Interest in firing pin bushing service for AI rifles

[Known]

All,

I would like to ascertain the level of interest in a firing pin bushing service for Accuracy International (AI) rifles. AI does not provide this service and I am not aware of anybody in the US providing such a service for AI rifles. It is my understanding that this service is only available through a gunsmith in the UK complicating matters for AI owners in the US and other geographies.

To enhance the reliability of their rifles, AI uses a larger firing pin compared to other rifles such as a Remington 700. The larger firing pin aperture increases the likelihood of primer piercing particularly with 6.5mm cartridges. Currently, AI will not bush firing pins or provide the option of a smaller aperture bolt face with their 6.5mm offerings.

I have approached Accuracy International and they have politely declined to offer such a modification. While I don't agree with them, this is their right and I respect that. Unfortunately, this leaves me (and other shooters based on postings I've seen) unable to shoot cartridges like the .260 Remington at competitive velocities (2800fps with a 139 Scenar out of a 26" barrel). There are so many things I like about my AIAW that I am willing to go this route as a last resort before moving to a custom platform.

By understanding the demand, I am hoping that Accuracy International will change their mind and provide the option of a narrower firing pin aperture and/or bush firing pins for current owners. Also, folks like GreTan will believe it worth while to expand their current firing pin bushing service to AI rifles.

Please indicate your interest by replying to this thread. If you are successfully shooting 6.5MM calibers without piercing please share your load data. In my case I have seen piercing with CCI BR2 and CCI 200 primers when using 42gr of H4350 and above with Lapua .260 brass and 139 Scenar.

Thank you for your time.

 

[Straight Shooter]

Stipulations in owning an AI rifle are:

Not to use custom, hand loaded, reloaded, ammunition.

No unauthorized adjustments, alterations, repairs or modifications.

This is easy. Just sell it to someone that only shoots factory ammo and have a custom built.

 

[sib1948]

Just purchased a new AI AXMC and plan to use it mostly in 243 and 260. Hopefully, I won't have any issue, since I don't plan to use extremely hot loads. I would be interested to get more information on the primer piercing issue! Thanks

 

[AEROMechanic]

Just purchased a new AI AXMC and plan to use it mostly in 243 and 260. Hopefully, I won't have any issue, since I don't plan to use extremely hot loads. I would be interested to get more information on the primer piercing issue! Thanks

You'll be fine, there are a bunch of people who handload in the aforementioned calibers with little to no issues..

 

[sib1948]

You'll be fine, there are a bunch of people who handload in the aforementioned calibers with little to no issues..

Thanks. That makes me feel better. It is what it is! We'll see once I can starting putting some lead down range.

 

[Eagle1899]

My AX has never seen factory ammo. No problems what so ever.

 

[bward]

Bushing them isn't a problem. Not sure why most of the gunsmiths won't. If you used a fitted bushing and carbide tooling its just like any other job. My 6.5x47 AW is bushed.

 

[SRSDriver]

I had a different brand of gun that had a factory bushing that fell out, resulting in good times. I don't get primer peircing, I wouldn't mess with it at all. One more thing to fall out to fix a problem I've never had.

 

[poison123]

Weird......I've shot 6mm Crusader, 6mm Creedmore, .260 Rem all through 26" barrels on AWs and AX's and Never Not Once Pierced or had a single problem.

Granted I've only used good primers like Wolf or Fed210m.

 

[Known]

My AX has never seen factory ammo. No problems what so ever.

Weird......I've shot 6mm Crusader, 6mm Creedmore, .260 Rem all through 26" barrels on AWs and AX's and Never Not Once Pierced or had a single problem.

Granted I've only used good primers like Wolf or Fed210m.

Could you please share the load data. I'm particularly interested in .260.

 

[poison123]

Could you please share the load data. I'm particularly interested in .260.

Keep in mind this is on a GAP chambered Barrel.

42gr of H4350
142 SMK
2.80" OAL
Rem Brass
Fed210m

Averaged about 1/3 moa when I still shot 5 rnd groups with it.

 

[Known]

Stipulations in owning an AI rifle are:

Not to use custom, hand loaded, reloaded, ammunition.

No unauthorized adjustments, alterations, repairs or modifications.

This is easy. Just sell it to someone that only shoots factory ammo and have a custom built.

Believe me, that thought has occurred to me.

 

[Known]

I had a different brand of gun that had a factory bushing that fell out, resulting in good times. I don't get primer peircing, I wouldn't mess with it at all. One more thing to fall out to fix a problem I've never had.

And for that very reason I would like to see AI come out with a narrow aperture bolt face from the factory. I would be the first in line.

