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DPMS Pattern in 7MM-08

RPGesus

Private
Minuteman
Jul 26, 2020
25
9
I'm putting together a large frame AR in 7mm-08, and I think I prefer the 20" barrel for this build. Does anyone have experience with gas port sizes/buffer systems for such a build? I can't find any information that I deem reliable for this caliber. I need to get it right the first time, as I can't afford to tinker with a bunch of parts/gunsmithing later on. Thanks
 
This sounds like an interesting project. I don't really have all of the answers you're looking for, but here are a few of my thoughts...

First, a 7mm08 (which I love) is trading commonality (the 308) for some ballistic advantage. So unless you're really going to go balls out for precision, I'd stick with 308.

Second, assuming that the first thought doesn't matter because you've made up your mind, I would double down on quality. If you're taking the time to build an LR308 use really good components. I'd certainly go full-length gas tube. Also, there's no more deserving recipient of an adjustable gas block than what you're doing. It's a crap shoot, so make it adjustable. Kick-ass barrel is required, otherwise what's the use? Same with a trigger.

I'll assume you're shooting heavy bullets in 7mm08, so the standard 308 buffer should work just fine.

I own an LR-308 in 308, and it's a great rifle. Someday I'm going to geek out on it more. For now I just love it for what it is, a lot of fun!
 
If you’re doing rifle-length gas 20”, then the port will be between what a .260 Rem and .308 is.

I’ve seen .094” ports on 20” .308 barrels from Krieger.

Some shops have used .086” ports on .260 Remington (less bore volume, slower powders, higher port pressure).

There isn’t an established standard for either, but a few shops who know what they are doing have done the legwork years ago on different chamberings in the large frame guns. Accuracy Systems out of Colorado has done a lot of 7mm-08s.

It will also depend on what projectile weights you plan to shoot. I think 7mm-08 is a good idea if you can find ammo for it. Earlier during the first months of the panic, you would still see 7mm-08 on the shelf but .308 gone, so there’s one reason. Prices will average higher since there is no Mil-Surp or steel case like with .308 Win.

Most factory 7mm-08 is in the lighter 120-150gr projectile weight range, not the heavier 162-175gr bullets I would be interested in.

You can use an A5 or ArmaLite mid-length RET with a heavier AR-15 length carbine buffer in the 4.5oz region or more with a longer spring if you want a telescoping stock. You can also use a standard AR-15 carbine RET with the tiny .308 carbine buffer and .308 carbine spring.

If you use a rifle-length RET, use a DPMS or ArmaLite length rifle buffer (slightly shorter than an AR-15 rifle buffer) with 7.62 NATO spring. They have heavier spring weights for the large frame guns.

If you want it done right the first time, I would first call GA Precision or Accuracy Systems.

GAP will do you a GAP-10 G2 in 7mm-08 with a Bartlein barrel and it will run, as well as shoot bug holes.

7mm-08 feeds perfectly from existing AR-10/SR-25 mags.
 
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OP: What are you looking to do with this rifle?

If you want it to be lightweight, consider the 2A Armament Xanthos receiver set and a light contour pipe for a nice hunter.

iu


If you want more of a target gun, consider the LaRue Ultimate Upper Large Frame set.

iu
 
I'm in the process of building a 7mm-08 AR right now. I really like the round with the 162 gn ELD Hornady bullets. I've got a 20" BHW and a 16" Wilson Combat barrel. Not sure which one I'm going to build first.