Help with firing pin

db2000

db2000

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Minuteman
    • Mar 27, 2020
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    #1
    My Seekins AR10 firing pin seems to get very dirty quickly shooting 25CM suppressed. It was cratering 210M primers also. I bought a V Seven titanium pin and it broke off in several primers today. Not sure what’s causing this. Any help appreciated.
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    #3
    msgriff said:
    Can you accurately measure the bolt face firing pin orifice? It would also help to have the firing pin tip diameter, measured at around 0.050" from the end, if you can remove it from the primer.
    Click to expand...
    I can give it a shot with my Mitutoyo’s.

    Additional info should include I don’t have any issues with the same BCG and same primers in my .308 upper with Varget and Bergers or in 8.6 Blk upper with 300gr SMK and A1680. All Seekins. The 25CM upper did not always crater primers. I didn’t change reloading formula just seemed like it started one trip to the range, prompting buying the new firing pin after reading that may be the issue.
     
    #5
    Rocketvapor said:
    You sure that's the pin and not the primer anvil blown through the cup?
    View attachment 8335615
    Click to expand...
    I bet you’re correct. It doesn’t make sense that 4 cases all look the same (just like your picture) because there couldn’t be enough metal lost from the firing pin to leave that much metal in every primer. It would be too short to even make it through the bolt orifice. Is that from a pierced primer?
     
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    #7
    Check the gas port for buildup.
    Notice that the case in my pic, the dreaded 22 Nolser, doesn't show signs of pressure other that the pierced primer. Gas port stripped some copper from 88 ELDs and little pressure spike from bullet hitting port blew primer. Did a few before I noticed brass.
     
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    #8
    I checked gas ports and they’re open. The firing pin does seem to take on a lot of fouling with 25CM making its movement sticky compared to 8.6 Blk and .308 uppers I use the BCG in also. Cleaning everything causes less cratering and it gets worse the longer I shoot. The only change I’ve made from initially shooting the upper when it was first built was adjusting the SA AGB from bleed off to open a few full rotations as the brass was ejecting at 1 o’clock initially. May I added to much gas coming back. I’ll play with that.

    Any additional thoughts appreciated.
     
    #10
    PusherX11 said:
    What was temps at the range today? Were these the first 4 fired?
    Click to expand...
    These were shot a few months ago. About 50-60 rds in on a new McGowan barrel. Maybe 60F max but likely colder as it’s winter in VA. Similar to other rounds. Same load and Lapua brass. Also tried new Alpha srp 25CM specific brass. Similar result without the metal sticking out. Deep craters though
     
    #11
    PusherX11 said:
    What was temps at the range today? Were these the first 4 fired?
    Click to expand...
    Did it again today and it was 83F 57% humidity. To reiterate the same BCG/bolt, now a new firing pin, works fine with .308 SP10 upper and 8.6 BLK SP10 upper (super and subs). I hope someone can shed some light on this.
     
    #13
    Try closing your gas block completely and shoot suppressed, and unsuppressed.

    Does this occur unsuppressed?

    Try some cci 34s, they will have a thicker cup then the 210m, Remington 9 1/2s.
     
    #14
    PusherX11 said:
    Try closing your gas block completely and shoot suppressed, and unsuppressed.

    Does this occur unsuppressed?

    Try some cci 34s, they will have a thicker cup then the 210m, Remington 9 1/2s.
    Click to expand...
    I did adjust the block down and feel like it didn’t cycle. Also made various open adjustments until cycling suppressed but honestly don’t remember if it affected the primers. It does occur unsuppressed also. The thing is, this gun ran fine without this happening for 50 or so rounds. I didn’t change powder or other variables. I did change firing pins because the original got chewed up at the tip from this process. There’s a pic above of that I believe. Just very strange and I figured surely someone on here would have the answer. I appreciate the tips and may have to change primer. Just doesn’t make sense how it started suddenly
     
    #15
    Are you using a HP bolt typically found in 6.5 CM AR10s? If not, that is likely your fix.
    It explains why it doesn't happen in your 308 and it's exactly what happens in many 6.5 CM AR10s (or even some bolt guns) that have the firing pin hole that's too large for the cartridge.
     
