGOldfart]

Maybe head space is off just a little?or OAL to short causing arise in pressure
Speer also says to reduce by10% to start to.was there any other signs of high pressure?
Speer#10 says 58.5 is max for IMR4831 starting load is 54.5

[fatelk]

That does not look like a hot load at all, to me. Clearly the primer is flowing back into the firing pin hole for some reason, either due to a weak spring of enlarged hole as others have said. I'd be inclined to agree with 44man if I had to guess, but I'm certainly not an expert.

I've used that same load before in a 30-06, or really close to it. In my rifle with my components it was not at all a hot load.

[mattw]

Oversized firing pin hole or soft primers. Try CCI primers and see what that does. My 03 does that with Winchester primers.

[jonp]

Truth is other reloads that were safe gave the same primer appearance. Rifle is an old ( Mid 70's ) Remington Model 760, pump, 30-06.

I told my friend that the firing pin hole was too large.

He said the loads were accurate, they ejected well from the rifle.

I told him he might try a different primer. The primers might be a bit soft ? Yes, he might drop 1 - 2 grs. of propellant, but the edges of the primers don't seem to indicate high pressure ? ?

Ben

More info yields the answer.

[Blackwater]

It is definitely NOT a hot load. That particular kind of cratering isn't caused by pressure, and the most likely cause is as 44man said, weak firing pin spring. However, I've seen this before and in that case, the sizer die had been screwed in a little too far into the press, shortening the base to shoulder length. This increased headspace just enough so that the setback caused the little dimpling around the firing pin indention. Readjusting the die a partial turn higher, and then backing it down in increments just so the sized case would chamber properly with only a bit of "feel" as the bolt was closed eliminated this for the owner. FWIW.

[Ben]

Alright, I'll make a fool of myself....2 of the primer strikes are centered and 2 are way off. That is a really big chamber or some strange brass. Decap them and see if the primer holes are drilled out a little. I've read about something like this with auto loading rifles where the firing pin floats back and forth in the ejection cycle to strike the primer twice. So I'm guessing very soft primers in an autoloader where the firing pin impacts the hammer....YMMV...lol PS... were the cases sooty? Like the powder wasn't burning right? Ok..I admit it...I don't know what I am talking about

Great theory, but a Remington Model 760 isn't an autoloader, it is a pump.

Ben

[lolbell]

I'm gonna say too large pin hole and Federal Large Rifle primers.

[Ben]

I agree.

Ben, what a great idea for a thread!

Yes, I thought that I'd " Test the Waters " with this one to see what everyone thought ? ?

Ben

[Alan in Vermont]

Bolt hole for firing pin is oversized, most likely. I would have to compare to factory
ammo to be certain, but seems extremely unlikely that there is a pressure issue due
to the nice, rounded edges on the primers.

Bill

+1 Saved me from typing the same thing.

[Ben]

Bolt hole for firing pin is oversized, most likely. I would have to compare to factory
ammo to be certain, but seems extremely unlikely that there is a pressure issue due
to the nice, rounded edges on the primers.

Bill

I'm with you Bill, if this is a high pressure issue, why are the edges of the primers still rounded ? It isn't about high pressure.

Ben

[Eutectic]

I believe those Rem 760's have an inertia firing pin.... In other words, it is too short to reach the primer. When the hammer hits the firing pin it is 'thrown' forward with inertia to reach and fire the primer. The Colt 1911 is the same way.

Sometimes with certain primers, time pressure curves, etc, you will get fired primers that appear as shown. It is flowing into the firing pin hole some in the breech bolt and is not a high pressure sign.

WW2 EC ordinance steel case .45 Auto rounds had a copper primer. I have seen these flow the indentation back so flush the primer almost looked un-fired!

Eutectic

[ballistim]

Weak Pin spring. Primer pressure is pushing the firing pin back.

