I bought 3 Glocks 15 years ago, with different case supports:
1) Glock 19 9mm feed ramp intrusion 0.190", case web thickness 0.160" -> 0.030" of thin case wall unsupported, can shoot 60% extra powder before case bulge
2) Glock 22 40sw feed ramp intrusion 0.235", case web thickness 0.180" -> 0.055" of thin case wall unsupported, can shoot 25% extra powder before case bulge
2) Glock 20 10mm feed ramp intrusion 0.250", case web thickness 0.180" -> 0.070" of thin case wall unsupported, can shoot 3% ~ 10% extra powder before case bulge
What have I done about this?
1) G19 9mm .. I made a 48 pound triple recoil spring assembly. I put in a New York Trigger to reset as fast as the recoil spring pushes the slide. I doubled the magazine springs in parallel to keep up with the slide speed so the chamber would not come up empty. I have never seen anyone be me with strong enough grip to chamber a round. This is all tuned up for 20% extra powder. This means the stock case support is up to anything theoretically possible in this pistol. The only reason for an aftermarket barrel would be; length, muzzle threads, accuracy, leading, etc. But not case support.
2) G22 40sw... The chamber was not only instruded, the rear inside diameter was larger than SAAMI spec tolerances. Almost all chambers are at the small end, this is very unusual to see something too big. I TIG welded up the feed ramp and re cut the chamber and feed ramp at .180" -> 0.000 unsupported case wall. It can now shoot 154% extra powder.
3) G20 10mm....I bought a Bar Sto aftermarket 10mm barrel with 0.230" feed ramp intrusion -> 0.050" unsupported. Can now shoot 50% extra powder. I also Bought a KKM aftermarket 40sw barrel for the G20 with feed ramp intrusion of 0.200" -> 0.020" unsupported. I have not shot the KKM, but I would assume it can take 100% extra powder if anyone could take the recoil. With the 1.3" OAL and stronger 40sw case head, I could potentially chrono the highest power that ever came out of a G20 with 4.5" barrel.