Originally Posted by DWalt

If the cylinders were bulged, that powder is definitely not any kind of 4227, IMR, H, or anything else. As previously noted, virtually every top 4227 handgun load (and some smaller capacity rifle loads) will come close to filling the case, and therefore a double charge is just not possible. If it came from a new sealed can, I cannot imagine how it could have passed QA inspection, as powder manufacturers have very stringent controls to prevent such occurrences. And it's certain that the manufacturer would have already received similar reports from the field, and maybe even a few lawsuits. I think you should contact IMR. They will want to know about it. Possible that if the propellant is shown to be at fault, they might even spring for a new revolver.

PS: I have gone through much 4227 over the last 45+ years. It was the first powder I used when I began loading for the .44 Magnum (back when it was still being made by duPont), and I have used it since for .30 Carbine and also for cast bullet loads in .30-30, .308, .300 Savage and .45-70. I have seen very little difference between identical loads using H4227 and IMR4227. In the .30 Carbine, you need to fill the case almost to the case mouth with 4227, and even so, the MV is still somewhat below that of recommended loads using H110.