ACR Forum banner

6.5/.264 acr

55K views 90 replies 35 participants last post by  bigdog2003_99 
#1 ·
The following is most of the information for my conversion of my Bushmaster ACR from .223 Remington to .264 LBC-AR (aka 6.5 Grendel). If you think I left something technical out of this, you are correct and I did so for a reason. I know this rifle is very friendly to users looking to customize without a gunsmith but I think doing this kind of work entails more than a bit of danger if you are just ‘winging it’ without previous training and experience in Firearms Engineering (which I possess, especially with this rifle). I don’t want a job either, Firefighting allows me to do fun side stuff like this so why would I work for someone ever again. Also, I won’t coach anybody through a build like this because of possible liability issues. When I am satisfied that the parts are safe, I do intend to make the components available to everybody that believes in this platform as much as I do. Here are the tech specs:

Machine gun Air gun Trigger Wood Gun barrel


Air gun Machine gun Trigger Gun barrel Gun accessory



Custom made 20” Stainless Heavy-Mid profile Fluted Barrel, .264 LBC-AR chamber
Standard ACR upper and bolt carrier group
Custom made ACR bolt for the .264 caliber (this would also fire a 7.62x39 round if the barrel was chambered for it)
Standard lower
Rock River Arms National Match Trigger group
Prototype ACR to PRS2 adapter
Magpul PRS2
C products 6.5 magazines(blue follower)
Hornady 6.5 Grendel 123 gr Amax Ammunition
Burris Optics Black Diamond 8-32x50mm Scope and Burris 30mm Signature Zee Rings
Mako Group Grip pod Bipod/Vertical Foregrip

This build has taken me about a year to assemble all the pieces with my finances the way they are and two kids(three if you count the wife). Some of the parts are irreplaceable right now so I won’t be thinking of selling any of them until I do a commercial sized run of parts. If I had to guess at the final price tag with all the engineering work, parts, and testing I would figure that I have easily quadrupled the msrp of this rifle. That’s pretty typical for this kind of work though.
I should also note that I have had advanced military training so I shoot well but I think this rifle could shoot even better in the hands of a shooter that is trained and experienced in the art of long range shooting. I can read trace, mirage and wind but I don’t make my living at it.
I have omitted the name of the barrel manufacturer because I would not recommend them to anyone(maybe someone I don’t like) and I won’t use that manufacturer for any build in the future. If you figure out who did the barrel and want to use them, good luck and you will be using a couple of calendars to measure how long it’s going to take to get a barrel out of them. I got ‘hooked up’ because I was ‘in the industry’ and it took 8 months and they doubled the quoted price at the end. The bolt was fabricated by a local machinist that is very talented and he will be the one making future bolts for me. Also, thank you to Keith at Rocky Mountain Shooters for getting some clean up gunsmithing done for me very quickly at a great price. If you are in the area I recommend him. I had no problems with the C Products magazines but they aren’t in business any longer so I consider them good enough for this build. I don’t know that I would trust my life to them yet. The only malfunctions I had with this gun were when I was working with the gas system to get the rifle gas port tuned to the action. I attribute those malfunctions to a non-tuned gas system rather than the rifle or the magazine. The grip pod was fun and may have some applicability to this platform. I wish it was a bit smaller and lighter because it is pretty huge in real life. The trigger group from RRA is good enough for me. I noticed the difference switching from the OEM trigger but I don’t think I would be good enough to tell the difference in the Geissele trigger compared to the RRA, although I would love to try it out if I had the cash for curiosity. The RRA trigger is the value buy for me on this build. Thanks to Hornady, if it wasn’t for them I would be buying Wolf. The rounds have been great every time out of the pipe. Thanks to the Burris Guys for the hookup on the Black Diamond and rings. I used to work there and I know how good that scope is from an engineering standpoint. It held up its end on this build and was more than cost effective considering the shooter. Finally a big thanks to Magpul for letting me work on the Masada in the prototype phases which gave me intimate knowledge of this platform and a solid knowledge base to attempt this endeavor. Even though I don’t work there anymore I still consider the guys and gals over there to be good friends and more than helpful when I needed some help.
I figure the rifle shoots just under 1 MOA or better which is ok for a precision gas gun and a moderately skilled precision shooter. The weight comes in at 12.4 lbs with an empty magazine according to the bathroom scale. The recoil is very comfortable and the bang is quiet enough that some people/cows over the next rise didn’t even know I was shooting until they came over. I did not notice any change in POI shift by removing the barrel and replacing it but I don’t plan to do that very often for this prototype setup because it may turn up in the longer range shots. The barrel tip is threaded because I would like to fabricate my own suppressor for this system in the future (BATF, don’t worry I know the rules for that sort of thing). In the pics to follow, all the distances are in yards even though a couple of the targets have meter designations (old habit). This rifle will shoot all day long at 600. Especially since I can turn up the magnification to 32x and the groups go to very good (I used a controversial target so I am not positing that it). The other ranges require the scope to be at 14x for the reticle to match the ballistics calculator I was using. Counting all the rounds I used for tuning the gas system, sight in, and then range days, I have about 150 rounds down the pipe. I haven’t seen any major signs of wear and tear or damage but I plan to inspect the bolt with some industry standard inspection practices to make sure there is nothing I am missing on this one.
All in all I am very happy with this build and I am also happy that I can put it down just in time for archery season. Maybe after I fill the freezer with elk and I get the 6.5 bolts done I will work on a 7.62x39 setup(I might use Wolf ammo then) and then who knows what I will add to this platform. I will post again about this stuff when I have the company formed and am ready to take preorders for the first run of bolts. Thanks for taking the time to read this.