Recently bought a tang safety Ruger M77 and had a very similar problem, so I bought a bolt tool and replaced the stock spring with a Wolff spring at 24lbs., cleaned and lubricated the disassembled bolt and problem solved. Not saying that is the problem, but could be or part of it.

[Ben]

Might be ? ?

[Indiana shooter]

Looks like a weak firing pin spring to me. The primers are still round and there's no flowing brass on the head stamp. The pin just don't appear to be striking the primer that hard, I had this happen with an old pre-64 win 70 in an 06. My problem was solved by a thorough disassembly and cleaning of the bolt.

[bruce381]

+1 yeah

Oversized firing pin hole or soft primers.

[geargnasher]

My first thought was they were fired in an M1 rifle, seen that before....but then I read that they were fired in a pump gun. I'm going with the pressure inverting the primer dent, driving the firing pin back into the bolt (making a teat on the primer) and making the hammer bounce back and then light strike again, forming the small dent. There's probably some excessive clearance around the firing pin, possibly from blown primers or corrosion in the past. First thing I'd check is the bolt face.

Like others, I see no signs of excessive pressure.

One time I picked up a handfull of .44 Magnum brass at the range that had obviously been reloaded (light sizing die scratches and nickel primers in Winchester cases), and found just ONE case that had an alarmingly flattened primer. I studied it a bit, thinking extremely excessive pressure, then noticed the rim was exceptionally thin. I measured it, even rechambered the fired case in one of my own revolvers, and noted the excessive "headspace". My conclusion was that the primer popped almost halfway back out of the case when it was ignited (after the hammer had driven primer and case fully forward in the chamber), then the case stretched back to the breech face under normal pressure, flattening the primer in the process.

Gear

[Ben]

Gear,

Isn't it amazing what you can pick up at the range.
I've always said that it was a great testimony to the firearms industry that some of what I've seen didn't have body parts and/or any blood near the location of the brass that I picked up.

[Ben]

"Stop. Something is wrong. That's not a normal fired primer shape."

Fine, what do you say is causing it ? ?

[454PB]

I vote for a weak firing pin spring. I had the same symptoms with my Mossberg .308 to the point that it would actually blow out the pin hole in the primer. I added a washer in the bolt to increase the spring tension and all the problems went away.

[Maineboy]

Thanks for the post; I find this interesting. My guess is the pressure is normal but the firing pin hole is enlarged. I certainly would like to examine the rifle.

[dubber123]

The 760 I worked with didn't have a whole lot of extracting force, and it was pretty easy to tell when pressures were too high. I had to stop well short of book max, but only due to extraction issues. I think that load is just fine in your friends gun. If the pin hole is too big, make a bigger pin. Actually, it's not hurting anything the way it is, I wouldn't let it worry me much.

[btroj]

Large firing pin hole. Not a big deal.

[fast ronnie]

Federal primers? Could be combined with oversized firing pin hole. Is it bigger than .075 or so? Even that might be a bit much, especially with and undersized pin. Combined with a headspace issue. Is there any residual lube left on the cases? Was the chamber clean, with no oil or lube? If headspace is wrong (case could be too short, you will get primers backing out, then pushed back in, especially with lube in the chamber. The brass should be grabbing to the chamber walls from pressure while case is pressurized.

[aspangler]

Large firing pin hole and could the primers be large pistol instead of large rifle. I have seen that mistake before and saw similar results.

[Mk42gunner]

I'll go with the weak firing pin hit theory. As I recall the inner workings of a 760 your friend will most likely need a new hammer (main) spring.

Robert

[Gtek]

Here are my thoughts. We could remove and disassemble bolt and confirm exact firing pin hole ID vs. pin OD, step one. Next I would think that the firing pin indentation is probably/could be ok at time of ignition, but does the dimple look small? The case is pushing primer out enough and flowing into bolt face and into pin hole? Due to possibly over sized and or polished chamber with light loads not allowing case grab at time of ignition. Enough pressure for anvil to take thrust through case and push center but not enough to flatten edges. Open action and put untouched factory round in chamber and see if it rattles around, then measure against fired cases. Small base sizing? Interesting-----

[leebuilder]

Nice. But you are pushing the limit. I use this round. H4831 one of the best powders around. Not flattened so no cause for alarm.

