#1. It's not the primers.
I've personally used nearly 40,000 Winchester large pistol primers in the last 10 years shooting bullseye and have yet to have a dud. I have used upwards of 250,000 various makes and sizes in the last 35 years of reloading and cannot honestly remember one dud primer. A long time ago I intentionally loaded with oily hands & fingers, trying to MAKE a dud primer in a cartridge. I had heard for years that you needed to have nearly surgically clean hands so you didn't contaminate the priming mixture. I couldn't do it, not to say it can't be done, but I couldn't. I quit worrying and just loaded. Now I load everything with Dillon 550's and an RCBS 4x4 so the amount of contact I have with the primers is very minimal.
Without a little more information about the loading setup, I tend to think there is something else in the process that is affecting your ammo.
What type of bullets are you loading? And, what seating depth is being used? If you're using a lead SWC design, seat them so there is 1-2 thumbnail thickness' of lead exposed.
What amount and type of powder are you using?
In my experience, case length means nothing in the 45 ACP. I have yet to measure a 45 case, other than wall thickness. If you were shooting a precision rifle, trimming to one given length is beneficial. On a pistol that is being used at 25 yards or less it makes no difference. At 50 yards, out of a Ransom rest with several custom 1911's, I haven't been able to show any improvement, and I've tested thousands of rounds. The most I will do for my long line loads (50 yards) is use the same brand of case for that match. The next match it may be another brand, but the powder charge, primer, and bullet remain the same.
If you mark and remeasure your .886 cases after many firings you'll find they have shrunk. A straight wall pistol case does that, they shrink not grow, unlike bottleneck cases.
Good luck in your quest.
FWIW
