Pierced Primer Question: AI AX and Prime 107 Grain 6mm Creedmoor

jab00

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I need some help with trying to figure out what may be going on with my 2018 AI AX and factory Prime Ammo 6mm Creedmoor. Any advice or guidance would be appreciated:

Background:
  • 2018 AX with a 24" Proof stainless steel 6mm Creedmoor barrel (24")
  • Factory Prime Ammunition 107 grain 6mm Creedmoor rounds
  • Over the past couple of range trips with this ammo (all from the same lot), I've experience several deep primers strikes that are almost to the point of piercing, along with some more normal looking primer strikes with what looks like minor cratering but no real evidence of ejector swipe
  • During today's range trip, I had 3 rounds out of 20 fired that had deep primer strikes and two that actually punctured the primer cup (I could see light through the primer when I held the round up towards the light). I stopped at that point to avoid doing any damage to my bolt face or firing pin
  • I've previously fired both factory Hornady and Federal Gold Medal Match 6mm Creedmoor rounds through this barrel and have never noticed any of the above issues (although I wasn't looking that closely at each spend round like I have been with the Prime Ammo after I noticed the first deep hit while I was cleaning up my brass
  • I've also fired factory .308 Win , .260 Remington, and 6.5 Creedmoor with this rifle, using factory AI barrels, and have never noticed any obvious pressure signs at all using a variety of ammo brands and weights (175s, 168s, 140s, 120s)
  • I'll try to post some pictures of the primers as soon as I can
So here are my complete novice-level questions:
  • Does Prime Ammunition tend to load their rounds towards the "hot" end of the scale and it just may be too much for my particular barrel chamber?
  • Is it possible that the pressure level of these rounds is okay and I just need to have my firing pin bushed (not sure if that's a thing with AI rifles). I would think that I would see deep primer strikes and/or cratering on the other calibers that I'm shooting through this particular rifle if this was truly the cast; however, I'm not knowledgeable to know if that is truly the case
 

jab00

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Here’s some pictures of the primers. I decapod the deep strike primers and one was fully pierced and the other two were slightly pierced

 

Lucky Se7en

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I'm sure there are things that you could do to troubleshoot this but based on my experience and reading other threads on here, I feel like you will need your firing pin bushed to solve this. This is assuming you have the large diameter firing pin...I am pretty sure short action AX's were being sold with smaller diameter firing pins over the last few years but I'm sure someone else here could give you exactly when.

I had asked a similar question in the past about my AE MKIII in another thread and also spoke on the phone with AINA...when everything was said and done I sent my bolt in to have the firing pin bushed and have not had a pierced primer since. I imagine that the pressures and primer cup thicknesses of some manufacturers cause issues...I would mainly shoot 308 FGMM which was always fine but about 1/3 of the Lapua ammo I'd shoot would have a primer pierced.
 
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jab00

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This is a 2018 model so it would have the small pin. I actually just measured my pin to be certain and it’s the SFP. However, maybe I still may need to bush it depending if I notice that it’s doing the same thing with other calibers/brands. I can’t say for certain that this wasn’t happening with Hornady and FGMM 6mm but never noticed the issue until I started with Prime.

ETA: I had bit of a battle getting my bolt disassembled to do the measurement of the pin. There were some pieces of primer in there that were apparently preventing me from getting the safety lever to the middle position to take the spring tension off
 

jab00

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You probably need to adjust the firing pin protrusion.
Are there instructions on how do this in case I go that route? I did some internet searching and couldn't find anything.

I took the rifle back out this morning with my .308 barrel and some 168 FGMM and the primer strikes on all 40 rounds looked perfectly normal. I'm thinking that I may want to put the 6mm barrel back on next weekend and take a box of Hornady and FGMM 6mm and see if the primers look normal or the deep strikes/piercing reappears. I didn't notice this problem with those two brands before (after shooting a box or two) but maybe I just didn't notice (I only realized that I was having a problem with Prime when I happened to pick up a random piece of brass and saw the deep hole). If those primer strikes look normal, then I think I can safely say that the Prime ammo won't work for me in this gun.
 

Huskydriver

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Are there instructions on how do this in case I go that route? I did some internet searching and couldn't find anything.

I took the rifle back out this morning with my .308 barrel and some 168 FGMM and the primer strikes on all 40 rounds looked perfectly normal. I'm thinking that I may want to put the 6mm barrel back on next weekend and take a box of Hornady and FGMM 6mm and see if the primers look normal or the deep strikes/piercing reappears. I didn't notice this problem with those two brands before (after shooting a box or two) but maybe I just didn't notice (I only realized that I was having a problem with Prime when I happened to pick up a random piece of brass and saw the deep hole). If those primer strikes look normal, then I think I can safely say that the Prime ammo won't work for me in this gun.

Measure the protrusion and report back. There are basically only two settings on a AI firing pin.

Should be between .055-.075 iirm
 

FCS

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Powder used in PRIME ammo isn’t compatible with your rifle.
Plenty of radius on primer, first glance this isn’t a peak pressure issue.
Could be a primer cup issue (thickness, material, etc.)
Picture 1, 3 (right side, closest) & 5 (right side, closest) shows protrusion of primer back into firing pin hole of bolt.

Best guesstimate I have with information available is burn rate is a little on quick side.
PRIME, along with most manufacturers at the moment, are limited on propellant choices.

What is velocity of PRIME vs Hornady or Fed?
 

samb300

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    Are there instructions on how do this in case I go that route? I did some internet searching and couldn't find anything.

