The long range AR-15 project

[6fatrat]

The 6 40 turbo or the 6 fatrat is the largest bolt face you want to run in a ar 15.
Proper cleaning and maintenance of your bolt and barrel extension is mandatory!
Wear your safety glasses.
Steve Bair

 

[yorke-1]

This is a blast from the past! LOL

I wouldn't dream of running over 40K psi on a SOCOM bolt in an AR. The 800 series bolt from ARP was capable of handling the pressure from the .473 bolt face wildcats based on the 6mm BR case at safe working pressures of that case, 52K psi.

I actually burned out both the 6.5 BRX and a 270 AR (270 Dasher) barrel on that rifle, both using the 800 Series bolt and extension, with no issues.

The 6 40 turbo or the 6 fatrat is the largest bolt face you want to run in a ar 15.
Proper cleaning and maintenance of your bolt and barrel extension is mandatory!
Wear your safety glasses.
Steve Bair

I'll just point out the obvious fact that you probably have a bias towards the Fatrat, given the fact that it's your screen name. LOL It's a great chambering too, and a better option now that the ARP bolts and extensions are unavailable.

 

[ARlife4me]

This thread is really old, but the "official" pressure limit for .458 socom is 35k psi, mostly due to how much material has to be hogged out of the bolt to fit the .308 sized case head, and still maintain the same approximate bolt lug stress as 5.56. No way I'd run anything near 65k psi in front of that thin bolt face.

There are other .473 bolt face out there other than for the socom. There is also bolts for wssm for AR15's. I have used standard 308 bolts in where other places state hp bolt required and have had several thousand rounds without any issues except for the firing pin (hp type and non). Bolt is the less of the issue! Example, with an AP barrel in 6.5Creed using standard rifle length gas system (I have 3 different barrel lengths) it has never had an issue with standard P bolt and pin. Faxon, cbi, pr and others that use standard and +2 gas system for the 6.5creed I have had lots of firing pin failures using hp and non bolts. I've tried titanium, steel and 1 other metal pin and all have failed miserably in 260rem, other 6.5creed and 243win. Again, 0 bolt issues! Gas rings could play a part in the 15 style, but haven't tested those yet. All have been tested with factory ammo from American manufacturers.

 

[WoodTRD]

There are other .473 bolt face out there other than for the socom. There is also bolts for wssm for AR15's. I have used standard 308 bolts in where other places state hp bolt required and have had several thousand rounds without any issues except for the firing pin (hp type and non). Bolt is the less of the issue! Example, with an AP barrel in 6.5Creed using standard rifle length gas system (I have 3 different barrel lengths) it has never had an issue with standard P bolt and pin. Faxon, cbi, pr and others that use standard and +2 gas system for the 6.5creed I have had lots of firing pin failures using hp and non bolts. I've tried titanium, steel and 1 other metal pin and all have failed miserably in 260rem, other 6.5creed and 243win. Again, 0 bolt issues! Gas rings could play a part in the 15 style, but haven't tested those yet. All have been tested with factory ammo from American manufacturers.

It's the shear stress on the bolt lugs that is the issue in an ar15 sized bolt with a .308 sized bolt face, not the firing pin or firing pin channel diameter. I looked into building a 300 WSM ar10, but, same issue. It can be done, but too close to the edge to try to hot rod or even come close to a bolt gun for me. When bolt lugs fail, it isn't pretty. Usually no/minor injury with AR pattern rifles with eye protection, but...not something I relish experiencing.

 

[ARlife4me]

With the same barrel length it's difficult to get the same velocity as it is out of a bolt gun. Usually 50fps or less depending on the cartridge.