Mike
 
See less See more
2
#61 ·
Chiburi,
I have proved at the start of this thread that the 6.5 works in the ACR. I have, as far as I know, the only functioning 6.5 ACR. I am only selling the bolt because the rest can be procured through other vendors and that leaves me open to pursue the next project with my company instead of trying to pull together all those parts and sell packages. When I did the proto 6.5, the bolt was the only thing I had to fabricate from scratch. I am still dialing in the gas port size but mine runs consistently with with a fairly common gas port size. The 6.5 bolt can also be used for a 7.62x39 chambering so it made sense from a startup perspective to do this bolt first. I understand your caution in buying something that will require procurement of several other parts and all I can say is please be patient. I understand the difficulties with making the Adaptive Combat Rifle actually live up to it's name but I fully intend to do this as a start up company if huge companys like Remington and Bushmaster won't.

CJ and Tack thanks for covering for me while I was at work yesterday. Probies don't get a lot of free time at the station. Ducky quit posting dumb stuff, I expect better from you given your background.

Mike
 
#63 ·
Ok fellas,

Updates
1. quotes are almost finished coming in, again. I had to have them redone. I have learned quite a bit about such a 'simple' part. I wanted it to be right so it took a long time to finish this project. If the first project is not right why would you consider buying anything else I try to sell. And I have a list of projects I want to do for this rifle (2 more modeled and waiting for me to do the drawings).

2. fired a 7.62x39 round three times with the 6.5 bolt just to prove that it works. Barrel was an off-the-shelf barrel from Yankee Hill. I didn't bother hooking up the gas system because this was just a proof of concept. Picture below.


Machine gun Air gun Trigger Gun barrel Gun accessory


Hang in there. We are almost at the beginning of the key component for the 6.5 Grendel/7.62x39 caliber conversion being available.

Mike
 
#66 ·
I hope this does not constitute hijacking , but rather a contribution made to further everyones enthusiasm for the bolts www.ar15performance.com has 16 inch melonited barrels in 7.62x39 with midlength gas and custom gas port diameter for $165.00! I love mine !!
 
#67 ·
Order up!

Thank you all for waiting patiently for this caliber conversion. I have cut the purchase order for the first lot of ACR 6.5 Grendel / 7.62x39 bolts. They should be shipping in the third or fourth week of January 2012.

