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1) If the guy running the lathe uses a standard go gauge to headspace an Ackley chamber, the case will stretch too much in fire forming and get frequent case separations just behind the shoulder. This problem is common as dirt.
2) I have tried ~~ 100 fixes and the best I have found is 10 gr of any pistol powder [that would be 5 gr for .223] covered with cream of wheat and fired without a bullet.
3) The case is slathered with a film high pressure lubrication like moly grease. This forms half a shoulder and does not stretch the case too much behind the shoulder. That half shoulder can stand up to the push of the firing pin. That is unlike the base of the case neck cannot stand up to the sharp shoulder neck base and there will be a ring of plastic deformation.
4) Ackley chambers should be headspaced so new brass crushes .004" [on bolt closing] at the base of the neck. The case then does not move forward on fire forming with the tighter headspace.
5) The half formed shoulder can be full power with bullets with full accuracy. There will then be a full shoulder for the 3rd firing.
6) There are other good fixes. A mandrel can open up the case neck that can then be partially full length resized so that there is .004" of crush on bolt closing. Or the barrel can be set back .004".
You're making this into something it isn't. One beauty of these chamberings is that they're just stupid easy.......for most people.
1) You got this one right.
2) Unnecessary and a complete waste of time and whatever components you're using.
3) Stupid and completely unnecessary.
4) People love to parrot the .004" number........this is also "common as dirt." It would work "ok" if every case were exactly the same, but they're not. Try measuring brass. A new 223 case headpaces on the neck/shoulder junction in an AI case. It has to fit with crush. I pulled 20 unfired 223 cases, 2 different headstamps (Lapua gold box and IMI SS109) and measured them........... headspace varied by .007" between longest of one and shortest of the other. A chamber cut .004" short of some fixed gauge is wrong. My own 223AI chambers are cut with .015" crush. That's not too much and there's very little bolt pressure.
5) " Half formed shoulder?" "Full shoulder on the 3rd firing?" What??? You load 'em with bullets and shoot 'em. Perfect shoulder. That's all there is to it.
6) First, you better damn well set the barrel back.......that's how it should be done in the first place. Makes the rest of this nonsense.
