ChauChat Assistance Please

[oprod]

Gentlemen, Have a small conundrum Im hoping someone else has crossed.

Ive got a Chauchat that runs solidly on old ammo made in the 1938 i believe.

Of course I am getting low on ammo, Ive purchased new lebel brass, and bullets from privistan for the lebel.

Ive reloading these to the specs, but Im now getting what im assuming is premature extraction. the cartridges seem to come out of the chamber partways before the pressure is redused enough. The result is the case shoulder being blown out well above what it was before firing. The cases seem to have moved 3/16 rearward before expansion takes place. it also swells the base of the cartridge that is out of the chamber a bit. Now I admit freely to the following, Im using powder from pulled lebel cartridges that the berdan primers have failed in. Im using the same grains that came out of the old cartridges into the new cartridges.

Im wondering if this might be an issue that the new brass is softer? Is the effect Im seeing of not enough pressure? Too much pressure?

[Black River Militaria CII]

The breech is locked on firing so the delay in opening as the breech unlocks should be sufficient for pressures to reduce to safe levels. If headspace is correct, which seems to be the case if vintage cases are not swelling the same way, my suggestion would be to reduce the power charge a few grains and see if the case swelling continues the same or is reduced.
Privilege brass is very soft compared to vintage French cases which is going to increase the potential for blowing out. If I recall the case thickness at the base of the Priv is fairly thin.
I suggest checking the headspace carefully to eliminate that as a contributing factor.
As manufactured, Chau Chau barrels had a thin raised rim around the mouth of the chamber, similar to the Lewis breech, to support the wall at the base of the case. The rim of the case headspaced against this rim which kept the case rim away from the breech face to provide a gap for the extractor. Reactivated Chau Chaus with barrels that that were restored did not include recutting the breech face with the rim. The welding of the chamber mouths destroyed the raised rim and the person doing the barrel restoration did not know about the rim. In order to restore the rim, the breech face needs to be cut back leaving the rim with sufficient height to provide the extractor gap and the chamber deepened for correct depth with the rim. In restored barrels, without the rim, the gap was provided by cutting a recess around the chamber mouth that was a bit longer than the arc through which the extractor rotated between unlocking and locking of the bolthead.
If the rim is Cut in the breechface and the headspace is a bit too long, the exposed soft brass of the Privi cases might not be able to resist the pressure.
The way the headspacing works on the Chau Chaus, there is enough available axial play in the barrel with the headspace locking collar for any barrel to be recut with a rim if needed.
Hope this is helpful......

Edited September 17, 2017 by Black River Militaria CII

[oprod]

Bob, thank you for taking the time to reply, I will check these things and report back in time.

[wwiifirearms]

I recently did a REWAT on a Chauchat (with lots of help).

What projectiles are you using?

 

I had a new barrel made and installed on mine to shoot the common .323 bullets, which is what PPU is using for their Lebel ammo. Original ammo I believe is .325

Is it possible that with .323 bullets you are getting less pressure than with the old ammo, causing it to open too soon?

[waterdawg2004]

Not sure about what Bob said about the breech face but this is what mine looks like, it has a cut out for the extractor.

[waterdawg2004]

The breech is locked on firing so the delay in opening as the breech unlocks should be sufficient for pressures to reduce to safe levels. If headspace is correct, which seems to be the case if vintage cases are not swelling the same way, my suggestion would be to reduce the power charge a few grains and see if the case swelling continues the same or is reduced.

Privilege brass is very soft compared to vintage French cases which is going to increase the potential for blowing out. If I recall the case thickness at the base of the Priv is fairly thin.

I suggest checking the headspace carefully to eliminate that as a contributing factor.

As manufactured, Chau Chau barrels had a thin raised rim around the mouth of the chamber, similar to the Lewis breech, to support the wall at the base of the case. The rim of the case headspaced against this rim which kept the case rim away from the breech face to provide a gap for the extractor. Reactivated Chau Chaus with barrels that that were restored did not include recutting the breech face with the rim. The welding of the chamber mouths destroyed the raised rim and the person doing the barrel restoration did not know about the rim. In order to restore the rim, the breech face needs to be cut back leaving the rim with sufficient height to provide the extractor gap and the chamber deepened for correct depth with the rim. In restored barrels, without the rim, the gap was provided by cutting a recess around the chamber mouth that was a bit longer than the arc through which the extractor rotated between unlocking and locking of the bolthead.

If the rim is Cut in the breechface and the headspace is a bit too long, the exposed soft brass of the Privi cases might not be able to resist the pressure.

The way the headspacing works on the Chau Chaus, there is enough available axial play in the barrel with the headspace locking collar for any barrel to be recut with a rim if needed.

Hope this is helpful......

Bob do you have a picture of what the breech face should look like? Thanks

[wwiifirearms]

First two are the new barrel I had made. Last one is an original.

[waterdawg2004]

Ok thanks. I see the raised rim now on mine which I had not noticed. The breech on these barrels also have a cut out for the extractor on all of these barrels.