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Looking for a 300AAC / Blackout barrel

28K views 65 replies 19 participants last post by  kimberkid 
#1 ·
I've seen posts where someone is going to produce barrels in different caliber's but haven't seen any actually for sale ... Of course ultimately I'd like to have the barrel & gas system in one unit ... I suppose that would be a caliber conversion, and they don't seem to exist.

Any advise appreciated!
 
#3 ·
The 300blk conversion isn't that easy of a task to do on the Acr because of the gas system. 300blk generally likes pistol length for best performance and the Acr can't go that short without some minor work.
 
#5 ·
So just call Bushmaster and order everything but the barrel?

Any idea what that runs?

Has anyone looked at modifying an AR barrel in 300 and/or a different piston system like Osprey Defense?
I only ask because I have a Osprey system on the shelf that I was going to put on a gun 10.5" SBR then and after FTF problems I made a call to Osprey Tech Support and their 16" will work for anything down to 11.5" but less that that it experiences the FTF problems that I encountered ... and to their credit I do have one on my 11.5" Colt Commando barrel I run on my M16 and one on my 16" Colt A3 Tactical. They said they were working on a system for barrels from 7" to 11.5 but its still in development.
 
#6 ·
You might be able to modify a new gas system to work with the Acr but does the Acr gas block height match an AR? If not the piston won't line up with the receiver at all. You will also have to tuck everything under the charging handle assembly.
 
#7 · (Edited)
I took the hand-guard off and pulled the barrel ... There's all kind of room up there for the gas piston so all I need is a gas block the correct height with a port the same size as an AR gas tube ... then cut the op-rod to the correct length, I put the Osprey gas piston up there and stuck it in the end of the original gas block and as you can see there is no problem with the charging handle.


 
#9 · (Edited)
duh ... I pulled it back to get the barrel out and didn't release it.

The older I get, the more brain farts I have.

I hate getting old.

I'll do it again tonight.

Actually, as I look at it, I believe the Osprey gas cup and piston will be situated further forward with a gas block that is actually over the port.
In this picture the Osprey gas cup and piston is just sitting in the end of ACR gas block which is quite long I still don't think it will be a problem getting it in there.
 
#10 ·
Here it is with the charge handle forward, I laid the Osprey Defense piston assembly on top in the approximately where it would go with a shorter and custom made gas block. Actually the piston assembly would go back further as I don't have the barrel port and piston port quite lined up.

Back to my original question, are there any barrels out there?

 
#15 ·
You could get it running ok in a couple settings but not all of them running carbine length. I'd recommend pistol length for the best results.

I run my Acr in U mode all the time with 300blk. I love the fact that I don't need to change settings ever when I run suppressed or unsuppressed.
 
#19 ·
I'm kind of putting this on the back burner for now, but I was thinking, if I were to find an AR piston upper in 300BO/AAC/whisper ... Theoretically I could pull the barrel and gas system out, put on locking ring & spacer and as long as it fit under the charge handle ... It should work in my ACR?

To all the members here that have read my posts ... I have a habit of over simplifying things ;)
 
#21 ·
Stop. No you cannot find a drop in barrel. You need to do more research before asking the same question over and over. We've answered you. It's really hard and expensive to do this. If you're not prepared to spend over a grand doing this, and it may not even work, then I advise you buy an AR in blackout.
 
#22 ·
This issue has me interested. Once I get some free time, I'm gonna look into it more. I've been wondering for a while on how to implement a FAL style gas block into a 300 BLK AR. I don't see why the same couldn't be adapted for a 300 ACR barrel. With a fully adjustable block, one could run a carbine or even mid gas system and get decent performance. For those who haven't seen one, FAL's use a multiposition gas block. Each postion, (usually 8-12 settings, depending on model variations) opens up the gas bleed off a little more or little less depending on setting. Making a gas block of this style would not be overly difficult. I certainly don't have the means to mass produce them, but I could prototype one or 2. Would just be a fair amount of machine time. I don't own an Fal anymore so I would need to look at a gas block to see if one could simply be modified to fit the ACR. The tricky part would be to find the starting gas port to work the system with. I know many like the pistol gas system on 300 AR's because you can run anything without changing any gas settings. But as far as I see it, a 10 position system would allow one to really tune the rifle to whatever loads they really like to use.

I think this is a workable idea. Like I said, my time right now won't allow me to investigate this further, will be months before I could. Winter usually slows down for me. If anyone else wants to steal my idea and run with it, go ahead. Be glad to partner our brains and see what kinda damage we could do.
 
#25 · (Edited)
The FAL knob would have a hard time clearing the ACR charging handle for a pistol length gas system and be concealed by the upper receiver in a pistol or carbine length gas system.

With either system a "set it and forget it" seems to be the end result. You just have to hope that the setting works across a wide range of ammo and scenarios. The ACR S/U settings could give you two separate ranges, but this is all coming from a guy who hasn't tinkered with it so take it with a garbage can of salt.
 
#26 ·
There's no way you'll get the ACR to run with a 10.5 inch barrel in 300blk with a carbine system. It might, might run supers with a can, but the problem is more complicated than you might be thinking. It has to do with dwell time. A two position, adjustable block that can be accessed with a 300blk round, through the handguard, would help it run all four ways as long as it's at the pistol length. It was pretty reliable with everything I tried except subs with no can. And I left it on U.

I think that's the best way to go, but the problem is getting it milled. But we know it's possible and honestly it holds up to a lot of heat for how much metal was missing.

Leaving it on U and having it run subs with a can is the best way to do it in my opinion. I would still choose an AR for 300blk, just because of how complicated it is with the ACR. But it did shoot really well.
 
#28 ·
This is what I was thinking as well. I had no expectation that a 10.5 300 would work with a carbine length system. I am well familiar with the issues involved with dwell time. I think my idea with a 14-16 inch system would work pretty well with a carbine length system. The idea was to avoid the chopping and hacking inside the acr itself. (Instead I'd be chopping and hacking on the barrel) Both methods are a fair amount of machine work. But I think an adjustable gas carbine system with a 14-16" barrel would leave one with the true quick change ability of the original Masada concept.
 
#32 ·
Even with 16" barrels it runs better with a pistol length gas system. And trust me, it needs a pistol length system in anything less than 16" and especially for the ACR. 16" blackout guns are long and heavy. The only reason I have a 16" blackout is for those times when I don't have time to do a form 20 and need to go out of state. Also, mine has a pistol length gas system.
 
#33 ·
Anybody remember the barrel someone built with an offset low profile gas block in the pistol position that fed the stock gas block with a gas tube? That seemed like a great way to solve the interference with charging handle tray and get higher cycle pressure. I wonder how well that barrel ran if it ever was completed. Weight wouldn't be optimal, that's the downside.
 
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