 

[poison123]

I'm just curious have you seen this piercing of the primers with factory fresh brass? Or is it after you've sized it?

 

[Known]

I'm just curious have you seen this piercing of the primers with factory fresh brass? Or is it after you've sized it?

I have experienced this issue with virgin and fired brass. When I resize I bump the shoulder back about .001 - .002. As a result my resized brass is about .003 longer than virgin brass as measured from the shoulder with an RCBS case micrometer. I also trim with a Giraud case trimmer .005 below maximum.

As far as other details are concerned, I use a .292 redding bushing and am .030 off the lands. I weigh every charge with an RCBS Chargemaster.

 

[matt2143]

I have fired about 160 rounds total of four different lots of 6.5 Creedmoor Factory 140 AMAX ammo through a 23.6" and 20" barrel and just pierced a primer on the 20" last time out. I have always had flow back with the AX even in .308.

So far I shot 45-50 rounds through the 23.6" with CCI BR2, H4350 (from 43-45.2 grains) 140 Berger Hybrid loaded to 2.938" overall and never pierced one. i also shot 55 rounds of 43.3 grains of the same load through my 20" without a single problem.....

Although I have heard of this issue, until the factory round the other day I never had a problem personally. We will see if I do begin to have issues after I find a new load for the 20" tomorrow.

 

[Eagle1899]

I am not running a 260.

But I do push a 175BTHP out of a 20" 308win barrel at 2750 with no problems. I think it has a lot to do with headspace control. Over sizing brass, jamming bullets into the lands, pressure spikes, soft primer cups, all play into pierced primers.....

 

[Pusher591]

I have fired about 160 rounds total of four different lots of 6.5 Creedmoor Factory 140 AMAX ammo through a 23.6" and 20" barrel and just pierced a primer on the 20" last time out. I have always had flow back with the AX even in .308.

So far I shot 45-50 rounds through the 23.6" with CCI BR2, H4350 (from 43-45.2 grains) 140 Berger Hybrid loaded to 2.938" overall and never pierced one. i also shot 55 rounds of 43.3 grains of the same load through my 20" without a single problem.....

Although I have heard of this issue, until the factory round the other day I never had a problem personally. We will see if I do begin to have issues after I find a new load for the 20" tomorrow.

What were your velocities with that 23.6" barrel and for what charge?

 

[matt2143]

45.2 grains @ 2910 from a 23.6" Bartlein 1-8 5r. Chambered in 6.5 Creedmoor

 

[Known]

I have been told that carbon or copper buildup could be contributing to my primer piercing. Using my Hawkeye bore scope I cleaned the barrel down to bare metal. I had to use JB and Kroil to get everything out.

Today I went to the range and had a pierced primer after 50 rounds using 42gr H4350, Lapua .260 brass, CCI BR2, and 139 scenar .030 off the lands. This load chronographed at 2750fps.

I'm going to drop down to Zak Smith's published load of 40.7gr H4350. I will have to live with 139 Scenars going at 2,700 fps for now.

 

[bward]

If you aren't blowing primers with that it isn't going to happen. That is extremely hot. Has to be close to 80k psi.

45.2 grains @ 2910 from a 23.6" Bartlein 1-8 5r. Chambered in 6.5 Creedmoor

 

[Hoser]

I am pushing 115 DTACs out of my 6CM around 3,000 fps and dont have any problems.

So far everything I have put through my PSR has been good as well.

 

[Brasscow]

Both my AXs crater primers pretty bad with mild to moderate loads. I'd be interested in this.

 

[Pusher591]

You think the new MC versions will have these problems as well? Was seriously thinking about selling my custom to get a new AXMC but now I'm not so sure.

 

[Known]

You think the new MC versions will have these problems as well? Was seriously thinking about selling my custom to get a new AXMC but now I'm not so sure.

If you stick to .308 I doubt you'll have a problem. I only started to experience the problem when I moved to .260. You might want to go to AI and ask if the firing pin aperture on these rifles will be smaller.

 

[bm11]

I've had two different experiences on this subject. My first was with my 2007 AIAW when I spun a 6.5x47 barrel on it. It pierced a primer if I looked at it funny, to the point where the barrel/rifle combo was unusable. Even with mild/starting loads it would pierce 50% or more of the primers, so that barrel came off in a hurry.

My other experience is with my AIAX (2010 action, or is it a '09?) I have run hot to nuclear loads in both .243 and .260, without ever having an issue. In one instance, and I hate to admit this, I accidentally loaded H4895 into my charge master when I should have loaded in H4350, so I ended up with 42.5 grains of H4895 under a 140 Berger Hybrid, and didn't realize it until my cold bore impact was a full mil high at 600 yards. No pierced primers.

