We finally found a 27 to test with. 15.3 grains of the IMR 4227 with Winchester mag primers flattened the first two primers With the same 158 grain .357 gas check bullets so we quit with them--but standard primers look normal with the same load. I can still use my 19 but brass is hard to eject so I will use it for 38 only. Mag primers with 4227 will raise pressure a lot in 357 with a full charge in this test. I switched back to 2400 that I have used since the 70s. No fault of the powder but maybe there should be warnings on the use of IMR 4227 with mag primers. Also my 19 -2 probably had who knows what shot through it. I have only had it less than a year and a beater when I got it.