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9/22/2017 12:11:25 AM
Posted: 3/13/2006 5:05:04 AM EDT
I shot my Yugo Mauser yesterday and notice something that bothered me. After each shot, I only fired two, I felt a burning sensation I suspec hot gases may be escaping from the rear of the bolt. Is that possible?

I haven't checked the headspace on this rifle. The recovered both casings and they aren't buldged or spilt. The prime isn't pushed out or blown. I did notice a lot of carbon build up on the exterior of the cases that may indicate gases venting. Any ideas other than not shooting it again until I check the headspace? Is this a common problem?

Link Posted: 3/13/2006 6:34:31 AM EDT


My guess is that you have a dirty/rough chamber walls, the carbon you see is from gas flowing back past the case. Normally the high pressure would be sealed off by the front half of the case, acting like an 'innertube' in a tire, because it gets pressed against the chamber walls.

Clean, inspect, polish if necessary.
Link Posted: 3/14/2006 5:16:14 AM EDT
I will try that. Definetly not a good feeling when shooting a rifle.


Link Posted: 3/14/2006 8:19:55 AM EDT
What kind of ammo? Old military arms usually have slightly larger chambers. In theory, and in practice, when the round goes off the brass expands to the chamber wall and seals the chamber from gas blowby. In a split second after the shot the case cools enough to shrink back a little so it can be extracted. You may have ammo that is underpowered or maybe a slightly large chamber. It may be possible to see correct headspace by a guage and still have a chamber that is slightly large.
Link Posted: 3/14/2006 10:04:41 AM EDT
[Last Edit: 3/14/2006 10:07:46 AM EDT by JIMBEAM]

Originally Posted By Hoppy:
What kind of ammo? Old military arms usually have slightly larger chambers. In theory, and in practice, when the round goes off the brass expands to the chamber wall and seals the chamber from gas blowby. In a split second after the shot the case cools enough to shrink back a little so it can be extracted. You may have ammo that is underpowered or maybe a slightly large chamber. It may be possible to see correct headspace by a guage and still have a chamber that is slightly large.



I was shooting Romanian steel cased 8mm.
Link Posted: 3/14/2006 10:55:40 AM EDT

Originally Posted By JIMBEAM:

Originally Posted By Hoppy:
What kind of ammo? Old military arms usually have slightly larger chambers. In theory, and in practice, when the round goes off the brass expands to the chamber wall and seals the chamber from gas blowby. In a split second after the shot the case cools enough to shrink back a little so it can be extracted. You may have ammo that is underpowered or maybe a slightly large chamber. It may be possible to see correct headspace by a guage and still have a chamber that is slightly large.



I was shooting Romanian steel cased 8mm.




I haven't shot any of the steel cased stuff yet. I do know that steel cases have a different expand/retract rate than brass though. You might try some brass cased ammo and see if it is any different. It may just be a combination of a slightly large chamber and the steel cases.
Link Posted: 3/14/2006 11:31:22 AM EDT
I've heard of the steel cased Romanian blowing back. I've never figured out exactly why it seems to happen in some guns and NOT others.

I have quite a bit of it and its not happened to me YET.

Dennis Jenkins


Originally Posted By JIMBEAM:

Originally Posted By Hoppy:
What kind of ammo? Old military arms usually have slightly larger chambers. In theory, and in practice, when the round goes off the brass expands to the chamber wall and seals the chamber from gas blowby. In a split second after the shot the case cools enough to shrink back a little so it can be extracted. You may have ammo that is underpowered or maybe a slightly large chamber. It may be possible to see correct headspace by a guage and still have a chamber that is slightly large.



I was shooting Romanian steel cased 8mm.

Link Posted: 3/14/2006 12:07:11 PM EDT

Originally Posted By djenkins:
I've heard of the steel cased Romanian blowing back. I've never figured out exactly why it seems to happen in some guns and NOT others.

I have quite a bit of it and its not happened to me YET.

Dennis Jenkins


Originally Posted By JIMBEAM:

Originally Posted By Hoppy:
What kind of ammo? Old military arms usually have slightly larger chambers. In theory, and in practice, when the round goes off the brass expands to the chamber wall and seals the chamber from gas blowby. In a split second after the shot the case cools enough to shrink back a little so it can be extracted. You may have ammo that is underpowered or maybe a slightly large chamber. It may be possible to see correct headspace by a guage and still have a chamber that is slightly large.



I was shooting Romanian steel cased 8mm.




It's kind of hard to miss when it happens. I bought a case I hope it works well in my other Mauser. Looks like I need to buy some of that brass cased stuff from AIM.
Link Posted: 3/14/2006 11:54:11 PM EDT
I’ve had no problems with the Romanian ammo (other than sometime wondering if it’s loaded with black powder since it’s so dirty!).

Still, I’d agree the problem is most likely the steel case not expanding enough (perhaps compounded by an oversize chamber?).

What you are describing is similar to the problem reloaders sometimes have when they underload their ammo.

What happens for them is there isn’t enough pressure to fully expand the case to seal off the rear of the chamber, thus gas and powder residue escapes to the rear, leaving a coating of black residue on both the outside of the case and on the shooter.
Link Posted: 3/15/2006 6:49:10 PM EDT
I think it's the ammo (can't say for sure w/o knowing how your gun checks out otherwise)

I have an RC K98 marked "AX" 1941 (Erma or "unknown") that gives me a gush of warm air with Romanian steel cased ammo but not the brass cased 1970s Yugo ammo.

Haven't had any problems per se, with either ammo in the rifle, no pressure signs and easy extraction and both are very accurate, but I suspect the Romanian allows a little more gas blow by
Link Posted: 3/15/2006 9:44:22 PM EDT
I've shot quite a bit of it and it doesn't blow back in my guns so far.

It would be interesting to compare a cerrosafe chamber cast of one that blows back vs one that never blows back.

I actually have some brass cased Romanian ammo. It came on nice strippers too. 1950's production. Much better ammo.

Dennis Jenkins


Originally Posted By steveinct:
I think it's the ammo (can't say for sure w/o knowing how your gun checks out otherwise)

I have an RC K98 marked "AX" 1941 (Erma or "unknown") that gives me a gush of warm air with Romanian steel cased ammo but not the brass cased 1970s Yugo ammo.

Haven't had any problems per se, with either ammo in the rifle, no pressure signs and easy extraction and both are very accurate, but I suspect the Romanian allows a little more gas blow by

Link Posted: 3/15/2006 10:08:51 PM EDT
If the exterior of the case body is dirty, then the case is not expanding enough to seal off the chamber. Gas is leaking past the case and venting into your face.

This sometimes happens when reloaders use too little powder and the cases come out "sooty". It could also be your steel cases are stiffer than a brass case combined with a "generous" chamber dimensions resulting in a poor seal.

It's just a theory.
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