Hey y'all, my Cimarron '73 developed a bit of a problem recently in that .357 Magnums shot through it will result in bulging cases, and in the case of Sellier & Bellot, full on case head separation.
Here's the remains of the S&B brass:
And here's a piece of Federal brass, where you can see it bulged in the same spot the S&B brass separated:
Searching around and talking to other folks has suggested a few things:
1) Barrel is backing out, impacting headspace. This is being considered unlikely as the barrel is threaded into the receiver and the gun still shoots true with both .38 Specials and .357 Magnums, and the sights aren't canted at all.
2) Compromised/damaged chamber. This would make sense if the brass was breaking in a single point, rather than a consistent complete circle. I've inspected the chamber the best I can, and I see no irregularities in the metal.
3) Compromised headspace brought on by the toggle links not squaring up. This is kinda what I'm leaning to as I removed the links a few months back for cleaning, and it would certainly explain my foggy memory as I've been wondering just how long this problem has been going on as I simply can't recall
For what it's worth, the gun is short stroked with Pioneer Gun Works' super short stroke kit. Hopefully y'all can shed some light on this, cause I absolutely love the rifle and while I don't shoot Magnums out of it regularly, they're a hoot.