My personal conclusion with this? While small rifle primer calibers like 6.5x47 Lapua may be an issue, I would certainly run .260 or 6.5 Creed before determining you HAVE to bush the bolt. Because you'll probably be just fine.

 

[cruizer]

Send it to gre tan rifles. He turns bolt around really quick

 

[Known]

Send it to gre tan rifles. He turns bolt around really quick

I contacted him yesterday and received the following response: "It is case hardened & not tool steel. So I do not do them."

 

[Known]

I've had two different experiences on this subject. My first was with my 2007 AIAW when I spun a 6.5x47 barrel on it. It pierced a primer if I looked at it funny, to the point where the barrel/rifle combo was unusable. Even with mild/starting loads it would pierce 50% or more of the primers, so that barrel came off in a hurry.

My other experience is with my AIAX (2010 action, or is it a '09?) I have run hot to nuclear loads in both .243 and .260, without ever having an issue. In one instance, and I hate to admit this, I accidentally loaded H4895 into my charge master when I should have loaded in H4350, so I ended up with 42.5 grains of H4895 under a 140 Berger Hybrid, and didn't realize it until my cold bore impact was a full mil high at 600 yards. No pierced primers.

My personal conclusion with this? While small rifle primer calipers like 6.5x47 Lapua may be an issue, I would certainly run .260 or 6.5 Creed before determining you HAVE to bush the bolt. Because you'll probably be just fine.

Just on this thread alone we have folks who can run hot loads without an issue and others who have problems with mild loads and factory ammo. I spoke with one of the AI distributors and they wonder if it might be a tolerance stacking issue. They cited one client with two rifles. One bolt pierces primers on a regular basis and the other doesn't. As a result, this customer just uses a particular bolt between rifles.

I spoke with another owner who said that reducing the firing pin protrusion as outlined in the armorers manual could help, but may cause problems with factory ammo that is sized to minimum headspace. I'm going to look around and see if I can find the manual so I can experiment.

 

[samnev]

Just a thought. CCI #34 primers are mil spec and harder than regular CCI primers or BR 2 primers.So perhaps instead of using BR 2 primers the harder #34 primers might not pierce.

 

[Niles Coyote]

[MENTION=14488]Known[/MENTION] be sure to post your outcome, I am considering a AT and would be running a 260 barrel as well

 

[Known]

Just a thought. CCI #34 primers are mil spec and harder than regular CCI primers or BR 2 primers.So perhaps instead of using BR 2 primers the harder #34 primers might not pierce.

I contacted CCI directly about this. CCI BR2 and CCI #34 have the same cup thickness - it's what they call their "thick cup". CCI #34 is a magnum primer and the anvil is different to make it less sensitive.

I also learned this: While CCI 200 and BR2 can be used interchangeably, CCI 200 has a thinner cup than the BR2. As a result, I switched to BR2 but I still get piercing.

The CCI rep would not supply the actual cup measurements since they are considering proprietary. He also confirmed that the measurements floating around on the internet for CCI primers are not correct.

 

[Known]

[MENTION=14488]Known[/MENTION] be sure to post your outcome, I am considering a AT and would be running a 260 barrel as well

I'll certainly do that. As a potential customer you might have more leverage over AI if you called them up and inquired about a modified firing pin aperture.

You might get lucky and fall into the group of AI users who can run even hot loads without a problem. On the other hand, you might be in my group where you will be left to your own devices. As we can see from the post above, even factory loads can pierce.

I have also heard directly from an AI owner who has experienced piercing with factory .308 loads. While I have not experienced piercing with my .308 loads (43gr Varget with 175 SMK and Lapua brass) I did experience some cratering with BR2 primers.

To keep everything in perspective, if you do have a pierced primer all you have to do is disassemble the bolt and dump out the small round bit of metal from the primer cup. This may not help you in a match though. To AI's credit, the trigger will not take a dump as often happens with Remington rifles. Also, it's a snap to disassemble the bolt - so much easier than a Remington 700.

 

[matt2143]

I just shot my 20" 6.5 Creedmoor barrel today. Ran up to 45.7 grains in .3 grain increments, after 44.8 grains I did not increases velocity or change POI at 300 yards. There was FAINT ejector swipes at 45.1 on two of the cases, none on the 45.4 or 45.7. Getting 2840 from a 20"! Needless to say total I fired 90 rounds today with zero pierced primers.

