KKM Glock barrels do provide more case head support than Glock gen 3 and earlier barrels, but I don't think there is a big difference between aftermarket barrels and gen 4 or later barrels in terms of case head support. I am not in favor of hot rodding an already high pressure cartridge like the 40 S&W. Yes, you can play games with longer OAL's and gain some velocity, but don't try to turn the 40 S&W into a 10mm Auto. You may end up with a spare parts pistol.

Large primer vs small primer has nothing to do with case head strength. The reason for the large primer in the 10mm is for more uniform ignition of a long column of the relatively slow burning powders used in full power loads. The 40 S&W uses a small primer because the powder column is shorter and the powders used are typically in the medium burning range. It has nothing to do with case strength.

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VCDL, GOA, NRA