Accuracy International Primer Flow

[trophyhunter]

How do I know that my AXMC needs to be bushed or just back out the firing pin ?

I'm running 6creed & 6SLR with 210m primers, I can not get any major speeds in any of my calibers without punching holes in primers. Once I start to get into some of the speeds with powder charges some people mention here I start to have major puckering on the primers with the occasional piercing. None of my rounds have experienced heavy bolt lift or had ejector marks on the brass, but I know AI's cover these symptoms easy with the design of the bolt that lift is not hard. Primers are not flat.

Another shooter in the local club matches advised me to pull the firing pin in a tad. So when my new firing pin arrives I will. The old pin had a nibble on it from piercing primers so another is on its way.

Any additional help or advice will be greatly appreciated.

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[Threadcutter308]

Looks to me like you have an uncomfortably hot load. The radius' on the primer cups are flattened and you have primer flow back into the firing pin hole. There could be much more going on here that I am not aware of, but this looks dangerous to me. I suppose it is possible the firing pin hole is too large (for the associated firing pin). If so, how it got that way may be a mystery.

 

[trophyhunter]

Since day one it's always cupped the primers, if I shoot Federal gold match in my 308 it'll do the same thing, not as much flowback but still noticeable.

Could this just be an issue with large firing pin ?


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[Supersubes]

I think pin size is irrelevant. Pin fit and profile are the main factors imo. Well, pressure too in any event. I see a pretty good ejector swipe on that second case up from the bottom. So you're up there with pressure.


What are your load details, barrel lengths, and velocities?

 

[trophyhunter]

That is 6SLR

24" Bartlein barrel

suppressed

115RBT DTAC

42.4 IMR4451

3012fps


The others are same but with 42.4 H4350, primers are much better, going 2968fps


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[lash]

Bushing for AI firing pins. Look it up. It's a thing, especially with .260, 6.5, 6, and etc.

 

[Citius7]

Change over to RL26. You will get the same speed and then some with less pressure. Give it a spin. You won't be disappointed.

 

[Jethro3898]

I have the same issue with my AIAX (2013 model) shooting factory Prime 6.5 ammo. The newest lot pierces primers probably 1-2 per box and EVERY primer is raised after firing. My first couple of cases of Prime functioned perfectly. Oddly enough, I lost about 15-20 FPS with the new lot, yet I have really been struggling with the primers piercing. Ammo groups just fine. We're talking factory ammo here, not hand loads. Admittedly, Prime is a little hot, but it still shouldn't do it this often.

As as a matter of fact, the last match I shot was 8 stages (1 day match) and I did not complete 2 of the stages due to a piece of a pierced primer getting in the bolt and not allowing the firing pin to hit the next round. It did it on one stage and I was able to pull the bolt, remove the body, clear the primer piece, and reassemble and finish the stage in time, but the other two stages I simply didn't have the time. The field serviceability of the bolt is really cool.....just not when you are under a 2 minute or 90 second time limit.

I've done the "turn the firing pin" thing once and it didn't do a thing. I'm going to try another half turn and see if that works, but the first one surely didn't.

If it it keeps doing it I will have no choice but to have the firing pin aperture bushed.....which I am loathe to do.

 

[trophyhunter]

Change over to RL26. You will get the same speed and then some with less pressure. Give it a spin. You won't be disappointed.

I'm game to try it, will post results

Any idea on powder charges starts ?


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[trophyhunter]

As as a matter of fact, the last match I shot was 8 stages (1 day match) and I did not complete 2 of the stages due to a piece of a pierced primer getting in the bolt and not allowing the firing pin to hit the next round. It did it on one stage and I was able to pull the bolt, remove the body, clear the primer piece, and reassemble and finish the stage in time, but the other two stages I simply didn't have the time. The field serviceability of the bolt is really cool.....just not when you are under a 2 minute or 90 second time limit.

If it it keeps doing it I will have no choice but to have the firing pin aperture bushed.....which I am loathe to do.

Ive done this exact thing at 2 of our last local club matches, I wasn't in the running for top 3 but it did cause me to lose by 1 point with my buddies that I'm always competing with, so he came in 9 & I got 10th. But that really puts a damper on my confidence not knowing if the shot will go off.

