M94 Extruded Primers

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Aaron posted this 23 March 2024

I have two IDENTICAL Cimarron Arms (Uberti) Model 94 rifles chambered in .38-55 Winchester. After filing a radius at the 6 o’clock position on the breech face, both rifles now feed ammunition without a hitch. While shooting the second rifle last week, I noticed that it simply would not open the action after the shot. It was jammed up tight.

The load is a very moderate load with Starline 2.085” (short) brass. The propellant is 28gr of IMR-3031, a Hunter Supply 260gr FP bullet, and lit off with a Winchester Large Rifle primer. This was the third such load tested in the rifle with the same result. Propellants varied on previous loads with Buffalo Rifle, RL7, A2520, and another with a propellant I can’t recall at this writing.

ALL of the loads resulted in a jammed-up action which could not be opened with normal force on the lever. To get the fired cartridge out of the chamber I had to cock the hammer and drop the hammer on the fired case. The lever could then be operated in the usual manner and the fired case extracted. Once ejected, the backed-out primers became visible. The primers are extruding at least .015” and may have been seated a tad deeper with the firing pin strike on the fired case.

A focused internet search on M94 backed out primers seemed to yield a consensus of a Headspace issue which was(is) endemic to the M94 family of rifles. Of course, there were dissenting opinions which ran the full gambit from Alien interference to dirty chambers. Rest assured, my chamber is “normal” and operating pressures are within industry standards.

I am believing the headspace argument is valid based on a few things:

  • Winchester made thicker locking bolts to accommodate headspace issues in decades past. A .005” thicker locking bolt was normal and can still be purchased on various sites.
  • When my bolt goes into battery, I can use my thumbnail to push it forward just enough to be visible. The locking bolt also appears to rise just a little bit too. That could be my imagination, but it does seem to rise a bit and hold the bolt forward.
  • The Starline .38-55 brass I have is measuring .056” rims and not the .063” as called for by SAAMI. Not as thick as they could be, but not by much.
  • My measurement for headspace is .071” or 1 thou greater than the SAAMI spec.

One thing is certain, the SAME cartridges fired in the first rifle DO NOT have extruded primers. The bolt on the first rifle can not be manipulated forward on that rifle either. Two identical rifles. One extrudes primers, one does not.

I have to say the headspace argument is correct although I have to admit, I do NOT see how excessive headspace will allow a primer to extrude. That case is going rearward when fired and should seat that primer flush, if anything, with the case head. I simply can’t envision it in my feeble little brain.

I may order a “Field” gauge to see if the action will close on it, but still have a few comparative tests to make before I spend even more money. I’ll try the 2.125” brass to see if it also extrudes primers. It could be the brass primer pocket with this lot of Winchester primers is incompatible. Like I say, a few more tests are in order.

Do any of you who shoot a M94 and have experienced extruded primers have any input here?

Rifle-1, Extruded Primers

Rifle-2, Normal Primers, Same Load

 

With rifle in hand, I confidently go forth into the darkness.

primers

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Bill*B posted this 23 March 2024

I've been told that light loads can push the primer out like a piston and push the case forward.  Pressure then develops enough for the forward part of the case to grab onto the chamber wall, but too little to push the case head back again.  If load was hotter, developing pressure would rise high enough to push the case head back, and reseat the primer. Should this be your situation, cure would be to load hotter. Just a thought.  Bill

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Aaron posted this 23 March 2024

Thanks Bill. This isn't a light load issue. Boiler pressure is normal albeit on the low side. I will however work up a stiffer load to see what happens in Rifle-1.

 

With rifle in hand, I confidently go forth into the darkness.

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pat i. posted this 23 March 2024

I don't know how well this will work with a lever gun and a rimmed case but have you tried seating the bullet out a little longer so there's a little resistance when closing the bolt and slight land marks on the bullet. It might keep the case head tight enough on the bolt face to stop the primers backing out. How does the gun shoot?

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MP1886 posted this 23 March 2024

Aaron you said "I have to say the headspace argument is correct although I have to admit, I do NOT see how excessive headspace will allow a primer to extrude. That case is going rearward when fired and should seat that primer flush, if anything, with the case head. I simply can’t envision it in my feeble little brain."