[.30-06 fan]

With my limited knowledge i would of said, "stop that does not look right".

[Frank46]

I'm of the opinion that weak firing pin spring, oversized firing pin hole. Are the two main causes. Primer edges are rounded all the way around and does not look like a high pressure load. Easy fix, bush the firing pin hole. Or getting another bolt and headspace it to the rifle. Frank

[KLR]

Check to see if it has a chamfered firing pin hole. My 7600 does and it does the same thing. It's worse when shooting mildish loads and when it gets dirty.

[leadman]

I had a couple of the Remington pumps and autoloaders and an off center firing pin strike is not unusual on full length sized brass. The chambers tend toward the large size on these. I do agree that the firing pin and hole in the bolt should be looked at.
I have used that same load in my Savage 110DL and it was fine with case expansion less than some factory loads.

[oscarflytyer]

Read thru about half the posts. Took that long to see what I think it might be - excessive headspace. Never seen it, but pix don't look like what is usually high pressure load. And excessive headspace could be due to two or three things.

[Motor]

Great theory, but a Remington Model 760 isn't an autoloader, it is a pump.

Ben

This is true the 760 is a pump action rifle BUT it also has a free floating firing pin. Have your friend briskly chamber a round then examine the unfired primer. It will have a very light mark on it where the firing pin hit from inertia. Just like you see from an unfired round removed from an AR-15.

All the week firing pin comments are wrong too. The rifle has a hammer. If its going off its not week.

The primers are simply flowing back into the firing pin bore. It very likely has a chamfer on it.

Motor

[lightman]

I'm not seeing any signs that I would call high pressure. The primer is not flat or flowing into the edges of the primer pocket and there looks to be no brass flowing into the ejector or extractor holes in the bolt. What I am seeing is a cratered primer from a sloppy firing pin/bolt fit. The main problem with cratered primers is the small pieces can work their way into the firing pin raceway and down into the trigger.

[10x]

Oversized firing pin hole or soft primers. Try CCI primers and see what that does. My 03 does that with Winchester primers.

This ^^^^^

Change brands of primers to CCI if you can find any and start to work up from minimum again.

[Hamish]

Friends don't let friends shoot mixed head stamps,,,,,,,,:bigsmyl2:

[mallard1]

After resizing brass, are the cases trimmed to the correct length. This could cause the cases to be pushed back into the bolt causing the primer indentation. Just another idea of what could have happened.

[Ballistics in Scotland]

Interesting that the primer edge hasn't flattened out. I have seen primers like that from factory loads. Eastern block or Chinese. There was no sign of excess pressure, just the indent bulged back out like in the photo.

Yes exactly. There are no signs of toolmarks on the bolt face either, although of course a bolt-face can be made smooth. He should consider carefully whether he is using excessive charges or bullet weight (he probably knows, but I think the problem is just as likely to be something else, or partly something else.

This could be poor firing-pin fit in its hole, a substituted or shortened mainspring, a lightened or titanium firing-pin installed without a stronger spring, and probably one or two things I haven't thought of. An oversize hole and pin, both, wouldn't have caused this if it had been in moderation. I would slightly enlarge a hole which had become bell-mouthed (probably need a carbide reamer), as long as I could get or make a pin to closely fit it.

This picture shows what was done by someone who knew what he was doing, developing an Improved version of the .244 H&H Magnum, just in case anyone needed one. Note that this one does show toolmarks on the primer, and an indentation into the ejector cut. It also shows that his rifle, unlike the OP's, held the firing-pin very close to its furthest forward position while all this was going on.

Against all probability he did achieve excellent accuracy with safe vital signs and even higher velocity than the original. But he had slower powders than H&H did.

