Made an impulse buy on an ai at and don't know much about them... I know mine has a folder and the switch barrel system. I've been reading about large vs the new small firing pins. When did they start making with the small firing pins? How will I be able to tell which one I have? Is there anything else I should look for? I won't be home for another two months so until then I won't be able to get hands on info on the rifle. Thanks.
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Ai at small vs large firing pins
- Thread starter jeffl838
- Start date
I believe they started making the small firing pin ATs in late 2015, so that would be a clue based on your serial number (15AT vs 16AT). The best bet is to ask the seller if he knows, or have someone pull the bolt and firing pin and measure. I believe the small firing pin is approximately 0.062" dia., while the large firing pin is approximately 0.080". The firing pin mechanism is very easy (and tool free) to remove from the bolt body, so maybe you can get someone mechanically inclined to measure it for you while you're away from home.
Will you be primarily shooting small primer calibers like 6.5x47L or the new Lapua 6.5 Creedmoor brass? If not, you don't really need to worry about the large firing pin if you will be shooting regular large rifle primer calibers.
Will you be primarily shooting small primer calibers like 6.5x47L or the new Lapua 6.5 Creedmoor brass? If not, you don't really need to worry about the large firing pin if you will be shooting regular large rifle primer calibers.
That's correct, only needed if you are shooting something with a small rifle primer like a 6.5x47L or the new Lapua 6.5CM.
Someone mentioned to me that you can somehow "shortened" the length of the fp on the AT to prevent primer piercing on the small fp cartridges without having to get the bolt bushed?
Here is a link to the instructions. Credit goes to a SH member but I can't remember who it was.
ETA: If the member sees this let me know so I can give you credit!
https://www.dropbox.com/s/ncnbmuopkg...usion.pdf?dl=0
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The picatinny adapter that samb300 makes to replace the spigot mount is the best thing I have ever purchased for an AI
Beyond that just read the manual and get out there and shoot.
There are many guys shooting small primers with regular sized firing pins without any issues what so ever so it's entirely up to you. If you're. It going to be using small primers, which it sounds like you're not, then no need to worry.
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If he uses Lapua brass for the 6.5CM he will be using small primers. In the end getting the SFP is cheap insurance that you will be happy with your rifle for years to come. If I was buying used I would pay a couple hundred dollars more for a SFP version just because I may want/need it eventually.
I'm using the new Lapua brass with a regular size pin and have had zero issues. Like I said, if you want piece of mind then go ahead but it's not that big of a deal. This topic has actually been discussed several times in different threads recently ever since the new Lapua brass came out and there are tons of people shooting them with regular pins.
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I had an AIAW and have a AIAT, neither of them could shoot x47L without piercing primers. Had bolt bushed by Stuteville and its all good now.
Did you buy it new? I just bought a new 16AT from MHSA and it has the small firing pin. I think its the only option now or at least the way it comes without specifying otherwise.
Get the small firing pin.
I have an AIAW and it will only shoot .308. Every time I tried to get it to run with my 260 barrels it will pierce primers at any kind of useful velocity. It needs to be bushed down to a smaller diameter to run with these higher pressure calibers. The 260 is a large primer caliber, but it still pierces primers.
If you get the small firing pin from the beginning you will avoid a lot of headaches later. There's a reason why AI ships with the small firing pin option now so take advantage of it.
I have an AIAW and it will only shoot .308. Every time I tried to get it to run with my 260 barrels it will pierce primers at any kind of useful velocity. It needs to be bushed down to a smaller diameter to run with these higher pressure calibers. The 260 is a large primer caliber, but it still pierces primers.
If you get the small firing pin from the beginning you will avoid a lot of headaches later. There's a reason why AI ships with the small firing pin option now so take advantage of it.
If it is not a SFP you can also send it out and have it bushed. IIRC its only $200-300. You could always ask someone to pull the bolt and ship it out to get bushed. If it doesn't need it, you would just be out shipping but ready to go when you get back.
Does the small firing pin also work fine for large primers like .308 and Hornady 6.5 Creedmoor ammo?
Is this something that only affects AIAT owners or also AXMC owners?
Is this something that only affects AIAT owners or also AXMC owners?
Yes, it will work fine on large primers.
I havent heard of the MC's doing it. Just all the smaller framed guns that preceded it (AW, AX, AT)
Hmm... then why don't they just make the small firing pin the standard and only offering for the AIAT?