    I took the rifle back out this morning with my .308 barrel and some 168 FGMM and the primer strikes on all 40 rounds looked perfectly normal. I'm thinking that I may want to put the 6mm barrel back on next weekend and take a box of Hornady and FGMM 6mm and see if the primers look normal or the deep strikes/piercing reappears. I didn't notice this problem with those two brands before (after shooting a box or two) but maybe I just didn't notice (I only realized that I was having a problem with Prime when I happened to pick up a random piece of brass and saw the deep hole). If those primer strikes look normal, then I think I can safely say that the Prime ammo won't work for me in this gun.
    See post #39
    https://www.snipershide.com/shootin...ing-pin-bushing-service-for-ai-rifles.201722/
     

    jab00

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    Powder used in PRIME ammo isn’t compatible with your rifle.
    Plenty of radius on primer, first glance this isn’t a peak pressure issue.
    Could be a primer cup issue (thickness, material, etc.)
    Picture 1, 3 (right side, closest) & 5 (right side, closest) shows protrusion of primer back into firing pin hole of bolt.

    Best guesstimate I have with information available is burn rate is a little on quick side.
    PRIME, along with most manufacturers at the moment, are limited on propellant choices.

    What is velocity of PRIME vs Hornady or Fed?

    A) Prime says 3051 fps
    B) Hornady says 2960 fps
    C) Federal says 3000 fps

    To be honest, I’ve never had the chance to chronograph any of these with this barrel so those numbers are strictly from the box.
     

    Huskydriver

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    Just buy a Non-gay rifle.

    I use a Savage. Never had that issue.

    im 100% hits on an IPSC at a mile with my 30’06.
    Old IOR 2-12 in Warne vertical split rings.
    Caldwell bipod.
    tenor.gif
     

    Rthur

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    Unless AI has changed their specs on firing pin to bolt clearance this is an old side effect.
    Used to see this on 6.5x47 srp.
    Can show on LR as well.
    Built in tolerance for extreme conditions this rifle is fielded in.

    R
     
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    Nik H

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    So here are my complete novice-level questions:
    • Does Prime Ammunition tend to load their rounds towards the "hot" end of the scale and it just may be too much for my particular barrel chamber?
    • Is it possible that the pressure level of these rounds is okay and I just need to have my firing pin bushed (not sure if that's a thing with AI rifles). I would think that I would see deep primer strikes and/or cratering on the other calibers that I'm shooting through this particular rifle if this was truly the cast; however, I'm not knowledgeable to know if that is truly the case
    My thoughts
    1. I have fired a LOT of PRIME ammo in different calibers and have never seen it be hot. Not saying that it can't happen. I just don't have any experience with this caliber though.
    2. If your AI is 2018, then the firing pin issue that was causing cratering with small rifle primers isn't it. The new firing pin diameter went into production in 2015 on all AI rifles to the best of my knowledge.
    3. Have you called Mile High Shooting and asked them what may be going on?
    Good luck and let us know what you find out.
     

    spife7980

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    I’ve had one batch of prime and it was really hot. Left ejector marks on damn near every case resulting loose primer pockets for its second loading.

    That said, since you have the small firing pin already: clean your barrel.
     
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    jab00

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    My thoughts
    1. I have fired a LOT of PRIME ammo in different calibers and have never seen it be hot. Not saying that it can't happen. I just don't have any experience with this caliber though.
    2. If your AI is 2018, then the firing pin issue that was causing cratering with small rifle primers isn't it. The new firing pin diameter went into production in 2015 on all AI rifles to the best of my knowledge.
    3. Have you called Mile High Shooting and asked them what may be going on?
    Good luck and let us know what you find out.

    Thanks - I actually did try to reach out to MIle High on Saturday afternoon but they must of been busy since I couldn’t reach anyone. I was going to try again tomorrow to see what they say

    ETA: I’m also going to try and reach out to Prime too
     
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    jab00

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    I’ve had one batch of prime and it was really hot. Left ejector marks on damn near every case resulting loose primer pockets for its second loading.

    That said, since you have the small firing pin already: clean your barrel.

    Someone yesterday at the range had mentioned the possibility of a dirty chamber/barrel possibly causing the issue but it was cleaned after my last trip so it was pretty spotless when the problem started yesterday. The only thing that I haven’t done is really scrub the chamber since the overall round count is pretty low (~300 rounds total). I could definitely do a deep clean of the chamber and barrel before the next trip
     

    spife7980

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    If you don’t have a bore scope to actually check your cleaning: Do a couple patches of clr and let it sit wet in the bore for 20 minutes and then clean it like you normally would to flush the clr out. The clr will really go after any hard carbon immediately but don’t let it sit for hours in end or get on any other metal you don’t want stripped clean though just to be safe.

    Today I just did a few clr patches on a rl16 shot barrel I cleaned normally and they came out foamy immediately, the clr was going to town on all the hard carbon still left behind right away. Didn’t take long to get really clean.
     

    jab00

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    If you don’t have a bore scope to actually check your cleaning: Do a couple patches of clr and let it sit wet in the bore for 20 minutes and then clean it like you normally would to flush the clr out. The clr will really go after any hard carbon immediately but don’t let it sit for hours in end or get on any other metal you don’t want stripped clean though just to be safe.

    Today I just did a few clr patches on a rl16 shot barrel I cleaned normally and they came out foamy immediately, the clr was going to town on all the hard carbon still left behind right away. Didn’t take long to get really clean.

    I do actually have a bore scope and not sure why it didn’t occur to me to take a look at the chamber. I’ll try that tomorrow and see what it looks like in there.
     

    mercracing

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    I’ve shot a good bit of Prime in 260, 6CM, and 338LM. Both the 260, and 6CM were very hot. I pierced primers in 260 in my AXMC, but that was with a LFP. I ordered the small pin and my problems went away.
     
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