AI Small Firing Pin (Planning on shooting 6.5 CM)

The Durk

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Hey everyone!

I'm a little over halfway saved up, to purchase a new 20" AI AT rifle in 308. It seems like the model I want only comes with the large firing pin, and I'd have to buy a small firing pin bolt, separately. I'm planning on reloading 6.5CM, and buying a barrel, to go along with the 20" 308 that comes stock. Do I really need a small firing pin, or am I just overthinking the issue?
 

Aaron47pb

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Not sure where you're looking, but ATs come in small firing pin and in 6.5 Creedmoor. Buy what you want. Give Mile High Shooting a call.
 

W54/XM-388

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I would suggest you call up Mile High AND Euro Optic both and see what they can do for you price wise on a New or Demo AI AT rifle in 6.5 Creedmoor with the small firing pin bolt & the barrel length you want.

Then if you want .308 as well, just look around here on the hide for someone selling a .308 barrel cheap. They come up all the time for prices way lower than 6.5cm barrels sell for.

That would wind up saving you some money.
 

b6graham

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you're gonna want a small firing pin.

but like everyone else said. buy it in 6.5 Creed with the small pin, and find the 308 barrel elsewhere
 

milanuk

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Okay... I'm going to tag onto this, if that's okay. If not, point me to the right place (different thread, forum, etc.).

I'm familiar with the problems associated with having too large of a firing pin *hole* in the bolt, relative to the firing pin itself, and how that can be addressed by bushing the hole, reaming a new hole and turning the pin to fit with minimal clearance (how minimal depends on the usage - BR vs. field, etc.)

I'm getting the impression that y'all are talking about something else, with the tip of the pin itself being too big somehow w/ regards to small primers? What am I missing here?
 

b6graham

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Okay... I'm going to tag onto this, if that's okay. If not, point me to the right place (different thread, forum, etc.).

I'm familiar with the problems associated with having too large of a firing pin *hole* in the bolt, relative to the firing pin itself, and how that can be addressed by bushing the hole, reaming a new hole and turning the pin to fit with minimal clearance (how minimal depends on the usage - BR vs. field, etc.)

I'm getting the impression that y'all are talking about something else, with the tip of the pin itself being too big somehow w/ regards to small primers? What am I missing here?
big hole/primer with small primers in higher pressure rounds can lead to cratering, blowing primers, and flow back into the big hole
 

milanuk

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So essentially the same thing as I was talking about... just apparently you can order an AI with a small pin/hole out of the box, like a lot of other custom actions?
 

spife7980

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So essentially the same thing as I was talking about... just apparently you can order an AI with a small pin/hole out of the box, like a lot of other custom actions?
F=P/A

F= the "oomph" pushing on the primer
P= Pressure in the case
A=area of the primer


If we are guessing 60k psi round that leaves us with 60,000/5 (random number for large primer area)=12,000 psi
If we were to go with a small primer that is 60,000/2.5 (half the random number to signify smaller primer. )=24,000 psi

The small primer putting more pressure on the unsupported firing pin will exceed the primer cups ability to hold up to the pressure made during firing and puncture. The larger firing pin leaves more of the primer unsupported by the bolt face so you go with a small firing pin, the primer cup cant push through the solid bolt face material around a small pin.


They just all come small firing pin now. You can use it for large and small primers
Even on the AXMC? I thought those big bolts were still going with the large pin, I could very well be (and probably am) wrong on that though.
 

W54/XM-388

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Even on the AXMC? I thought those big bolts were still going with the large pin, I could very well be (and probably am) wrong on that though.
The AXMC line ship with the standard large firing pins.
I'm assuming you could have the bolt / firing pin bushed.
 

Muldoon7

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Check out eurooptic I just bought the same rifle with small firing pin from them new at a great price. You should be able to find exactly what your looking for at the same price.
 

n2stcks

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I shoot 6.5 CM factory loads with a large firing pin and have had no problems. It is a 2014 large pin 308 AX just before they changed over to the small pin. YMMV
 
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The Durk

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You guys have all been a tremendous help! Thank you! I'm starting to reload, which is why I want something like 308, to cut my teeth on. It has a far longer barrel life than 6.5, and allows me more testing before I get good load data, and learn what I'm doing. Mid 2019 I'll be purchasing a Proof carbon fiber barrel in 6.5.
 

nexusfire

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You guys have all been a tremendous help! Thank you! I'm starting to reload, which is why I want something like 308, to cut my teeth on. It has a far longer barrel life than 6.5, and allows me more testing before I get good load data, and learn what I'm doing. Mid 2019 I'll be purchasing a Proof carbon fiber barrel in 6.5.
If you really do the math, it will take you a lot longer to shoot out a 6.5 barrel then you think. The average person will get 3-5 years from one. If you religiously shoot 100 rounds a month it would take you about 2 years. I have had my 6.5 for about 2 years and I have about 1300 rounds on it.
 

Aaron47pb

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If you really do the math, it will take you a lot longer to shoot out a 6.5 barrel then you think. The average person will get 3-5 years from one. If you religiously shoot 100 rounds a month it would take you about 2 years. I have had my 6.5 for about 2 years and I have about 1300 rounds on it.
Some wisdom right here.
 

The Durk

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I on average shoot 200-300 rounds of 308 a month, besides the winter months, where I normally only shoot about 40-100 rounds a month. Mainly because my R700P doesn’t like to work in the cold.

I have several 5 gallon buckets filled with Federal Gold Metal Match brass. I’ll probably have enough brass to hold me over for 4-6 years.

Don’t even get me started on my carbines. My SBR is on its 3rd upper, and it’s 5 years old.

Thanks for all the advice!