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Thread: m1 carbine piercing primers

  1. #1
    Boolit Master sixpointfive's Avatar
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    m1 carbine piercing primers

    Never had a problem with this usgi m1 carbine. But today it is piercing primers. I noticed that firing pin protrusion is excessive. I just wonder why all of a sudden. Can I just grind a bit off of the firing pin?

  2. #2
    Boolit Master

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    Far better to disassemble the bolt and clean the firing pin channel, pin, and spring. Probably some crud inside the bolt causing the pin to stick forward. Instructions for disassembly of the bolt can be found in many publications. The military used a special tool, which is also available for purchase, but if you study it a bit you can do it without the tool.

  3. #3
    Boolit Master
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    Don't grind on the firing pin!! It's been a while since I had a m1 carbine apart. But something has broken to let the firing pin stick out that much. Carefully disassemble the bolt and compare the parts to the appropriate TO manual. You will find something wrong.

  4. #4
    Boolit Master
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    What primers are you using, and has that changed any? Just a longshot ...

  5. #5
    Boolit Master sixpointfive's Avatar
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    I took the bolt apart. Everything looks good. I do not see any wear or broken parts. All I can see is excessive firing pin protrusion

  6. #6
    Boolit Master

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    Well, speaking as one who owns 5 of them and others in the past, I can assure you that the firing pins don't grow. So if everything is fine inside the bolt, and if you've not experienced the problem in the past, then one would have to next examine the ammunition being used. I once had a large supply of surplus French-made .45 ACP ammo that seemed loaded unusually hot. Almost every round had a pieced primer after firing, whereas other ammo did not. You really want to try to isolate the source of the problem, because removed metal is kind of final, and if you then fire some other ammo and it won't discharge you will have to replace the firing pin. As noted by Kestrel4k (above) the primer is a good place to start. Are you firing reloads? Is the ammo surplus? Since you experienced your problem, have you tried some commercial rounds; or if the commercial rounds are the ones causing the problem, have you tried a different brand?

    All that having been said, sometimes parts wear and that fact easily escapes the normal level of examination. I once had a .45 Auto that pierced primers (not the situation already mentioned) and found it to be a burr in the firing pin hole in the face of the slide. This, in turn, roughened up the firing pin a bit so the two were eating each other, and the burrs caused the firing pin to stick forward, but the discharge would usually drive the pin back inside the slide, so it was hard to detect and figure out. The cure was to highly polish the firing pin and to take a round needle file and rotate it a few times in the firing pin hole in the slide face. Not scrubbing it back and forth---rotating--and just a few turns, not enough to enlarge the hole. You might try this fix. Could be that a burr has developed in the hole in the face of your bolt, and the firing pin may have become correspondingly rough. Good luck with this.

  7. #7
    Boolit Master Outpost75's Avatar
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    Do you have a depth mic or gage to measure the driven protrusion of the firing pin, or are you just eyeballing it and making a judgement?

    I don't recall what the protrusion spec. is for the M1 carbine, but on the M16 and M4 it is 0.028-0.032" so the carbine should be close to that.
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  8. #8
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    My Inland has been piercing primers lately too, with LC ammo. I guess it's time to strip the bolt down and give it a thorough cleaning. Thanks for the reminder.


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  9. #9
    Boolit Master sixpointfive's Avatar
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    I stripped the bolt, nothing seems to be worn or damaged. Perhaps it's the primer type I bought. I have so many different brands and it's been a while since I reloaded I do not know which ones were used.

    What are you looking for when you strip yours down?

  10. #10
    Boolit Master
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    Quote Originally Posted by sixpointfive View Post
    I stripped the bolt, nothing seems to be worn or damaged. Perhaps it's the primer type I bought. I have so many different brands and it's been a while since I reloaded I do not know which ones were used. [...]
    I'm thinking it's S&B primers or similar weak cups - which is what we've been asking about since yesterday.
    Last edited by Kestrel4k; 06-27-2017 at 06:12 PM.

  11. #11
    Boolit Master
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    Have you checked the tip of the firing pin to see if it got gas cut from the pierced primers?. Had this happened in a 6.5 Swedish mauser with some old Lapua match ammunition. Cost me a new firing pin and did check the firing pin protrusion with the tail end of a good set of dial calipers. Frank

  12. #12
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    I mentioned previously in this thread that my M1 Carbine is piercing primers with LC ammo. I checked my firing pin over the holiday weekend, an it does indeed have a chip in the side of it. Not sure how that happened, but I ordered a new firing pin from Fulton Armory. I'm hoping it will just drop in and be good to go, or do I need to be concerned about checking protrusion?

  13. #13
    Boolit Master Outpost75's Avatar
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    Quote Originally Posted by ShooterAZ View Post
    I mentioned previously in this thread that my M1 Carbine is piercing primers with LC ammo. I checked my firing pin over the holiday weekend, an it does indeed have a chip in the side of it. Not sure how that happened, but I ordered a new firing pin from Fulton Armory. I'm hoping it will just drop in and be good to go, or do I need to be concerned about checking protrusion?
    If replacement part is USGI, ir "should" drop in with no issues, but it is ALWAYS a good idea to measure or gage and check.
    If you have an M16 protrusion gage:

    http://www.brownells.com/gunsmith-to...prod26477.aspx

    I would use that, it should fit into the carbine boltface.

    I see they are using 0.036" max. now, used to be 0.032 back in my time.
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  14. #14
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    Thanks Outpost, I'll check it.

  15. #15
    Boolit Master
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    Think of escaping gas from the pierced primer like a steam leak. I've seen steam valves that had a flange leak so bad new gaskets wouldn't help. Only solution was to replace the valve. I had this happen with a Swedish mauser and some older Lapua berdan primed ammo. Didn't notice the first pierced primer, but sure did the second one. Replaced firing pin and double checked the firing pin protrusion. Think once you get the new pin you should check the protrusion and you should be ok. I've seen a rem 700 that was badly chewed up due to pierced primers. Guy almost had a stroke after I took the bolt and removed the firing pin assembly and tapped it on a wood bench and watched all the little discs form the pierced primers. Frank

  16. #16
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    Ok, follow up. I received my new firing pin from Fulton Armory (old one was chipped and piercing my primers). So last night after an hour and a half, and a couple gouges and blood blisters on my fingers I got it replaced.This is a job that takes about four extra hands to do, with no room for any of them. The good news is that I took it out this morning and test fired it and it functions perfectly. No pierced primers, nice rounded indents.

  17. #17
    Boolit Master
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    Love it when a fix works. Frank

  18. #18
    Boolit Master
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    I always advise that anyone taking apart a carbine bolt get a bolt tool. It is worth the cost. You could have done the job in less than 5 minutes and not risked loosing any parts. And little or no swearing!!!!

  19. #19
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    Yes sir, lots of swearing indeed. If I ever have to do it again I will get the tool. I have done Garands and M1A bolts so I thought I could tackle it. Certainly not easy to do.


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  20. #20
    Boolit Master


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    I learned a long time ago the simply holding the bolt in a vise works best. That frees up one hand to push the ejector in with a punch and the other to snap the extractor into place with ejector pushing in and aligned correctly. Still, it can be a hassle.
    Larry Gibson

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BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
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GC Gas Check