The Firing Line Forums - View Single Post - primer seating depth, flush with base, causing misfire problem?

**Unclenick** · June 9, 2014, 02:42 PM

I think Weshoot2 is right. Especially if you've reloaded these several times and have yet to clean the primer pockets out. If that crud gets thick enough, it can cushion the primer some. So, every once in awhile it may be worth decapping separately and scraping them out. But more important, by seating shallow, you are asking your firing pin to finish seating the primer before the remaining energy can ignite the primer, and that's a recipe for failure to fire.

For reliability, primers should be a minimum of 0.002" below flush to a maximum of 0.006" below flush according to Olin's (Winchester) military primer specs. What you are actually trying to do is get an optimal amount of squeeze between the tip of the primer anvil and the inside of the cup preloading the primer mix. This is called setting the bridge (thickness of the amount of priming mix between those two pieces of metal). In practical terms, if you don't have a press that controls this, it just means seating hard. You can read about it here.

June 9, 2014, 02:42 PM	#8
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	I think Weshoot2 is right. Especially if you've reloaded these several times and have yet to clean the primer pockets out. If that crud gets thick enough, it can cushion the primer some. So, every once in awhile it may be worth decapping separately and scraping them out. But more important, by seating shallow, you are asking your firing pin to finish seating the primer before the remaining energy can ignite the primer, and that's a recipe for failure to fire. For reliability, primers should be a minimum of 0.002" below flush to a maximum of 0.006" below flush according to Olin's (Winchester) military primer specs. What you are actually trying to do is get an optimal amount of squeeze between the tip of the primer anvil and the inside of the cup preloading the primer mix. This is called setting the bridge (thickness of the amount of priming mix between those two pieces of metal). In practical terms, if you don't have a press that controls this, it just means seating hard. You can read about it here. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; June 18, 2014 at 07:29 AM.