A small piece of media stuck in the hole at the primer cup side would be centered over the middle of the primer anvil, which is a depression, and so might cause no seating interference. I am surprised the primer didn't just blow it through, though. Were their any carbon marks around the primer itself to suggest gas leaking out around its edges?
Visual inspection of charges is a pretty good indication none were undercharged.
Powder contamination was mentioned earlier. I had a minor cold one time and had a drop fall from my nose into a case I was inspecting, boogering the powder up. A drop of perspiration would do the same thing, albeit not so literally.
I put your load into QuickLOAD. If it's database is correct that your bullet is 0.515" long, then you should have about 47% case fill of the space under your bullet with your COL, and there's no way powder position alone should have affected your round so dramatically. Lots of common target loads have loading densities in that range. It's too small for rifle powders, but quick pistol powders don't usually mind. However, if you combine powder being forward against the bullet with a plugged flash hole, perhaps the two in unison would conspire to delay delivery of primer gas enough to let it cool some and produce this result.
Anyone who has fired an uncharged pistol round knows a primer makes enough gas to unseat a bullet just fine, and if the powder burn doesn't get underway until after that unseating has started, the expansion plus the gas leaking around the bullet can prevent pressure from building. BTW, you didn't mention your primer. Magnum primers, because they make a larger volume of gas, can actually worsen this problem in some instances, causing lower rather than the expected higher peak pressure.
Visual inspection of charges is a pretty good indication none were undercharged.
Powder contamination was mentioned earlier. I had a minor cold one time and had a drop fall from my nose into a case I was inspecting, boogering the powder up. A drop of perspiration would do the same thing, albeit not so literally.
I put your load into QuickLOAD. If it's database is correct that your bullet is 0.515" long, then you should have about 47% case fill of the space under your bullet with your COL, and there's no way powder position alone should have affected your round so dramatically. Lots of common target loads have loading densities in that range. It's too small for rifle powders, but quick pistol powders don't usually mind. However, if you combine powder being forward against the bullet with a plugged flash hole, perhaps the two in unison would conspire to delay delivery of primer gas enough to let it cool some and produce this result.
Anyone who has fired an uncharged pistol round knows a primer makes enough gas to unseat a bullet just fine, and if the powder burn doesn't get underway until after that unseating has started, the expansion plus the gas leaking around the bullet can prevent pressure from building. BTW, you didn't mention your primer. Magnum primers, because they make a larger volume of gas, can actually worsen this problem in some instances, causing lower rather than the expected higher peak pressure.