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    #16
    srt-4_uk said:
    Are you using a HP bolt typically found in 6.5 CM AR10s? If not, that is likely your fix.
    It explains why it doesn't happen in your 308 and it's exactly what happens in many 6.5 CM AR10s (or even some bolt guns) that have the firing pin hole that's too large for the cartridge.
    Click to expand...
    Ahhh. I did get a new BCG from Seekins and I bet I didn’t put the original JP HP bolt in that carrier. That’s been a while ago but who know. I’ll look. Thanks

    Edit. I am still using the JP HP Enhances bolt in the Seekins carrier. Firing pin 0.0580” at tip.
     
    Last edited:
    #17
    msgriff said:
    Can you accurately measure the bolt face firing pin orifice? It would also help to have the firing pin tip diameter, measured at around 0.050" from the end, if you can remove it from the primer.
    Click to expand...
    0.0580” at the tip. It’s got some carbon fouling although I wiped it down. Maybe that’s the 0.008”
     
    #18
    db2000 said:
    Ahhh. I did get a new BCG from Seekins and I bet I didn’t put the original JP HP bolt in that carrier. That’s been a while ago but who know. I’ll look. Thanks

    Edit. I am still using the JP HP Enhances bolt in the Seekins carrier. Firing pin 0.0580” at tip.
    Click to expand...
    Did you modify the firing pin? V7 doesn't list a TI firing pin for the small firing pin hole.
     
    #19
    srt-4_uk said:
    Did you modify the firing pin? V7 doesn't list a TI firing pin for the small firing pin hole.
    Click to expand...
    I did not.
    But the one I measured, is the one I’m currently using. Seekins firing pin.
    The V7 got chewed up at the tip when this all started. That’s the picture above probably. I’m still having the issue even after changing the firing pin.
     
    #20
    The Seekins or V7 never would have been able to protrude and hit the primer if the bolt had the small firing pin opening. The JP HP bolt comes with its own firing pin because of this.
    Id double check to make sure you have the JP HP bolt or just the JP enhanced.
     
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    #23
    srt-4_uk said:
    The Seekins or V7 never would have been able to protrude and hit the primer if the bolt had the small firing pin opening. The JP HP bolt comes with its own firing pin because of this.
    Id double check to make sure you have the JP HP bolt or just the JP enhanced.
    Click to expand...
    I found the order in my email from 2021. It is a JP enhanced bolt and not HP Enhanced. I didn’t realize at the time. Thanks. I’ll start there by getting a proper one and proper JP HP enhanced pin. Also, several engineers at Federal are stumped and said they’ve never seen the anvil come through like this. They have requested the used cases and old titanium V7 pin to evaluate. I thought that was pretty nice of them.

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    #24
    Well, put in a new Seekins bolt carrier and JP HP bolt and firing pin combo.
    First round was great. Every round after, light primer strikes. Jeez.
    I’ll try this bolt/firing pin with my previous Seekins carrier and see what happens.
    I haven’t changed any other variables.
    IMG_6512.jpeg
     
    #25
    Next time you try it, give your forward assist a tap before you pull the trigger and see if that makes a difference. The majority of the time light strikes are caused by the carrier not going forward enough which means the bolt is not fully locked up.
    The fix there is more lube on the carrier, working in those gas rings, different mag, or stronger buffer spring.
     
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    #26
    H2 or H3 buffer will help light primer strikes. You could be experiencing bolt bounce where the carrier will bounce off the face of the barrel extension just enough to cause a light primer strike. An H2 or H3 buffer will provide enough weight to alleviate this.
     