[Eutectic]

The inertia firing pin (some call free floating) follows different rules. A stronger firing pin spring will show signs as shown more so than a weaker one. The fallen hammer has NO influence on this as the firing pin is shorter than the breech bolt's length. (unless the 'extrusion' becomes so great as to take up firing pin length clearance)

I think the longer time pressure curve (from the 4831 powder) is the culprit. Tight case fit (headspace) will aggravate what you are seeing.
Some cases fired with faster powder or even factory loads in the same gun would tell us a lot!.

Eutectic

[44man]

Firing pin hole has to be checked too.
There is a lot of pressure inside the primer cup. A revolver can have the hammer blown back to almost full cock with still a good indent showing in the primer. We took pictures of this happening before recoil started. We found double pin strikes on S&W revolvers, some outside the primer on the brass. This is why some .500's doubled, the hammer bounced back, cylinder unlocks and turns backwards and if there is a live round there the hammer will fire it.
If the pin is blown back, the cup will try to flow into the hole.
Bolt guns need a very strong mainspring for top accuracy. The worst thing to do with any gun is to reduce the hammer or mainspring, looking for a lighter pull.

[Ballistics in Scotland]

The inertia firing pin (some call free floating) follows different rules. A stronger firing pin spring will show signs as shown more so than a weaker one. The fallen hammer has NO influence on this as the firing pin is shorter than the breech bolt's length. (unless the 'extrusion' becomes so great as to take up firing pin length clearance)

I think the longer time pressure curve (from the 4831 powder) is the culprit. Tight case fit (headspace) will aggravate what you are seeing.
Some cases fired with faster powder or even factory loads in the same gun would tell us a lot!.

Eutectic

I have never liked the idea of an inertial firing-pin in a high-pressure firearm. A return spring in front of it should indeed be as weak as will do the job, and I would feel happier with the system seen on some falling-blocks, whereby operating the lever cams the firing-pin out of the primer. I suppose dirt in the firing-pin channel or a deformed return spring might produce the OP's problem.

But the faster the hammer, the faster it makes the firing-pin move, and the more inertia it has.

[44man]

The firing pin on the 760 and 740 do not have pin springs but are NOT inertia pins. There is no gap at the back of the pin when the hammer is against it. Yet the pin will blow back and take the hammer back from internal pressure. That leaves a hole for the cup to flow into. The pin on these rifles should be long enough to keep the hole blocked unless the hole is large.
When the pin is pulled all the way back, it should be flush with the bolt face.
The reason a 740 will not slam fire is because the pin does not get a running start, unlike an SKS that will with a thin primer cup. I have turned SKS and AK pins for a spring and stopped slam fires with our primers.

[upnorthwis]

Some chrono data would be nice. If it was only going 2100 fps you could eliminate high pressure as a cause and look for something else.

[41 mag fan]

I've got a Remington model 700 Boon and Crockett in 300 win mag that has the same problems. Interesting read on this

[Ballistics in Scotland]

Some chrono data would be nice. If it was only going 2100 fps you could eliminate high pressure as a cause and look for something else.

True if it was really the load described, but it is possible to get low velocity with a load giving excessive peak pressure, if you really work at it with some determination.

I have "The NRA Gunsmithing Updated", which is mostly a very valuable book, as long as you don't expect it to be updated anywhere near the pressure. Unfortunately the price nowadays on www.bookfinder.com (http://www.bookfinder.com), both new and used, make me wince. But there is one article by a US service pistol team member, which more or less takes the unusual tack, for that book, of advising the amateur to do no gunsmithing whatsoever. He does say, I remember, that it is very useful for the reloader to recognize the different powders by appearance. A good many other people advise us never to have to.

[robg]

measure case head and compare to unfired case , primers are not an accurate indicator of pressure,

[TXGunNut]

Overly large firing pin hole in the bolt. Or soft primer cups.


My thoughts exactly. Sometimes primers lie, other times they're just misunderstood.

