Breech Face Pitting

[Ancient One]

What causes a circular ring of pitting on the breech face? This pitting is the approximate outside diameter of the primer. It is occuring on 2 open guns,.38 super & .38 super comp,a .40 limited gun & a .45 ACP. The limited & open guns have Caspian slides & the .45 is a Colt series 70 slide. I am very careful with my loads,never using a load not listed in a manual(I have been reloading for 42 yrs.) I use mostly Federal primers esp. when getting within 10% of max as Federal is softer & shows pressure quicker. My limited gun is showing this pitting in 3000 rds from new.

[Flexmoney]

Are you using Magnum primers? Or, Small Rifle primers?

The usual cause of the pitting is gas getting past the primer. The reason is that there isn't enough pressure to seal the primer walls to the primer pocket.

[Ancient One]

Are you using Magnum primers?  Or, Small Rifle primers?

The usual cause of the pitting is gas getting past the primer.  The reason is that there isn't enough pressure to seal the primer walls to the primer pocket.

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I am using small or large pistol primers as required by the cartridge. No magnum or rifle. Could the non-sealing be due to the lower pressure loads I normally use? How about looser primer pockets sometimes found in picked up range brass?

[kevin c]

Scrounged range brass of questionable provenance might be one problem. How do the primers seat? Do you feel resistance when seating, or do they slip right in?

[Ancient One]

Scrounged range brass of questionable provenance might be one problem. How do the primers seat? Do you feel resistance when seating, or do they slip right in?

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Am using a 650. Most have a reasonably tight feel,some more than others. Nothing really loose,I discard if so. I have some 1x fired Fed. & PMC .40 brass. I will switch & use only this for the next few thou. rds.

[cking]

I was re reading Feamster book. He remarked that with Federal primers he was getting a crater face. Switch to Winchester and problem went away. Also I would deprime some of brass and inspect primer pocket. Causes are loose pockets, crud in pocket, and hard primer skirts.

[eric nielsen]

Switch brands, polish your breachface, and see what happens. WSR works well.

Federal Large Pistol primers really messed up the breach of my Glock20 in 10mm.

[Ancient One]

Switch brands, polish your breachface, and see what happens. WSR works well.

Federal Large Pistol primers really messed up the breach of my Glock20 in 10mm.

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Post #6 & 7 give room for some serious thought. I have almost always used Federal Pistol primers. I have Feamster's book. Will check it. Also will go to once fired or new brass + change primers + try the other things suggested. Thanks guys. Ancient One

[benny hill]

Usually on open guns people are useing to fast a powder with to much pressure & blowing past the primers. If you use range brass that has enlarged primer pockets from high pressure , the pockets will be to loose to seal primers in any cal.

[Flexmoney]

To add to the above good info...

Could the non-sealing be due to the lower pressure loads I normally use?

Yes, I would think so.

[Ancient One]

Usually on open guns people are useing to fast a powder with to much pressure & blowing past the primers. If you use range brass that has enlarged primer pockets from high pressure , the pockets will be to loose to seal primers in any cal.

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I only use the slow burning powers. N 105 @ 10 gr for matches to make major,this is their starting load. Also can do with SP-2 & 3N38 but only at the top of the manual. I use 7.3 of N350(not major)for practice. I have a 4-port bbl & do lose some there. Lil Gun won't even come close. I use MT Gold 124 HP.

[fishnfst]

Thats not pitting, its gas cutting.... Fairly common in rifles with higher pressure loads like some of the .17 cal wildcats .17 hornet and larger, mach IV, remington, br and the such... All you can do is play around with the primers and see if you can find something that seals better with the higher pressures... From memory we used to use a lot of Remington 7.5's in the rifles but it's a matter of experimentation.....