Primer marked on the breechface.

[yuthh]

I dont know a right word to call this mark on the breechface in my open gun so I call it primer marked.It looks horrible.But it doesn't look that bad in my limited gun.Both have pretty much identical round count.I have seen Clark has a firing pin hole replacement kit at Midway.Will it fit for replacement?

What do you think that would possibly cause this mark?Too soft or too hard primer possible?How do you fix it?

Thanks for any input.

Yuthh

Edited November 13, 2010 by yuthh

[yoshidaex]

Pictures?

From sounds of it, breech face erosion due to gases getting by the primer/pocket seal.

[Kyle O]

Breechface erosion, brass is worn out.

[yuthh]

Pictures?

From sounds of it, breech face erosion due to gases getting by the primer/pocket seal.

I dont have a picture cause the slide was sent to refinishing.

[yuthh]

Breechface erosion, brass is worn out.

I am pretty sure they were no more than 2 times reload.By the way I shoot 38sc.

[yuthh]

Dont you think it has anything to do with primers?

I used Federal samll pistol with open 9mm major Glock.I had problably 5k through it.Breechface still look normal.With 2011 open I have been using Federal Magnum and CCI small rifle.After 5k it's shown some deep round marked around the firing pin hole area.

[mike cyrwus]

smaller primers and bigger holes equals more gas equals more erosion.

definitely could contribute to it.

Ill bet powder choice is a variable that can be tweaked as well.

[GrumpyOne]

Dont you think it has anything to do with primers?

I used Federal samll pistol with open 9mm major Glock.I had problably 5k through it.Breechface still look normal.With 2011 open I have been using Federal Magnum and CCI small rifle.After 5k it's shown some deep round marked around the firing pin hole area.

The small pistol primers are softer than the rifle and CCI primers, creating a better seal when fired. The small rifle and CCI primers don't seal as completely, leaving room for gas to blow by them, creating breech face erosion.

[yuthh]

That makes sense.

[GrumpyOne]

Alot of people are running SRP in their open gunsm but then again, they also have some serious pressure going off in their hands when the pull the trigger. I would suggest, if you aren't running around 40,000 PSI, to use small pistol or small pistol magnum primers in all of your loads. Preferably Winchester brand, they seem to have the best hardness/softness ratio (IMO). Federals are notoriously soft, CCI are notoriously hard. Winchester is the porridge that is just right. With the SPM primers, they are just a tad harder than the SP, and not quite as hard as the SR's. A plus with the SPM primers is that you can drop your powder charge just a bit, cause they will give you about 10-15 FPS extra on average.

[CocoBolo]

I don't want to start a Riot here, but my smith and I had several discussions on this very subject. Open guns tend to put the impression of the round on the breech face. I just built a new gun using a Caspian slide because according to my smith they are harder than STI and SVI. Now let me add that some STI/SVI are harder than others and he says he notices this when milling slides. All 3 of my STI slides have those doghnut impressions, however the new caspian does not but it only has 500 rounds on it as of today. My limited gun does not have the impressions.

I had a SVI with replaceable breach face I sold and the buyer managed to ruin two breech faces in short order dinking around with extra hot loads, when you get flow it tends mess up the firing pin hole.

My smith has a special drill bit that he fixes firing pin holes with, he had to fix his own gun when the pin started sticking.

[JThompson]

SOme info from past threads...

http://www.brianenos.com/forums/index.php?showtopic=101751&st=0&p=1160502&hl=breechface%20erosion&fromsearch=1entry1160502

http://www.brianenos.com/forums/index.php?showtopic=67126&st=0&p=778701&hl=breechface%20erosion&fromsearch=1entry778701

[GrumpyOne]

I don't want to start a Riot here, but my smith and I had several discussions on this very subject. Open guns tend to put the impression of the round on the breech face. I just built a new gun using a Caspian slide because according to my smith they are harder than STI and SVI. Now let me add that some STI/SVI are harder than others and he says he notices this when milling slides. All 3 of my STI slides have those doghnut impressions, however the new caspian does not but it only has 500 rounds on it as of today. My limited gun does not have the impressions.

I had a SVI with replaceable breach face I sold and the buyer managed to ruin two breech faces in short order dinking around with extra hot loads, when you get flow it tends mess up the firing pin hole.

My smith has a special drill bit that he fixes firing pin holes with, he had to fix his own gun when the pin started sticking.

Coco, I don't think he's talking about an "impression".

In his post, "After 5k it's shown some deep round marked around the firing pin hole area."

That's gas blowback from around the primer, indicating that the primer didn't seal when fired.

An impression is one thing, erosion is another. If it can be felt with a pick (toothpick, etc.), then it's erosion, caused by gas blow by of the primer.

I color all of my brass with a red stripe, 1/4" wide, around the middle of the case. I can see this red ring inside my chamber, but it can't be felt. That's an impression.

[DyNo!]

I ran about 600 Fed SPM primers with 130PF loads and got some pretty bad erosion - use the softest primers you can...