The downer is I'd have to do 3 bolts on my AXMC if I bush one of them.


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[NoLegs24]

The downer is I'd have to do 3 bolts on my AXMC if I bush one of them.


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Yeah, you'd have to bush them all. Or you can buy a new firing pin assembly and send it along with the 308 bolt body to Stuteville and have a dedicated small firing assembly/ bolt .....

 

[K_4c]

I went through this with my AXMC. I actually talked directly with AI's North American vp Scott S. Extremely nice guy.

Unfortunately, the only way to yield these results is to get it bushed.

AI firing pin measure .0785" and my 3 bolt body pin notes measured .083", .0835 and .086" (verified with certified pin gauges.

We talked a bit about primer shear strength and how the unsupported primer molds around the pin and in this case over comes the firing pin spring. My .300 Norma mag screwed up the tip of my original firing pin as well.

All that being said, your numbers seem slow for the charge weights. What chrono did you verify the posted speeds with?

make sure your not jamming the projectile into the lands, as that is only going to induce more pressure.

Virgin brass?

 

[trophyhunter]

This was all ran over a Magnetospeed V3


I'm currently running everything .020" off the lands.


Ya this is a pic of my current firing pin

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[Supersubes]

Wow, with that much gas cutting, the bolt fave and pin hole must have taken a hammering too. Bushing it may be your only option.

 

[trophyhunter]

That's what I'm afraid of, I wonder how much it would cost to bush 2 bolts & 1 firing pin ?


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[K_4c]

Wolf vs CCI primer... same load data. CCI have a soft cup.

 

[davidwiz]

That's what I'm afraid of, I wonder how much it would cost to bush 2 bolts & 1 firing pin ?

I think it's less than $300 to get an AI fp bushed. Stuteville Precision does it, among others. http://www.stutevilleprecision.com

 

[Citius7]

We run 42.2 grains of the RL 26 in 6mm lapua with 115 Berger and JLK. Going 3065 fps no pressure on a small rifle primer. Back off a grain and a half and I'd start there for u.

 

[SurgeonPredator]

Have the same with factory Lapua Lockbase cartridges on an old AWM .338LM. It's the "military" firing pin causing these imprints. Saw it on PGM rifles, too. Heard some even punch right through the primer on 6,5Creedmoor.

Started joking you won't need a primer. The pin will propel the projectile out the barrel on its own

My current loads show the same imprint on Federal 215 primers. Loads were measured at a proof house to be within CIP pressure specs. Clocked the load with maximum pressure of 420MPa and 913m/s v0 with RUAG cases, which usually are running hotter than Lapua brass.

97grs of N570, Lapua brass, 250grs Lockbase, 91.50mm COAL. Measured v0 with 913m/s on the Magnetospeed (will check more on Monday). The same load in a RUAG (SwissP) case clocks in at 928m/s. The AI suppressor increased the speed to 932m/s, but with huge SD increase. with the muzzle brake, the SD was just 2m/s.

Problem with the .338LM case is you won't see overpressure signs until 500MPa in some cases. The primers can be misleading though.

 

[Stevo3556]

I'm game to try it, will post results

Any idea on powder charges starts ?


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TrophyHunter,

What did you do about this issue?

I bought a new AXMC in 300 Norma and didn't have any pressure problems the first 100 rounds, started seeing them the next 50, then into the next 50, including a factory round, had primer punching and high pressure signs. Same load, nothing changed. Cleaned after each 50 rounds, no carbon ring.

Thanks,
Steve

 

[LRI]

To the OP:

We've bushed somewhere between 30-40 bolts now on the AI stuff and prolly a couple hundred worth of Rems, Rugers, etc... Judging from this photo it does not appear to me that you are experiencing elevated pressure. I base this off the following:

1. Absence of ejector marks on case heads
2. Radius feature of primer cup still present along the outer periphery

What I do see is a striker pin that is significantly smaller than the hole drilled into the face of the bolt head. The evidence of this is how the primer strike is extruded between the pin body and the ID of the hole in the bolt head.

This has been the achilles heel of the AI platform for a long time. One has to remember that the rifle was orginally designed for severe field duty anywhere in the world. Military ammuntion is fire and forget. They aren't policing brass and hosting reloading parties after a day of laying hate.

