DIY: Shortest 300BLK Gas Operated AR15?

by Pete

An innovative shooter/builder has just laid claim to what could be the the shortest 300BLK gas operated AR15 in existance. Measuring at a mere 3.75” inches, the barrel real estate is covered primarily by the gas block with just enough room for a threaded muzzle to attach a suppressor. After watching the below posted videos, the unique setup appears to function reliably with the shooters own reloaded ammunition.

For all those wondering, the builder ended up with a 0.100 gas port size. For comparison, depending on the barrel length and ammo tuning, standard gas port sizes can run from 0.086 inches with eight inch barrels and 0.12 inches for 16” barrels. On the other hand, typical 5.56 gas port sizes range from 0.069 to 0.089.

In the past, has been criticized for pseudo-teenage musings on everything from over accessorizing pistols and rifles to beans/no beans chili debates. Over the years, my experience has been overwhelmingly positive, with the different forums for platforms, manufacturers and components. I owe much of my knowledge on silencers and ARs to and it projects like the one shown here that sparked my own curiosity to build unique projects.

To answer the question that many are asking: why build the worlds shortest gas operated 300BLK AR? Because he can.

Check out the videos and other details below.

Shortest 300BLK Gas Operated AR15?

Second Test Fire:

No Suppressor Attached:

It is a one in 10 twist, so I am currently limiting to around 200gr bullets or lighter. At this point I have not shot it for groups yet. However I have fired several rounds at a large piece of cardboard and 155gr cast, 140gr tracers and 200gr cast have all left mostly circle holes. There have been a few that were slightly out of round but not enough to where I, at this point am overly concerned.

This was not built for any real purpose other than I wanted to see if it could be done. Not really practical. I guess in theory it could make a cool PDW, but not a first choice for that.

I have a few subsonic loads that I like for reliability, but as I said still got to get them on paper. I have managed to push a super load to 1300fps using the 140gr tracer. But I think I can get it faster than that. I am hoping close to 1500fps. But only testing will tell. Garyd – member –


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2 of 64 comments
  • Brah Brah on May 25, 2018

    Maybe Sir could add one of those little fatty Brevis suppressors for ultra smallness

  • Spike1984 Spike1984 on Jun 07, 2018

    The AAC Honey Badger's straight-edged 300 Blackout magazine is based on the legacy AR-10 rifle but it can also use the curved 5.56 AR-15 magazines.