First let me tell you an expriment that Ackley did.  He removed the locking lug from a Model 94 Winchester in 30-30.  The he loades some normal pressure cartridges. He cleaned all oil, lube, wax off the cartridges. He did the same to the chamber.  He fired the rifle in a fixture and it didn't blow the action open.  The reason is the case at the moment of firing obturates to the chamber until the pressure is gone.  Ackley wanted to prove that and he did.   I feel your rifle has a little excess headspace and the case is obturating to the chamber and letting the primer blow out some.  Try this, take your same load, but lube your case up, the entire case. Don't need to touch the bullet. Then fire it and tell us if the primer is protruding. 

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Aaron posted this 23 March 2024

I don't know how well this will work with a lever gun and a rimmed case but have you tried seating the bullet out a little longer so there's a little resistance when closing the bolt and slight land marks on the bullet. It might keep the case head tight enough on the bolt face to stop the primers backing out. How does the gun shoot?

I'll add that to the list of "try this" stuff to see if I can stop the primers backing out on this rifle. OAL is a very serious issue with the M94 in 38-55 Win. Picture stuffing a cigar back into a cigar tube held horizontally. Feed angle is critical when stuffing a fat long bullet into a narrow chamber. The angle of attack is critical. Even the Starline 2.125" cases can be difficult. The 2.085" cases are better but extending the bullets out aggravate the matter substantially. The M94 in 30-30 is a no-brainer. It shoves a thin bullet into a large hole. Easy peasy there.

There is something else going on here and I am determined to find the issue. I think step one is to bring the boiler pressure up near max and see what happens.

 

With rifle in hand, I confidently go forth into the darkness.

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Aaron posted this 23 March 2024

First let me tell you an expriment that Ackley did.  He removed the locking lug from a Model 94 Winchester in 30-30.  The he loades some normal pressure cartridges. He cleaned all oil, lube, wax off the cartridges. He did the same to the chamber.  He fired the rifle in a fixture and it didn't blow the action open.  The reason is the case at the moment of firing obturates to the chamber until the pressure is gone.  Ackley wanted to prove that and he did.  

Thank you for your suggestion. Note that Ackley did his experiment with a 30-30AI cartridge, not a 30-30. Both however are bottleneck cartridges and their obturation is quite different than a straight-wall cartridge like the 38-55. That sir, is apples to oranges, so to speak. Your point however is taken. One of my pending tests will be a BP cartridge whereby the bullet really gets a kick in the arse, and the cartridge obturates on a different pressure/time curve. We shall see.

 

 

With rifle in hand, I confidently go forth into the darkness.

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pat i. posted this 23 March 2024

OAL is a very serious issue with the M94 in 38-55 Win. Picture stuffing a cigar back into a cigar tube held horizontally. Feed angle is critical when stuffing a fat long bullet into a narrow chamber. The angle of attack is critical. Even the Starline 2.125" cases can be difficult. The 2.085" cases are better but extending the bullets out aggravate the matter substantially.

 

Good point. I didn't think of that.

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MP1886 posted this 23 March 2024

First let me tell you an expriment that Ackley did.  He removed the locking lug from a Model 94 Winchester in 30-30.  The he loades some normal pressure cartridges. He cleaned all oil, lube, wax off the cartridges. He did the same to the chamber.  He fired the rifle in a fixture and it didn't blow the action open.  The reason is the case at the moment of firing obturates to the chamber until the pressure is gone.  Ackley wanted to prove that and he did.  

Thank you for your suggestion. Note that Ackley did his experiment with a 30-30AI cartridge, not a 30-30. Both however are bottleneck cartridges and their obturation is quite different than a straight-wall cartridge like the 38-55. That sir, is apples to oranges, so to speak. Your point however is taken. One of my pending tests will be a BP cartridge whereby the bullet really gets a kick in the arse, and the cartridge obturates on a different pressure/time curve. We shall see.

 

It doesn't matter the shape of the cartridge. Gas pushes on all the areas of the entire case. The neck area of the case obturates to the chamber wall just as much as the the straight wall cases. 