The photo of your striker pin suggests severe erosion at the business end. What I have done in the past to avoid the trouble of ordering a new one is just remove it, drill for a .062" pin, install a heat treated piece of drill rod, solder it, and reset the protrusion and contour. Thus far its worked pretty well. The comfort here is there's really nowhere to go but up. The striker is already %$^&@# so you really can't mess it up.

So, what to do? I can offer this: The process is covered in detail so be sure to review the listing if interested.

LRI Striker Pin Bushing Service

Here is what you can expect upon returning it:

We'd have your parts roughly 5 business days. Happy to help.

 

[6brshooter]

I'd send that to Chad and let him fix u up. Hes right on all points, that primer has very rounded edge still. Cci primers are a lot thicker cup than fed, I'd try those too.

 

[Jethro3898]

Chad (LRI) bushed the bolt on my AI and I have not had a single problem since. Turn around time was pretty quick.

Save yourself a lot of headaches and just shop him your bolt and a check.

 

[Mormegil87]

Following this.

 

[trophyhunter]

TrophyHunter,

What did you do about this issue?

I bought a new AXMC in 300 Norma and didn't have any pressure problems the first 100 rounds, started seeing them the next 50, then into the next 50, including a factory round, had primer punching and high pressure signs. Same load, nothing changed. Cleaned after each 50 rounds, no carbon ring.

Thanks,
Steve

What ammo brand are you running in 300norma?

From what I gather there is no standard on 300norma ammo, so pressure can vary causing primer flow. I had heard they were thinking of changing the AXMC to small pin to fix this issue for the PRS submission. I didn’t see a downside when I used my small pin in 300wm.

Chad @ Long Rifles did mine also, he’s done around 3 bolts for me, all AI’s.

 

[Stevo3556]

I shot Hornady 230gr Berger match ammo.

I

 

[tyfoon]

@trophyhunter

Happy I found this.

I have exactly the same (2020model AXMC shooting 300NM, 28" Bartlein barrel 1:8). Same effect as shown in the first post and today actually had 2 pierced primers. One with just 81.5GR N565 and one 84GR N565 (ELD-M 225GR projectile, 0,04 from the lands). @84 some very light bold lift but not other pressure signs.

How did you fix this in the end?

 

[trophyhunter]

@trophyhunter

Happy I found this.

I have exactly the same (2020model AXMC shooting 300NM, 28" Bartlein barrel 1:8). Same effect as shown in the first post and today actually had 2 pierced primers. One with just 81.5GR N565 and one 84GR N565 (ELD-M 225GR projectile, 0,04 from the lands). @84 some very light bold lift but not other pressure signs.

How did you fix this in the end?

If you’re getting bolt lift then you’re definitely in the pressure area, I’d address that as well. For primer pierce or flow they do make a small pin for the AXMC, need the firing pin and small pin bolt assembly. Or the alternative and way cheaper is having it bushed by a competent riflesmith.

 

[tyfoon]

If you’re getting bolt lift then you’re definitely in the pressure area, I’d address that as well. For primer pierce or flow they do make a small pin for the AXMC, need the firing pin and small pin bolt assembly. Or the alternative and way cheaper is having it bushed by a competent riflesmith.

Thanks.

I actually have complete AXMC bolts inc. firing pins; One complete with small pin (I use for 308 & 6.5CR) and one complete with large pin (I only use for 300nm). Are you saying I should try the small pin one in the 300nm bolt?

 

[trophyhunter]

Thanks.

I actually have complete AXMC bolts inc. firing pins; One complete with small pin (I use for 308 & 6.5CR) and one complete with large pin (I only use for 300nm). Are you saying I should try the small pin one in the 300nm bolt?

You’ll need the small firing pin and small hole bolt face for the 300nm for it to match.

 

[tyfoon]

If you’re getting bolt lift then you’re definitely in the pressure area

84gr n565 is near (but below) max recommended according to quickload. Not surprised I'm getting a bit of bolt lift there (but nothing more then a heave factory load). However 81.5 is far below max and still a pierced primer and had significant cratering below that.

Guess the best way forward is getting the bolt bushed.

 

[supercorndogs]

You should not be getting bolt lift with factory loads either. That is good indication something is wrong.