First Case Head Separation

[bigedp51]

Any chance on that case you coulda forgot to remove the case lube?

That is possible. I am shooting 185 cases with this barrel. I went through them all looking for an external ring. I found five. I could just barely feel a little catch on four and one is really bad. It has a very clear grove around the exterior. I am going to open it up tomorrow. Later! Frank

The premise behind lubing cartridge cases is that they do not grip the chamber walls and slide back against the bolt face without allowing case stretching. The problem with lubing the case is it nearly doubles the bolt thrust and adds more stress to the bolt and receiver in many cases.

On top of this when a chamber is made it can be rough as a cob to as smooth a chromed chamber and be as slippery as snot on a door knob. Meaning chamber finish also effects bolt thrust and the dwell time the rear of the case is in contact with the bolt face.

Also if enough case lube, oil, bore cleaning solvents or water is present when the case expands when fired it will force the oil, lube or water in front of the bullet and cause a unwanted pressure spike.

Bottom line if any remaining lube was still on the case it didn't cause the case stretching. The cases either stretch on the first firing and started the problem or the cases had the shoulder pushed/bumped back too far during resizing.

Its a balancing act between chamber pressure and head clearance, I have 30-06 cases fired in my M1 Garand with far more shoulder bump used by many of you here and no case head separations. And using the RCBS Case Mastering Gauge will tell you far more than a bent paper clip.

 

[22BRGUY]

I stand corrected....case lube was probably not the cause of the problem. I do remember that on 22 250s, they seemed alot more prone to case stretching even when only bumping the shoulders one or two thou. Some brands of brass also seemed to grow at different rates.

Anyway, thanks for correction and clarification and best wishes on discovering the problem.