I had a partial case head separation using a 1.8oz buffer

[DeNinny]

The case head didn’t expand into the extractor. Look at this image:



The extractor was pulling with such force on the case, that it stretched the side wall, causing the side wall to literally rip apart with a fine, thin line.

I couldn’t see this from the initial pictures, but the more recent one shows it clearly where you can see the case head from the rear, as well as the tear.

Residual pressure folded the brass from that failure point backwards as the spent case was being extracted.

The is textbook partial case head separation, which is almost always a gas system issue in self-loaders.

Since these were first loads, virgin brass, incipient case web weakening isn’t an issue because the brass has not been hot and cold-worked repeatedly.

With a choked gas system or port work and heavier action spring, the problem should go away and brass will come out nice and clean, ready for many more loads.

You have to take the whole system into consideration, and we wasted 8 pages talking about things that I think were totally unrelated to the failure.

This was a major problem in the Colt 602 rifles in Vietnam before the M16A1 development corrected all those issues.

They had rough chambers, minimum or less-than-minimum spec chambers, lightweight Edgewater spring guides, certified with stick powder in the States, then sent to Vietnam and fed ball powder cartridges.

They were ripping case heads off, slipping extractors over rims and FTExtracting with next round feed into the stuck case, and partial case head separating.

His brass actually looks like the chamber is very clean.

Once the projectile passes the gas port and then leaves the muzzle, all the gas pressure has NOT subsided.

The gas volume is directed back through the tube into the expansion chamber with enough mass and expanding energy to shove that carrier rearward at extremely fast speed, faster than your eye can track.

There is enough residual bore pressure during plug dwell time before the projectile exits to maintain significant pressure on the brass.

The timing of these events is within tiny fractions of a second, so there is room for an excessively-fast cyclic rate to cause violent extraction and subsequent damage to the case head.

I disagree. This picture fully supports what I've stated too. We will end up repeating ourselves now, so I'll leave it as we both have these models out there and others can take from it what they want.