[Motor]

The firing pin on the 760 and 740 do not have pin springs but are NOT inertia pins. There is no gap at the back of the pin when the hammer is against it. Yet the pin will blow back and take the hammer back from internal pressure. That leaves a hole for the cup to flow into. The pin on these rifles should be long enough to keep the hole blocked unless the hole is large.
When the pin is pulled all the way back, it should be flush with the bolt face.
The reason a 740 will not slam fire is because the pin does not get a running start, unlike an SKS that will with a thin primer cup. I have turned SKS and AK pins for a spring and stopped slam fires with our primers.

This is correct. It DOES NOT have a inertia firing pin. It simply free floats. The hammer very likely bounces back a little from recoil as well.

IMHO: Everything looks fairly normal for this type of rifle. Yeah the firing pin hole is chamfered or maybe even worn a little. Its really NBD.

Guys really need to read the thread. This is a Remington 760 PUMP ACTION RIFLE. Not a bolt action. In fact its almost identical to the self loading 740 series except you pump it instead of it pumping itself like the semi's do.

Why is this thread in the "Cast Boolit" forum?

"He said he shot 56.0 grs. of IMR - 4831 with a 180 gr. jacketed in 30-06 brass."

[Eutectic]

The firing pin on the 760 and 740 do not have pin springs but are NOT inertia pins. There is no gap at the back of the pin when the hammer is against it. Yet the pin will blow back and take the hammer back from internal pressure. That leaves a hole for the cup to flow into. The pin on these rifles should be long enough to keep the hole blocked unless the hole is large.


I believe you are correct 44man..... I say it this way as I didn't have a 760 to look at but I do have a 7600 .35 Whelen. It indeed has a spring loaded firing pin of a rather unique design with twin sleeves that prevent the pin from going forward until the bolt is closed. Then there is enough clearance for the pin to reach the primer. I wouldn't call it a 'floating' firing pin either.

The hammer is very light in mass and the firing pin has every mechanical advantage to 'push' the hammer back (as compared to a bolt gun). So that could indeed be happening.?

My comments about firing pin spring pressure and pin touching the hammer are also incorrect if the 760 and 7600 are designed the same way.

My 7600 Whelen mentioned doesn't display this primer 'flow' as Ben's picture. It does however, crater primers quite easily as maximum loads are approached. Loads at similar pressures in my bolt gun or even my Ruger #1 .35 Whelen do not crater at these pressures. I'm talking 'crater' here with a sharp edged corner... not primer 'flow' as Ben's example.

Sorry for the bum steer guys.... Guess I just looked at too many Remington 870's!

Eutectic

[Motor]

I believe you are correct 44man..... I say it this way as I didn't have a 760 to look at but I do have a 7600 .35 Whelen. It indeed has a spring loaded firing pin of a rather unique design with twin sleeves that prevent the pin from going forward until the bolt is closed. Then there is enough clearance for the pin to reach the primer. I wouldn't call it a 'floating' firing pin either.

The hammer is very light in mass and the firing pin has every mechanical advantage to 'push' the hammer back (as compared to a bolt gun). So that could indeed be happening.?

My comments about firing pin spring pressure and pin touching the hammer are also incorrect if the 760 and 7600 are designed the same way.

My 7600 Whelen mentioned doesn't display this primer 'flow' as Ben's picture. It does however, crater primers quite easily as maximum loads are approached. Loads at similar pressures in my bolt gun or even my Ruger #1 .35 Whelen do not crater at these pressures. I'm talking 'crater' here with a sharp edged corner... not primer 'flow' as Ben's example.

Sorry for the bum steer guys.... Guess I just looked at too many Remington 870's!

Eutectic

Not really but they are close. The 7600 is updated and improved. Go to gunpartscorp.com and study the Schematic (s) of both rifles.

The 760 does not have the spring on the firing pin. It will dimple primers when briskly loaded.

