What Diameter Blank to Order For an AR15?

[ridgeway]

I want to replace my Mil spec M4 contour barrel with a nice quality blank without breaking the bank. I plan on going with X-Caliber and have them turn down a 28" blank. I was wondering, should I have them turn down to .980"? I believe this is pretty much the OD of an AR barrel?

I have a Wylde reamer, go gauge and a BAT barrel extension. I plan on making it straight taper to a mid length or rifle length gas block and run a .936" gas block. Looking at doing a 18" to 20" barrel.

 

[akajun]

I would suggest a Green Mountian Blank in the 1.0" diameter so you have less that you have to turn off. I have built several Space Gun and Service Rifle barrels with their blanks and they are all hammers.

BTW, you dont need a blank bigger than 1" as that is about as big as will pass through the barrel nut. I usually leave everything under the handguard the full 1" unturned diameter, then on space guns, a .936 diameter for a bout 2". then about .925 to then end of the barrel and or turn and thread the muzzle if required.

Caution though, make sure you have whatever gas block you are going to use in hand and measure it before you turn the area for the block. The .936 diameter is not as standardized as the .750 the Military uses. Some blocks will be .937.

 

[ridgeway]

Thanks for the info...

As for Green Mountain. I don't see any 1" stainless blanks on their website. Do they offer them? I was planning on an 8 twist to shoot the 77 SMK's, but only see chromoly. I guess I could always coat it...

 

[ridgeway]

Also, would you go with a rifle or mid length gas port? If so, what diameter gas port?

 

[akajun]

What overall length barrel? If Rifle length, then rifle length of course and .092-.096 diameter. I personally like to get my gas system as far away from my chamber as possible to increase dwell time and lower port pressures. The closer you get to the chamber, the smaller the gas port is, I think a 16" calls for a .067 or so, but you can find the standard dimensions on the net.

I prefer the 1/7 for my purposes as I shoot berger 82's at 600 and they absolutly hammer the 77's as well. If you want to do a 1/8 that would probably be fine. here's the 1/7's I use

http://www.gmriflebarrel.com/bxs223-7-223-cal-1-7-twist-stainless-barrel-blank/?page_context=category&faceted_search=0

If you want a 1/8 stainless, here is one, but its 1.250 Dia
http://www.gmriflebarrel.com/rxs228-223-stainless-1-8-twist-barrel-blank/?page_context=category&faceted_search=0

 

[akajun]

One other thing, do not get too tight with your bolt to barrel clearance, I like to use a .007" clearance and heaspace a little on the loose side, say .002-3 past the go gauge.

 

[ridgeway]

Thanks for the help and all the tips, much appreciated.

Also, thanks for the link. I may just order one and give it a try. I have a bunch of 77 SMK's and that is why I want something that will shoot them. The 7 twist should do just fine.

Have you measured any of your barrels to see if they are truly a 7 twist?

How do they look inside? Clean up pretty nice?

I will probably end up going with 18" or 20" barrel length. In 223, I doubt there is much difference?

As for the go gauge, I have a forster 223. I'm guessing it will work fine for the Wylde chamber? I don't see any reason it won't. I do know PTG makes one that is labeled Wylde, but it has to be the same as 223.

The reamer I have is several years old, 2005. The FB on it is .025 with a 1* 30 leade. I made a stub/headspace gauge with it and soft seated a bullet. Seems like the 77's will be close to being able to mag feed seated on the lands. I know this is not a true and accurate way of finding zero, but its pretty close to what the chamber will be.

 

[SDWhirlwind]

Probably more than you want to spend but heck, it is only money and you would have the best or close!

http://www.bullets.com/products/-224-5R-1-7-7-Twist-26-Finished-1-050-Straight-Barrel/T10735

 

[ridgeway]

Probably more than you want to spend but heck, it is only money and you would have the best or close!

http://www.bullets.com/products/-224-5R-1-7-7-Twist-26-Finished-1-050-Straight-Barrel/T10735

SD...thanks for the link. That sure would be a nice barrel for sure! That's a bit much I want to spend to put into an AR.

 

[akajun]

Your headspace gauge should be fine.
Load your 77's to 2.260 max
They like a little jump.
No I have never actually checked the twist rate on any of my barrels, but they all seem to shoot well.,

 

[ridgeway]

Got it all finished and its ready to test out!

The barrel machined very nice! Hopefully it shoots as good as it looks.