I would appreciate if you did oil up a case, not slopping wet, just lube it up with your fingers and shoot it. This is safe by the way as you not shooting a maximum load. Let us know what happens.

This oiling of the case or graphiting it is a method to get the entire case to blow out. So of the science to this has to do why belted magnum cases are more likely to have a head separation because non experienced reloading are setting the shoulders back by sizing them and being the belt headspaces the cartridge, when it's fires the thinner parts of the body obturate to the chamber walls and the solid rearend of the case doesn't and gets pushed back against the breech face and stretches the brass between that solid head and the obturated rest of the case eventually causing a head separationg. 

Please give it shot. 

 

 

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Wilderness posted this 23 March 2024

Aaron - if the lockup is a headspace induced issue, you may be able to prove the point by rigging some cartridges with headspace circlips as per my recent post:

https://forum.castbulletassoc.org/thread/headspacing-30-30-and-other-rimmed-bottleneck-cases/

From the rim and chamber dimensions you describe, you are looking at about .015" of slop. This is exactly the issue I was addressing when describing a way of reducing this to zero with shoulder headspacing. Of course with .38-55 you do not have  the shoulder to fall back on, so all the circlips will do is prove the point. Unless of course you find it expedient to circlip all your ammo.

Material for the circlip will be electrical copper wire, or hobby shop brass wire. Think old electric motor windings or multi-strand cable. In the first instance you can try .015" wire, but you may lose some of that .015" on chamber bevel, if the bevel is all the way around the chamber. If necessary use heavier wire. Leave a gap in the circlip for the extractor, though with the smaller wire you might get away without it.

I have a nagging suspicion that you may need to look further to solve the lockup issue, e.g. by swapping or polishing parts, but you can at least eliminate the headspace possibility first.

The image shows circlips that have been flattened because the wire was too thick, but you may not have to do that.

Incidentally, you can also run a headspace measurement without gauges by partially seating a primer in an empty case, preferably new, closing the action on the case, then afterwards measuring primer protrusion.

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Aaron posted this 24 March 2024

I read that post and am amazed at the ingenuity our members show in problem solving skills. I have a few things to try first before the case setback with a c-clip. Thanks for the reply and the reminder that this may prove concept.

 

With rifle in hand, I confidently go forth into the darkness.

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Clod Hopper posted this 24 March 2024

You do have excess headspace aggravated by the thin rims on your cases.  You should not be able to move the bolt like that. That sounds excessive to me.   A heavier load would cause the extruded primers to be fully seated after firing.  This does not solve the problem though.  At full power the brass moves forward, the pressure pushes the primer back since there is nothing to stop.  The brass case clings to the chamber walls for a miilsecond and only after pressure gets higher does it slam back in the breech block.  This reseats the primer, but you may get a flattened primer that looks like excess pressure.  You could only partially size the cases so that the case headspaces on the shoulder like a .30-.06.  That may work for your currrent load.  The .38-55 headspaces on the rim.  You could also find some thicker brass, maybe some .30-30, or .375 Winchester.  If it were my rifle, I might send it back.  At least have a gunsmith look at it.

Dale M. Lock

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Aaron posted this 24 March 2024

That feed issue was corrected on both rifles by filing a radius on the breech face like actual Winchester rifles have in their 38-55 rifles. The first rifle would not chamber a cartridge at all. Can’t believe it made it on the boat like that.

With rifle in hand, I confidently go forth into the darkness.

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pat i. posted this 24 March 2024

I dug out some WW once fired 38-55 brass if you want to try 10 of them. The rim is .055- .058 thick so you might not see any difference from what youre using now but the offer's there. The one I measured was 2.075 long.

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Aaron posted this 24 March 2024

That is a very kind offer. Let me putz with some other options first.

With rifle in hand, I confidently go forth into the darkness.

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pat i. posted this 24 March 2024

No sweat but the offer's there.

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Wilderness posted this 24 March 2024

 

MP1886

These big blocks of italicised text are difficult to untangle.

