In one of their recent manuals, Speer warns against using some of their loading data in .40 S & W pistols which don't completely support the cartridge head, saying that doing so could lead to bulged cases or head separation. Hodgon seems to pick up on this idea, but neithe Sierra nor Nosler do.

Does anyone know anything about this? Especially, which pistols do not completely support the .40's cartridge head, and how big a problem this is (i.e. is there anyone who knows of someone who has experience either case bulging or head separation, using loads listed in manuals).

Thanks.

Clawmute

My stock Glock 40 S&W barrel had a feed ramp intrusion of .235".

The typical 40 S&W case has a web that is .180" thick.

This left .055" of thin unsupported case wall.

As I worked up a load, the fired cases displayed the malady "guppy belly" case bulge in the shape of the feed ramp.

This problem showed up at about 125% powder charge compared to maximum published load.

With a barrel change that supported to the web, I was able to shoot 246% powder charges [all that I can get to fit] without case failure.


In order to duplicate my case support measurements, remove the barrel from the pistol.
Place a case in the chamber.
Scribe the outline of the feed ramp on the case with a needle.
With height gauge, dial or digital calipers, measure the distance from the back of the case to the top of the scribed line.
Cross section a case.
Measure the distance from the back of the case to the front of the web where the case wall gets thin.

Don't try to duplicate my overloads if you don't know what you're doing.

Yes, this can be a problem. It often comes up when using full power factory loads or full power eqiv. handloads & the bullet sets back into the case, sometimes dramaticaly raising pressures. Also if you hot handload cases that have come from an unsuported chamber too many times, it does weaken the brass in the critical web area. If you are cautious in your handloading (watch your OAL & case neck tension, check your brass) you should have no problems. I also like using powders on the med.-slow side for full power loads. The pressure curve is not as steep & will keep you out of trouble if a bullet does setback.

Thanks guys. I really appreciate this, and so will my shooting buddies.