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Discussion Starter · #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!
 

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Get the gas system and locking ring parts from Bushmaster then find a carbine length gas system blackout barrel (Wilson Combat, Rainier Arms, etc.) and hope Marvin of Nefarious Arms can put them together into a working caliber conversion.
 

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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.
 

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The reason you do not see many for sale is because they are all custom-made. Most of the people who have them made plan on keeping them a while because of the cost of the conversion and time it takes for parts to be delivered, and work to be done.
 

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Discussion Starter · #5 ·
The reason you do not see many for sale is because they are all custom-made. Most of the people who have them made plan on keeping them a while because of the cost of the conversion and time it takes for parts to be delivered, and work to be done.
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.
 

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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.
 

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Discussion Starter · #7 · (Edited)
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.
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.


 

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Um, what? That picture has the charging handle pulled back. Have you tried it with it forward? Still may work, but you said as we can see, and I see that picture showing us that it clears the receiver, not charging handle assembly.
 

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Discussion Starter · #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.
 

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Discussion Starter · #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?

 

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I think you might be missing something. 300blk needs to use a pistol length gas system on a short barrel, really it should with all barrels. This means the gas block will sit right under the charging handle assembly. You can see this type of setup in a couple threads, but I'll post one picture of the modified parts here.

 

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As I mentioned, pistol is the best way. You most likely won't get it running very well with a carbine system with 16", and it probably won't run at all with 14.5" and a carbine system. At least if you want any kind of versatility with ammo.
 

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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.
 

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Discussion Starter · #16 ·
Get the gas system and locking ring parts from Bushmaster then find a carbine length gas system blackout barrel (Wilson Combat, Rainier Arms, etc.) and hope Marvin of Nefarious Arms can put them together into a working caliber conversion.
So this is an AR barrel with locking rings on it instead of the usual barrel nut? Maybe I'll pull the barrel from my 300 blackout pistol upper!
 

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No, it's just an AR barrel. You'll need to get ACR locking ring parts to make it work on an ACR, same as with the barrel from your pistol upper.
 

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Discussion Starter · #19 ·
No, it's just an AR barrel. You'll need to get ACR locking ring parts to make it work on an ACR, same as with the barrel from your pistol upper.
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 ;)
 

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Like others have mentioned you'll need to deal with the gas system. Nobody has announced a complete design as reliability, versatility, and heat management are still being evaluated.
 
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