Motor

[Hickok]

I've got a Remington model 700 Boon and Crockett in 300 win mag that has the same problems. Interesting read on this
I know this doesn't pertain to the Remington Pump that is being discussed.

Remington has purposely beveled the firing pin hole on their Model 700 rifles for last few years, "supposedly" it is an added safety measure in that it makes the primer less likely to pierce, because the bevel creates a thicker radius when the firing pin strikes and the cartridge is fired.


NOW, I agree this just doesn't make sense, but that is what Remington is saying. I have two newer Model 700's in .308 caliber, one is the 26" heavy barrel, and the other standard weight 24 barrel, and both give the same primer protrusion. In fact, you can remove the bolt from either rifle and see the bevel/chamfer around the firing-pin hole.


I have several other older Model 700's and they do not have this bevel/chamfer around the firing pin hole. I don't like it, but I just don't let it bother me, as it does no harm, but it does go against my way of thinking.


As to the OP's rifle, I agree that firing pin hole may be large, or hammer spring may be weak, allowing firing pin to push backwards on firing.

[Hickok]

130752 Bevel/chamfer on 700 Remington Bolt.

Forgive me Ben for thread drift, just wanted to help 41 mag fan.

[Smoke4320]

Overly large firing pin hole in the bolt. Or soft primer cups.

I agree .. may also be a combo of large pin hole/soft primers and slightly overcharge for YOUR gun
That would explain why the primer edges are not flat .. classic sign of overcharge

[41 mag fan]

Hmmmm... I'm going to have to take a look at it and see. .. this rifles between 6 to 8 yrs old iirc.... Thanks Hickok... I'll see what it looks like. ..I've not worried about it as it has not showed issues of over pressure. ..

[Hickok]

41 mag fan, no it is nothing to worry about, as Remington is deliberately doing this. I just go on shooting my newer Remington's too, but I hate the look of the primers! Too me, it is a fix for a problem that doesn't exist.

[EMC45]

Overly large firing pin hole in the bolt. Or soft primer cups.


Beat me to it!

[Pilgrim]

That .244 load is beyond max. in that rifle (post #59)! The firing pin shows definite cratering, the primer edges are flatter than normal, PLUS you can see the ejector hole on the case head. That load is probably in the 70kpsi range if not a bit higher.

[BrianL]

It looks mechanical to me. Worn out firing pin hole? I had a similar looking condition once with a long firing pin thinning the brass so that it flowed backward. I actually had several pierce.

[Eddie2002]

I'm betting on soft primer cups, maybe he used large pistol instead of rifle primers and an oversized firing pin hole which caused the dimpled pimple.
Haven't see anything like that with my BDL 700 in 30-06 but the rifle was built back in the 80's not recently.

[retvet09]

My bet is the headspace is gone. The firing pin is pushing the case further into the chamber until it bottoms out on the shoulder. Still having enough contact with the bolt and firing pin protrusion to ignite the primers. This causing the shallow firing pin strikes and the case and primer to slam violently back into the bolt face. This will cause what appears to be primer cup flow. When it it really just the force pushing the firing pin back. This force most but not all the time will result in primers to have rounded edges. This is because the primer is being pushed out of the case and against the bolt face first then reseated as the case comes back.

If you want to know for sure check a fired case against a unified case for headspace differences. My bet is this rifle will exhibit large amounts of case stretch from trying to make headspace.

[GaryN]

Bolt hole for firing pin is oversized, most likely. I would have to compare to factory
ammo to be certain, but seems extremely unlikely that there is a pressure issue due
to the nice, rounded edges on the primers.

Bill

This is what I think too. Mtgun44 just says it better than me.

[Ballistics in Scotland]

That .244 load is beyond max. in that rifle (post #59)! The firing pin shows definite cratering, the primer edges are flatter than normal, PLUS you can see the ejector hole on the case head. That load is probably in the 70kpsi range if not a bit higher.