 

[bward]

I just shot my 20" 6.5 Creedmoor barrel today. Ran up to 45.7 grains in .3 grain increments, after 44.8 grains I did not increases velocity or change POI at 300 yards. There was FAINT ejector swipes at 45.1 on two of the cases, none on the 45.4 or 45.7. Getting 2840 from a 20"! Needless to say total I fired 90 rounds today with zero pierced primers.

How many firing on the brass? I would be really surprised if the pockets last more than 2-3 firings at those pressures.

 

[matt2143]

2 so far. Gunna run them again this weekend. We will see how it holds up. I'm good with 3-4 firings, then I'll move on to more virgin brass and start again.

 

[mattwaage1]

In my TRG vs AW quest this came up, and is why I went with the TRG, along with price and weight. Though the new AT has me thinking about adding that to the safe. Do post the findings of the firing pin size of the AT if anyone learns.

Sent from my C811 4G using Tapatalk

 

[Supersubes]

Something I have never seen anyone mention is the odd pin profile the AW uses. It is large in diameter, has a large radius face, and sharp edges where the face meets the shaft. Compare this to a Remington.

I have Remington's that have large gaps between the pin and hole, and produce donut shaped craters with any load, but don't pierce. I think this issue is caused by a combination of factors, including pin profile and pin protrusion. I pierced a few primers several years ago, and have seen a few near pierced primers. They are distinct in that they look like very uniform extrusions, not the crusty cratering produced by the average hot loaded Remington.

To make a long story longer, my rifle was back at AINA for a trigger repair and they found my pin protrusion was out of spec. Not sure whether it was too much or too little, but I suspect it was too much. Post fix, my primer strikes look absolutely perfect. I'll try to post some pics later. My rifle has a 27" .260 barrel chambered by a buddy. Load is 130 jlk's, 44gr h4350, in WIN 7-08 necked brass. 2900 fps

 

[Known]

All,

I figured out how to adjust the firing pin protrusion between information that I received from Lowlight via PM and another source. I searched around and couldn't find directions, so I'll supply them here. The setup that AI has is really quite elegant. I'm told this procedure is outlined in the armorers manual which I would like to get my hands on. We'll see if this addresses my issue. Along with any unauthorized adjustment to the rifle, you perform this at your own risk.

There are two set screws (one of top of the other) in the cocking piece. They take the same size wrench. The longer pointed one goes in first.

The firing pin is threaded through the cocking piece and you can turn it to adjust the protrusion. You can turn it by placing your fingers as shown. Half a turn will adjust protrusion by approx .010 - 0.012. You can remove the firing pin entirely by simply screwing it out. By removing the firing pin you will understand how the set screws work and why you have to adjust it half a turn at a time. In addition, you can't turn the firing pin more than one full turn past the factory setting or else the set screws will not work properly. You'll understand what I mean when you take it apart and examine it.

I took two pieces of virgin Lapua brass, primed them with CCI BR2 primers, and then fired them. There was NO powder or bullet. The cartridge on the bottom represents the factory setting. The one of the top represents one half turn of the firing pin inward. It's hard to see in the photo, but the factory setting really stretches the primer cup almost cutting into it where the tip radius meets the shaft. The adjusted setting looks more than adequate. If I turn the firing pin another half turn inward the primer will not fire.

I wanted to make sure that the reduced protrusion would not cause ignition problems. I took primers and seated them hard to the point they were flattened out and were .010 - .012 below flush. I used virgin brass which is set to minimum headspace. It fired using a CCI BR2 and a CCI #34 which is considered a less sensitive military grade primer.

I do not know which setting meets factory specs and AI will not share this information. That's their right. To their credit, they said they would examine the bolt and adjust protrusion. Personally, it's nice to have the flexibility of making these adjustments in the future.

Update: I found out from a well informed source who shall remain anonymous that the firing pin protrusion spec is .042 - .058. When you take the measurement make sure the bolt shroud is hanging in the air and not pressed up against a table.

 

[matt2143]

Wow good info Known. I'll do that test tonight and see if it changes what my primers look like this weekend.

 

[Lowlight]

I told you guys... spin the firing pin I said, still nobody listens, I guess I needed pictures.

 

[Known]

Wow good info Known. I'll do that test tonight and see if it changes what my primers look like this weekend.

Next up I'll provide a pictorial on how to adjust the trigger as I have not seen one after searching around. By adjusting the first stage only, you can get a kick ass 2.5lb two stage trigger (1lb first stage and 1.5lb second stage). I did not play with the second stage (sear adjustment) for obvious reasons.

If you plan to encounter arctic or very dirty conditions you can set the first stage back to factory specs (2.5lb) as the extra weight will push through any accumulated ice/crud.