No, it has zero to do with AI guns and everything to do with shooting large rifle brass like 6.5x47L or .308 Palma brass with SRP, or 6.5CM Lapua brass with SRP. It is the large FP hitting a SRP. In fact, I was shooting with a buddy just today who was shooting a new 6.5x47L (non-AI rifle) who was having pierced primer like crazy...
My AXMC does it when I get into any pressure or higher velocity calibers. My 6 creedmoor & 6SLR are punching through primers. I pulled the firing pin .012" back and it still punches through. It'll do it with factory 6 creedmoor on a hot day. My 308 Federal Gold has a nice crater, you can set a fired case on glass and watch it wobble on the primer.
Currently I'm on my 3rd firing pin, at $85 a pop it's getting to be annoying.
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Currently I'm on my 3rd firing pin, at $85 a pop it's getting to be annoying.
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I have a couple 6.5x47L barrels,,2 cases on left are from my Stiller Tac 30 Bartlien 8 twist bbl,,,the 2 center cases are from a factory 700 PSS with an 8 twist Brux,,2 cases on right are from same 700 PSS Brux after getting the bolt bushed and firing pin turned by Greg Tannell from Gre-Tan Rifles,,the loads are all the same,,130 VLDs with 42.8 grs H4350 and CCI 450 primers
not true...and like ive posted in every one of these posts about AI pins for the past couple years, its dependent of each specific bolt, firing pin, and barrel...some have issues even with factory 6.5 creed ammo and very mild 6/6.5 loads with large rifle primers...see enough AIs and youll see some that are picky...shortening the firing pin protrusion (usually fixes it), changing primers (sometimes can help), and turning down the pin/bushing the bolt (fixes it for good) are ways to work around it if a bolt has issues
the cause for the pierced primers in any rifle AI or otherwise is the clearance of the hole in the bolt face and the firing pin itself,,if the hole is sloppy and there is play with the firing pin you will pierce primers with pretty mild loads,,if the firing pin is snug in the hole you will stick cases in the chamber before piercing a primer with way over max loads,,
I have a couple 6.5x47L barrels,,2 cases on left are from my Stiller Tac 30 Bartlien 8 twist bbl,,,the 2 center cases are from a factory 700 PSS with an 8 twist Brux,,2 cases on right are from same 700 PSS Brux after getting the bolt bushed and firing pin turned by Greg Tannell from Gre-Tan Rifles,,the loads are all the same,,130 VLDs with 42.8 grs H4350 and CCI 450 primers
The bolt face scrubbing on these cases is severe. Are you a neck sizer by chance? Also, that charge in my guns would be appropriate for a 6.5 creedmoor, not a 47 lapua.
I am sure that load is on the hot side but the cases had well over 20 reloads on them and still have tight primer pockets ,the first 100 cases actually put over 3,000 rounds on the Tac 30 and that is where that rifle shot the best and the magnetospeed showed 2950 fps with ES under 10 and SD`s of 3-4 for 10 shot strings,,the primers arent overly flat and the bolt opens smooth and easy,,but I did drop down to 41.0 for the Rem action rifle,,
Hmm... If I have a long action AXMC but shoot 6.5 Creedmoor, am I going to have problems using the new Lapua 6.5 Creedmoor small primer brass?
Depends on how hot you run it, but most def will. I was piercing primers shooting the factory PRIME 130's. Turning the firing pin back half a turn helped. But those use large primers.
That's extremely disappointing. It's funny how I went from an AIAT to a AXMC and am now seriously contemplating going back down to a AIAT lol.
Or you can just buy a new firing pins assembly to have that bushed with the 308 bolt body and have a complete dedicated SFP assembly
Thats a small pin for sure. A standard pin is around .080. If your caliper is that far out, fix it or toss it. Lol
They are Mitutoyo IP67's, $200+ digital calipers, I doubt they are far off lol. Im just curious as to how this older pre-2014 AX (has AT style LH folding stock) came to have the newer 2015+ small firing pin?
Is there a headspace discrepancy between AI rifles with a SFP and one with a LFP? Seems like there was some discussion on that a while ago with guys having issues with head spacing with aftermarket prefit barrels when the SFP rifles first came out. Can anyone clarify this?
Awesome! Did he tell you how much he had to shave off the boltface or if it would affect head space at all? Can you PM me what he charged for the service?
Honestly, I don't remember. You should probably just give him a call. He did a great job and haven't pierced a primer since with my 6XC barrel.
