The long range AR-15 project

yorke-1

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The goal was to put together a 1000+ yard AR-15. The 264 LBC/Grendel was the obvious first choice but it comes up a little short on performance. I have a 19" CZ 527 in 264 LBC and it's a great caliber but it just has a hard time making it to 1000 yards. I wanted a bullet with a BC of at least .500 moving no slower than 2600 fps and the Grendel just isn't going to do that.

About this time my "adviser" in all things AR-15 (we call him Gunsmith-X because he wants to stay anonymous) hit me up to design a wildcat that would beat the Grendel by at least 150fps from a 20" barrel. Being more familiar with BR rifles than ARs my first thought was the 6mm Dasher. I was told that there are .473 bolt faces floating around for the AR-15 but that they weren't strong enough to run full BR pressures. That's when I stumbled onto the AR Performance 800 series bolts and extensions. It's the bolt on the right.


AR Performance doesn't sell the bolt or matching extension separately, but he happened to have a 20" 6.5 BRX barrel with the matching bolt and extension in stock. I grabbed it as quick as I could get my wallet out! From there it took a few months of stalling and putting off the project before it finally got done. I picked up a billet lower and a side charge upper then sent those plus my barrel off to Gunsmith-X to assemble the whole thing. My only real request was that it be built with a focus on precision, nothing but top quality parts. Since it's going to spend the vast majority of it's time shot off of a bench, the A2 stock made sense. I'm pretty pleased with what I got back!






Load development so far is pretty promising. Forming brass is a simple matter of taking Lapua 6mm BR cases, necking them up to 7mm then sizing them in a 7mm bushing die with a .284" bushing until the action will close on a case. I formed brass with a load of 31gr of Varget and a 123 A-max. Brass comes out 95% formed. I initially wanted to get this rifle up and running for a cow elk hunt scheduled for the last weekend of January. My initial loads were with the 130gr Accubond and IMR 8208 powder. I started at 30gr and worked up to 33.5 before I ran out of Accubonds and time last weekend. My final velocity from the 20" barrel was 2640 fps and this was far from a max charge. I couldn't get my hands on any more accubonds by this weekend so I tried the 130 gr Berger VLDs (not the new hybrids). This time I worked up to 35.5gr of IMR 8208. The results are pretty promising! I only ran 2 rounds at the max charge just trying to save time and because I was too lazy to size a few more pieces of brass.


I'm pretty pleased with the results! 2780 fps from a 20" barreled AR-15 with no pressure signs. The 2 shots that I fired at the top charge are well inside .5" at the 120 yards I was shooting. I won't have time to get the gun running for the elk hunt, but I should be able to get it dialed in after 2 more trips out. From there I'm heading straight to 1000 yards to test it. It should stay supersonic to at least 1200 yards where I shoot. The goal is to be able to hold all the shots on my 10" gong at 1000 yards. We'll see how this works out!

Andrew
 
Do you have a link to those bolts? I have a few wildcats I've designed, but haven't been able to justify building because I didn't know anybody made any .473" bolts for the AR.
 
Do you have a link to those bolts? I have a few wildcats I've designed, but haven't been able to justify building because I didn't know anybody made any .473" bolts for the AR.

This is where I got the barrel and bolt combo from. He doesn't list either the BRX barrels or the bolts anymore.
High performance 5.56, 6.8spc barrels under $200, bolts and muzzle devices

very interesting

keep posting with your load development

these guys seem do be doing it successfully

http://bulletin.accurateshooter.com...br-and-brx-uppers-for-ar-high-power-shooters/

truth is though I am pushing the 105 bergers 2800 to 2900 out of my 6mm AR turbo 40 improved

easily 6br velocities

I checked out the link. $1390 for just the upper! I built my whole gun for about $1200! It looks like they're using a modified upper and BCG to fit their bolt. The ARP bolt and extension work on standard AR receivers and BCGs. I'm just running 6.8 SPC mags and I haven't had any feeding problems yet in the 50 rounds I've fired so far. I wish that the ARP bolts and extensions were available to buy!
 
This is where I got the barrel and bolt combo from. He doesn't list either the BRX barrels or the bolts anymore.
High performance 5.56, 6.8spc barrels under $200, bolts and muzzle devices



I checked out the link. $1390 for just the upper! I built my whole gun for about $1200! It looks like they're using a modified upper and BCG to fit their bolt. The ARP bolt and extension work on standard AR receivers and BCGs. I'm just running 6.8 SPC mags and I haven't had any feeding problems yet in the 50 rounds I've fired so far. I wish that the ARP bolts and extensions were available to buy!

Well I love building these AR's. I have built up several that I thought were pretty accurate. My test is to take 5 five shot groups and see what the real average is. A challenge for rifle and shooter. Anyone can get lucky and shoot one exceptional group.

thought about it for a year before I purchased the 6mm AR turbo 40. Yes he is proud of them. By the time you buy the upper and dies and brass it is a substantial investment.

That said Robert Whitley knows his stuff. I spent 2 weekends working on load development. First one was really fireforming brass. Tried a couple of bullets at a range of powder charges and found this. 5 shots at 100 yrds and it is extremely repeatable.
 

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Great looking rifle! I was wondering if you could tell me what muzzle brake you are running on it? Thank you!

It's a Seekins ATC muzzle brake. It's working great so far. I hope to get out again next week to do some more testing.
 
I've had a chance to shoot it a bit more, but not as much as I'd like. I've settled on a load that throws the 130gr Berger AR Hybrid at 2715fps. I'm hoping to get out next weekend to test it at 1100 yards.
 
Any updates? I'm still wanting to get one of those bolts...

Do you have to use a special barrel extension for that design of the bolt, or does it lockup fine with a standard mil-spec M4 barrel extension?
 
Any updates? I'm still wanting to get one of those bolts...

Do you have to use a special barrel extension for that design of the bolt, or does it lockup fine with a standard mil-spec M4 barrel extension?

I still haven't really had time to shoot this. I finished up a couple other projects and this one just keeps getting bumped further down the list. Given the choice between shooting the 338/408 CT improved or the AR, the 338 wins every time!

This does use a special bolt/extension that AR Performance used to make. From the looks of it they're no longer available from them though. I heard rumors (I can't seem to verify them though) that there is a bit of a legal battle over the design of the custom bolts and extensions and that's why they're not available right now. Having said that, the 7mm Valkyrie uses a bolt that looks pretty much identical to the ARP bolt and 7 Valkyrie barrel packages do seem to be available right now.
 
Do you have a link to those bolts? I have a few wildcats I've designed, but haven't been able to justify building because I didn't know anybody made any .473" bolts for the AR.

Maximum Firearms is making a .473 bolt and barrel extension, that should be good for a project like this. They are 30 RAR bolts that are only turned to .473 rather than .492, so they have extra strength.

Contact | Maxim Firearms
 
458socom bolts are .473 bolt face that are used in AR15's. Are br cartridges more that 65k on pressure, I don't believe so. Why the statement on can't handle the pressure? Sounds like a selling point! The firing pin is more of an issue that the bolt itself. I know you want too believe your gunsmith, but you might want to question that person some more. Not disrespecting.
 
458socom bolts are .473 bolt face that are used in AR15's. Are br cartridges more that 65k on pressure, I don't believe so. Why the statement on can't handle the pressure? Sounds like a selling point! The firing pin is more of an issue that the bolt itself. I know you want too believe your gunsmith, but you might want to question that person some more. Not disrespecting.
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.
 

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