I loaded up 50 rounds of 500 magnum today to try out my new toy at the range. The recoil was not nearly as stout as I was expecting, given all the hype. My 15YO daughter even shot it a few times 
Loads:
(25) 46gr of 300MP under 350gr Berrys, Winchester Large Rifle Magnum primer (3 grains under Alliant max load)
(25) 25gr Power Pistol under same bullet and using same primer (two grains under Alliant max load)
Easily 20% of the rounds didn't fire on first single action attempt but would always fire when hit a second time. I attempted a full cylinder in double action, not one fired. Back around a second time in single action, all 5 fired.
All the Power Pistol rounds, after firing, had fairly clean cases and no flattened primers. No apparent powder burns on the outside of the cases.
3-4 of the 300MP rounds had VERY flattened primers, the rest looked fine. The ones that flattened were also a challenge to extract. They had powder burns back on the case which caused the sticking so I don't think it was overly excessive pressure. As soon as I tapped the extractor the case 'broke loose' and extracted just fine. I found the 300MP powder in my 44 magnums to be very dirty also, but this looked like the powder was still burning as it came back into the cylinder. Every one of the 300MP cases have some discoloration/burn marks on the outside.
1. I carefully measured the powder, checking the throw weight every 3 rounds. I also visually inspect the charges of all cases before I seat bullets. Of course I likely wouldn't see a tenth of a grain difference, but I surely would have seen something that caused a louder bark and flattened primers on the 3-4 rounds.
2. I always check the primer seating depth.
3. I've been reloading since the mid-80s and I'll bet I haven't had five total failures to fire. Today I had at least ten.
Any thoughts on the failures to fire? Maybe Winchester cups are just that hard? The Alliant data used Federal 215 LRM, are they softer? Has anyone had an issue with FTF and Winchester primers? It's especially odd that NO double action shots lit off at all. Not that I'm going to be meeting a bear any time soon but it sure would stink to have 5 clicks and no bangs in that situation!
Loads:
(25) 46gr of 300MP under 350gr Berrys, Winchester Large Rifle Magnum primer (3 grains under Alliant max load)
(25) 25gr Power Pistol under same bullet and using same primer (two grains under Alliant max load)
Easily 20% of the rounds didn't fire on first single action attempt but would always fire when hit a second time. I attempted a full cylinder in double action, not one fired. Back around a second time in single action, all 5 fired.
All the Power Pistol rounds, after firing, had fairly clean cases and no flattened primers. No apparent powder burns on the outside of the cases.
3-4 of the 300MP rounds had VERY flattened primers, the rest looked fine. The ones that flattened were also a challenge to extract. They had powder burns back on the case which caused the sticking so I don't think it was overly excessive pressure. As soon as I tapped the extractor the case 'broke loose' and extracted just fine. I found the 300MP powder in my 44 magnums to be very dirty also, but this looked like the powder was still burning as it came back into the cylinder. Every one of the 300MP cases have some discoloration/burn marks on the outside.
1. I carefully measured the powder, checking the throw weight every 3 rounds. I also visually inspect the charges of all cases before I seat bullets. Of course I likely wouldn't see a tenth of a grain difference, but I surely would have seen something that caused a louder bark and flattened primers on the 3-4 rounds.
2. I always check the primer seating depth.
3. I've been reloading since the mid-80s and I'll bet I haven't had five total failures to fire. Today I had at least ten.
Any thoughts on the failures to fire? Maybe Winchester cups are just that hard? The Alliant data used Federal 215 LRM, are they softer? Has anyone had an issue with FTF and Winchester primers? It's especially odd that NO double action shots lit off at all. Not that I'm going to be meeting a bear any time soon but it sure would stink to have 5 clicks and no bangs in that situation!