With the best possible intentions, and with a background including editing, I can offer some suggestions. Having opened the gate, I will of course expect some of the same in return.

The first suggestion is to reduce the quote to just that part of it to which you are replying. The unwanted parts can be edited out before you start on your own reply.

The next suggestion is to separate the italicised quote from the text of the reply by removing the italics on the reply. Now we can see who said what.

The last suggestion concerns sentence length. Even if you start with long sentences, go back over your work and cut them up into shorter ones. Anything over about 20 or 30 words needs a second look. That said, I can see that my post ended with a long sentence. This just goes to show that sentence length requires discipline.

 

 

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Ken Campbell Iowa posted this 24 March 2024

looks like too much bolt-to-head clearance ....   " headspace " for our purpose ... ...

i would establish this first so that you can move directly to the next decisions.

a decent kitchen table crutch to check this is to cut little squares from a business card and use fast dry fingernail polish to glue them on the back of a case or cartridge ...  these will usually mike from 3 to 5 thousandths each.   

if you reload cases you really need not over 0.004 clearance  ...  the brass is going to be stretching when you fire it ... as described above the brass is shoved forward then it sticks at the front  when fired and at some pressure the back of the case is stretched back into the bolt.  at some less pressure the brass is not stretched but the primer is blown out the back a little to hit the bolt.

at low cast loads some grease the case and avoid stretching ...  at high pressures this crutch might peen the rifle parts eventually ... 

***************************

if you dont reload you can grit your teeth and get by with 0.008 or 0.010 head clearance ...  probably wont seperate new factory brass but just not a good feeling thing to do.

above 0.010 static head clearance you really need to tighten that clearance.,  for one thing a lever action rear locker metal is going to stretch a little more to add to the case stretch.

**************

i am not a lever action fixer guy, but the cheapest simple fix might be to braze a little metal to the locking bar and then file and lap back to a snug lockup ...  

enjoying this thread and hope this helps.

ken

 

 

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Premod70 posted this 25 March 2024

The primer protrusion is excessive headspace when seen on a rimmed case and no work around will safely solve the problem; send the rifle back.

Forrest Gump is my smarter brother.

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MP1886 posted this 25 March 2024

looks like too much bolt-to-head clearance ....   " headspace " for our purpose ... ...

i would establish this first so that you can move directly to the next decisions.

a decent kitchen table crutch to check this is to cut little squares from a business card and use fast dry fingernail polish to glue them on the back of a case or cartridge ...  these will usually mike from 3 to 5 thousandths each.   

if you reload cases you really need not over 0.004 clearance  ...  the brass is going to be stretching when you fire it ... as described above the brass is shoved forward then it sticks at the front  when fired and at some pressure the back of the case is stretched back into the bolt.  at some less pressure the brass is not stretched but the primer is blown out the back a little to hit the bolt.

at low cast loads some grease the case and avoid stretching ...  at high pressures this crutch might peen the rifle parts eventually ... 

***************************

if you dont reload you can grit your teeth and get by with 0.008 or 0.010 head clearance ...  probably wont seperate new factory brass but just not a good feeling thing to do.

above 0.010 static head clearance you really need to tighten that clearance.,  for one thing a lever action rear locker metal is going to stretch a little more to add to the case stretch.

**************

i am not a lever action fixer guy, but the cheapest simple fix might be to braze a little metal to the locking bar and then file and lap back to a snug lockup ...  

enjoying this thread and hope this helps.

ken

 Thanks for this post Ken, it's what I've been saying all along. My test was the oiled case.  If when fired the primer is flush, then the problems it excess headspace. Leaving little of the case lube on the case or lightly oiling them will solve the problem too as then the case will be driven back instead of obturate and stretching. Okay for light/medium loads, but eventually put more strain on the bolt lock up. 

 

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Rich/WIS posted this 25 March 2024

Sounds like the primer is protruding enough to bind against the bolt face.  When you drop the hammer again you are moving the primer forward enough to release the pressure on the bolt face and it opens.  I'd call Cimarron/Uberti and see what they say, maybe send it back with several fired cases so they can see the problem.  Hopefully they have good customer support.

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