It was far beyond some loads that are beyond max, and excusable only as part of a development program which didn't involve holding the rifle by hand.

While the pistol primer and excessive headspace theories are interesting, I think both of them would show up in other ways. The primer would back out with excessive headspace, and even if the case moved back around the primer after that, I think we would see more deformation around the edges. This would surely apply also with pistol primers.

[Shiloh]

The primers are not flattened, so it doesn't look like high pressure. It appears that the hole for the firing pin to protrude through, is oversized.

Shiloh

[curiousgeorge]

I promise that I have not looked at any of the other answers, so I may be repeating what has been said and said but here goes.

Firing pin hole looks to be too large. The primers are still rounded on the outside edge which leads me to believe that the load is not over pressure.

Now I am going back to read the other responses and see how stupid I probably am.

Steve

[geargnasher]

I maintain oversized firing pin hole and the firing pin and middle of the primer cup blowing back into the recess, re-loading the hammer/hammerspring slightly thus creating the small dimple from the impact of the second, lighter bounce.

Gear

[Bullwolf]

The Colt 1911 is the same way.

Sometimes with certain primers, time pressure curves, etc, you will get fired primers that appear as shown. It is flowing into the firing pin hole some in the breech bolt and is not a high pressure sign.

WW2 EC ordinance steel case .45 Auto rounds had a copper primer. I have seen these flow the indentation back so flush the primer almost looked un-fired!

Eutectic

Those EC ordinance steel case 45 Auto rounds with a copper primer really flow!

I took a picture of a few I cleaned, and uploaded here on Cast Boolits.

http://castboolits.gunloads.com/attachment.php?attachmentid=67530&d=1366008636

http://castboolits.gunloads.com/attachment.php?attachmentid=67531&d=1366008637


I'll just echo what others have said. The load doesn't look to be all that hot. Soft primers, oversize firing pin hole, the edges are rounded still and not flat.



- Bullwolf

[Eutectic]

Pondering this whole family of Remington guns with this similar design; also remembering for many years that primers fired in them had a 'different' appearance.. (to be nice)

There is a design problem that aggravates 'primer flow' in the whole family! I am speaking of the 740, 742, and 7400 semi-autos and the 760 and 7600 pumps. So I studied the schematics for ALL of them. As to firing pin design they are pretty similar with the 7400 and 7600 having some changes. The 760 is the only one in the family that doesn't have a firing pin spring.

The trigger groups appear almost the same visually. The hammers as well. The hammer is thin, barely over 1/8" thick it appears. Hence very light in weight. Judging by my 7600, the hammer contacts the firing pin very much at the top of the hammer.

So here's what I think can happen as this post relates to. A particular primer cup configuration, too soft, or a very slow powder..... some condition, can push the firing pin back.... By design of these guns, there is very little resistance mechanically to stop this.
The internal pressure at firing pushes against the firing pin tip and pushes it back. In this case judging by Ben's fired cases, far enough THAT THE RADIUS OF THE TIP GOES BACK INTO THE HOLE IN THE BREECH BOLT. The firing pin hole DOESN'T HAVE TO BE OVERSIZE for this condition to happen. The radius area of the firing pin tip back inside the hole is all it takes. Look again how small the dimples are on the fired cases in the first post.

Eutectic

[Ben]

Eutectic

This makes as much sense as anything I've read so far.

Many thanks,
Ben

[Motor]

Ive been reloading (and hording brass) since 1985. I've seen everything you could imagine from picking up range brass.

I could post pictures of factory loaded brass fired in perfect condition firearms and have people on here go nuts saying there is something wrong !!!!

Maybe this was the purpose of this thread to strart with, just to see the responces?

What you see in the photo is typical of the 760 Remington. End of story.

Motor

[Boogieman]

Why not fire a few factory loads and compair the primers?

[Echo]

Overly large firing pin hole in the bolt. Or soft primer cups.

Plus 1. Maybe firing pin spring needs replacing...