 

[Ring]

Stipulations in owning an AI rifle are:

Not to use custom, hand loaded, reloaded, ammunition.

No unauthorized adjustments, alterations, repairs or modifications.

This is easy. Just sell it to someone that only shoots factory ammo and have a custom built.

guess what... it will do it with factory ammo....

 

[Ring]

Just a thought. CCI #34 primers are mil spec and harder than regular CCI primers or BR 2 primers.So perhaps instead of using BR 2 primers the harder #34 primers might not pierce.

cci 34's are the same as cci mag, the mag cost much less....

 

[Ring]

All,

I figured out how to adjust the firing pin protrusion between information that I received from Lowlight via PM and another source. I searched around and couldn't find directions, so I'll supply them here. The setup that AI has is really quite elegant. I'm told this procedure is outlined in the armorers manual which I would like to get my hands on. We'll see if this addresses my issue. Along with any unauthorized adjustment to the rifle, you perform this at your own risk.

There are two set screws (one of top of the other) in the cocking piece. They take the same size wrench. The longer pointed one goes in first.

The firing pin is threaded through the cocking piece and you can turn it to adjust the protrusion. You can turn it by placing your fingers as shown. Half a turn will adjust protrusion by approx .010 - 0.012. You can remove the firing pin entirely by simply screwing it out. By removing the firing pin you will understand how the set screws work and why you have to adjust it half a turn at a time. In addition, you can't turn the firing pin more than one full turn past the factory setting or else the set screws will not work properly. You'll understand what I mean when you take it apart and examine it.

I took two pieces of virgin Lapua brass, primed them with CCI BR2 primers, and then fired them. There was NO powder or bullet. The cartridge on the bottom represents the factory setting. The one of the top represents one half turn of the firing pin inward. It's hard to see in the photo, but the factory setting really stretches the primer cup almost cutting into it where the tip radius meets the shaft. The adjusted setting looks more than adequate. If I turn the firing pin another half turn inward the primer will not fire.

I wanted to make sure that the reduced protrusion would not cause ignition problems. I took primers and seated them hard to the point they were flattened out and were .010 - .012 below flush. I used virgin brass which is set to minimum headspace. It fired using a CCI BR2 and a CCI #34 which is considered a less sensitive military grade primer.

I do not know which setting meets factory specs and AI will not share this information. That's their right. To their credit, they said they would examine the bolt and adjust protrusion. Personally, it's nice to have the flexibility of making these adjustments in the future.

will try..
this was my issue with REM primers,

and a bit better with CCI 200, but still not perfect

 

[Known]

I found out from a well informed source who shall remain anonymous that the firing pin protrusion spec is .042 - .058. When you take the measurement make sure the bolt shroud is hanging in the air and not pressed up against a table. I will update my original post with this information.

 

[Straight Shooter]

I didn't know the protrusion was even a question. All center fire rifles run about the same range. .050 to .063 is a good range to stay in. You can experiment with your own. Have you tried magnum primers? I am constantly surprised by how many people avoid them. I use them in everything. 22-250 through Chey Tac. I don't even own a standard primer anymore.

 

[Known]

I didn't know the protrusion was even a question. All center fire rifles run about the same range. .050 to .063 is a good range to stay in. You can experiment with your own. Have you tried magnum primers? I am constantly surprised by how many people avoid them. I use them in everything. 22-250 through Chey Tac. I don't even own a standard primer anymore.

Hi,

I spoke with the folks at CCI and they told me that their BR2 primers have the same cup thickness as their magnum and #34 primers. For that reason I've never been compelled to use the magnums. I've got a bunch of the #34 (which are magnum mil spec primers) so I could give them a try.

I believe most folks use a standard primer because milder primers are considered more accurate and give lower SD.

 

[Known]

I contacted Warner Tool Company and they are willing to bush the firing pin: Warner Tool Company Alan Warner suggested bushing the bolt only to reduce firing pin clearance to .001. Need to think that one over as I had planned to have it turned down to .068. Alan's suggestion would allow me to replace a broken firing pin without having to turn it down. I'm sure he knows a lot more than me when it comes to this sort of thing.

I also found this interesting - read the 7th paragraph:

Problems with Primers | Shooting Illustrated

 

[Ring]

I contacted Warner Tool Company and they are willing to bush the firing pin: Warner Tool Company Alan Warner suggested bushing the bolt only to reduce firing pin clearance to .001. Need to think that one as I had planned to have it turned down to .068. Alan's suggestion would allow me to replace a broken firing pin without having to turn it down.

I also found this interesting - read the 7th paragraph:

Problems with Primers | Shooting Illustrated

Price?

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