    #27
    PusherX11 said:
    H2 or H3 buffer will help light primer strikes. You could be experiencing bolt bounce where the carrier will bounce off the face of the barrel extension just enough to cause a light primer strike. An H2 or H3 buffer will provide enough weight to alleviate this.
    Click to expand...
    I’ve got a Tubbs flat spring and 5.6oz KAK wt. There is no “forward assist” on the Seekins SP10. I can manually assist by pushing forward on the side of the bcg though. I’ll try that before swapping the bolt into the old Seekins carrier. Thanks
     
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    #29
    db2000 said:
    I’ve got a Tubbs flat spring and 5.6oz KAK wt. There is no “forward assist” on the Seekins SP10. I can manually assist by pushing forward on the side of the bcg though. I’ll try that before swapping the bolt into the old Seekins carrier. Thanks
    Click to expand...
    Get rid of the flat spring and your bolt will start going all the way into battery. I’m convinced they are inferior to conventional springs.
     
    #30
    I don’t know if it’s possible but is there a chance your barrel is now broke in and has sped up putting your load on the hotter side of things? Just curious because you said it started after 50-60 rounds.
     
    #32
    Also, after reading the rest of the thread, you have at least two ejector marks on your case head (post 24). Honestly, it looks like three.
    How hot is that load?

    Have you also checked firing pin protrusion? If it's too long, that could explain the piercing of the primers.
     
    #33
    Mike Casselton said:
    Also, after reading the rest of the thread, you have at least two ejector marks on your case head (post 24). Honestly, it looks like three.
    How hot is that load?

    Have you also checked firing pin protrusion? If it's too long, that could explain the piercing of the primers.
    Click to expand...
    Some loads got too hot initially, 42.0 of H4350 and Berger 133. I scaled back to 40.0 and still got pierced primers until changing to the high pressure bolt and different Seekins carrier. Now this happened. Not sure it matters but for what it’s worth this new carrier has 3 gas ports and prior that I used with the non-high pressure JP bolt had 2. Seekins rep says they’ve used a few different carriers over time.
    The new HP JP bolt has its own HP pin. The prior may have been too long but that’s old news now.
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    #35
    I feel the primers are seated ok. Haven’t rechecked head space with the new bolt but barrel was installed professionally but my smith I’ve used for years and checked initially with the other JP bolt, which I realize doesn’t matter now potentially.
    I appreciate the help.
    IMG_6582.jpeg
     
    #36
    srt-4_uk said:
    Next time you try it, give your forward assist a tap before you pull the trigger and see if that makes a difference. The majority of the time light strikes are caused by the carrier not going forward enough which means the bolt is not fully locked up.
    The fix there is more lube on the carrier, working in those gas rings, different mag, or stronger buffer spring.
    Click to expand...
    So, this was the issue. Noticed the carrier not al the way forward and I could physically move it back and forth 1/8” or so.
    Then noticed the buffer was not coming all the way forward to the detent pin. It was catching on some metal that had somehow created a catch.
    Also then the pin had sheared down as well so replacing that and the buffer tube.
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    #37
    Check your buffer/tube/spring combo. Something isn't right length-wise and is allowing your carrier to travel too far into the tube. The deformation circled is the carrier's bearing surface contacting the lower. Its likely what caused that burr the buffer caught on. It can also destroy your bolt catch over time because the BCG and buffer have more forward momentum before the bolt catch stops it.

    Typically it's caused by mismatched buffer/buffer tube or a buffer that has a stop that's deformed or broken down.

    20240825_184209.jpg
     
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    #38
    srt-4_uk said:
    Check your buffer/tube/spring combo. Something isn't right length-wise and is allowing your carrier to travel too far into the tube. The deformation circled is the carrier's bearing surface contacting the lower. Its likely what caused that burr the buffer caught on. It can also destroy your bolt catch over time because the BCG and buffer have more forward momentum before the bolt catch stops it.

    Typically it's caused by mismatched buffer/buffer tube or a buffer that has a stop that's deformed or broken down.

    View attachment 8487641
    Click to expand...
    Thanks for the info. It’s almost certainly the 2.5” KVP 5.6 oz buffer in an A2 rifle tube. For carbine I see now. 🤦‍♂️
     
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