The bolt will be as close to industry specifications but they are my best reverse engineered guess. The bolts will be made from the correct material for this caliber, hardened, shot-peened, and electroless nickel plated (so you can easily tell it from your 5.56 bolt). I have tested this bolt with my 6.5/.264 LBC AR barrel (barrel head-spaced to the prototype bolt) and with a 7.62x39 barrel (off the shelf and checked for headspacing). It worked with both of them. I don't have the gas port sizes for either caliber other than the current gas port setup I have for the 20" 6.5 Grendel. The bolts will come stripped so they will require an extractor claw,pin, and spring as well as an ejector pin, retaining pin, and spring. I will include a data sheet and useful information with every bolt I sell.

The price will be $115+shipping per bolt. You will probably save on the shipping cost on the second bolt if you buy two. Maximum of two per person for the first few production runs. I will not ship out of the country or any where these parts would somehow be illegal. If you want to guarantee you get one or two bolts from the first batch send me a check or money order with half the cost of the bolt(s). The company name is Argonauts ReIncorporated Ltd., address is: 933 Nantucket Street Windsor, CO 80550. The rest of the bolts will be available on a first come first served basis and availability will be noted on the website(www.argonautsreinc.com) when I have that functioning. If you do send me a preorder and have an account on this site, or an email address, let me know so I can confirm that I have your preorder. Please feel free to mention this to anyone you might know that would want one. After I get the first batch of bolts through I plan to contribute as a sponsor to this site. Thanks


Mike Morgan (artist formerly known as Nagrom3)
Argonauts ReInc.
www.argonautsreinc.com
 
#68 ·
Update 35.
I approved the final cuts on the bolts today. They are behind schedule but not by a lot. The short story is that the company I was working with got bought out and it set us back 2 weeks. I have checks from multiple people and they will be getting their bolts in the order the checks came in. BFelt and Sam are on this site so this is their notice that I have their bolt reserved. Thanks to all the people jumping in on faith, it has helped me get started and I will not let you guys down. That said, the next project is going to be much simpler. I will let it slip when I have this project wrapped up and running smoothly but I am working on it in the background already(it's modeled and I have requests for quotes out already).

Mike
 
#70 ·
Mike, Thanks for keeping all of us constantly updated looks like everything is coming together nicely. I like lots of others are keeping track of your progress and as you know are extremely interested. I'm still holding out hope that you will be offering these conversions as complete drop in (plug & play) kit. As you know getting the extra parts to complete a spare barrel from Bushmaster / Remington is spotty at best and some of them are impossible to get right now. I'm guessing this is due to the fact they are holding them back for there own barrel kits. Keep up the good work.
 
#80 ·
A ton of performance would be lost for a 6.5G built on a 10.5". A 16" barrel is going to loose about 200 fps off the muzzle velocity which will affect downrange accuracy. I know of one person that has a 16" 6.5G ACR and he is happy with the accuracy.

As a bit of info on this cartridge, it is built for accuracy and slow fire. A 10.5" barrel is built for maneuverability, short distance shooting and quick fire. You might want to stick with the 7.62x39 if you want a shorter barrel on the ACR.
 
#83 ·
Bit of a thread revival, I have a shilen 6.5 barreled ar I'm going to send to Marvin for conversion. I know it shoots in the AR so I'll be interested to see what happens in the ACR. Now all I need is the bolt and bushmaster to ship the guide block and lock ring handle. I've had this in mind since the Masada days so hopefully this will be as great as I think it will be.
 
#84 ·
anyone know where I can get a BBL from?
 
#86 ·
Depends on what you want. Black Hole Weaponry sells good barrels but it's a 264-LBC chamber, not a true Grendel. Not that you could tell the difference out of an ACR. I got my barrel from Alexander Arms and would not suggest that route. It was probably a fluke, but my chamber was way out of spec, I had to have it throated by my smith. JP sells Grendel barrels, as do Saturn and Lilja. Any of those is likely to be excellent quality. On the cheaper end, Midway occasionally sells barrels under the Stoner name. I think ER Shaw may manufacture those, but don't take my word for it. Model 1 may sell some cheaper stuff as well.

All told, if I was to do it again, I'd go BHW.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top