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Gentlemen, Any thoughts on the 300 AAC Blackout in a HK or Vector platform? This caliber seems to be catching on in the AR world and would like to know if it is adaptable to an HK system. Any information would be helpful. Thanks.
Eagle45
 

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I have been discussing with my gunsmith who has built many HKs doing an integrally suppressed HK(like the MP5SD) in .300 blackout for a while now and the biggest hurdles I have discovered all deal with the barrel and action.

You're going to need a 1:8 .308 barrel that is chambered for .300blk, then get it chamber fluted for a .223. The best way I've figured to do this, is unfortunately doing it all yourself. You'd need a 1:8 1.3" OD .308 stainless barrel that you would need to cut to length, turn down for size, chamber, and flute. I saw on here from years ago the guy who fluted barrels using a go-gauge and a tool steel "toothpick" using a CNC machine, either doing that yourself, or finding someone who can flute it for you would be required. You'd also need to calculate the flute length, width, and depth; from my research I think it'll be standard .223 flutes, just slightly shorter.

The second issue I found was that the HK .223 magazines do not like having .300blk in them, so you'd need to build it on an HK53/93 receiver with an AR magwell.

The third issue is rollers, locking pieces, and the bolt retaining arm(someone chime in with the actual name, no idea what it is). You're going to need to test and see which rollers and locking pieces work with the round the best, and if you want to change between shooting supersonic and subsonic, you're going to have to change the locking piece as well. The recoil pressure of the .300blk is very close to that of the .223, but the recoil impulse is different, because it is a much heavier bullet going much slower. The bolt retaining arm might require a reduced spring because of this.

All in all, it is very doable, but it's going to require a lot of R&D on your end to get it functioning correctly.
 

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Gentlemen, Any thoughts on the 300 AAC Blackout in a HK or Vector platform? This caliber seems to be catching on in the AR world and would like to know if it is adaptable to an HK system. Any information would be helpful.
Absolutely adaptable, but a pricey project, as there will be quite a few one-off custom built parts needed, and a VERY limited market to sell those parts to if you ever wanted to recoup some R&D costs.

Couple that with the H&K roller locks are a bit less great for suppression, and a few of the blackouts advantages go away.

Heck if you've got 5-20k you don't know what to do with, go for it!
 
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