Bolt action 300 Blackout AR upper?

[Radny97]

I’ve just built and am working on suppressing an AR-15 pistol in 300 blackout. Fun project. In any case, using sub-sonics the action cycling the AR is the loudest part and I’d like to see if i can get it even quieter. I’ve seen some bolt action suppressed guns shooting subsonic ammo and the quietness is truly impressive.
So . . . here’s my question. I’m thinking of purchasing or building an AR upper in 300 blackout that is not gas operated. Thinking of a bolt action or maybe a side charging action without a gas hole in the barrel. There are several different options. Doing some searches, some people had trouble with the cases sticking in the chamber and not being easy to cycle manually.
Has anyone done this and can tell me your experience? Also, not interested in dropping a fortune on this. Trying to stay under $500. Thanks in advance.


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[MagnumWill]

A friend and I have been exploring this too, after mixing Trail Boss and 150gr bullets that are insanely quiet but don't cycle the action.

Check out the KALI-KEY. It's a charging handle that is mounted on a gas key with no flow-through.

Instead of retrofitting it onto your BCG, go buy a bolt carrier from PSA for $50 and install the gas key. That should effectively turn your current upper into a bolt action, then just switching out the BCG's you're back in business with a semi auto. As much as I love new uppers, having SPECIFICALLY for this would seem a little cumbersome. A lot easier to toss a BCG in your bag or pack with you instead.

https://www.guns.com/news/2019/02/05...t-action-rifle

It's intended to help CA residents stay compliant, then people realized one of its alternate uses is keeping a semi auto action from moving when you don't want it to

[Bartholomew Roberts]

You could also use an adjustable gas block/adjustable gas carrier and just turn the gas off when you want a straight pull bolt action.

[bull bob]

I have been playing with a similar project, a straight pull using a side charging upper in 6.5 Grendel. Problem I kept having was the cases sticking in the chamber after firing. I started with the gas port totally blocked off.

I think I have solved my problem by opening up the gas port and using an adjustable gas block to put some gas back against the bolt. This seems to loosen things up enough to function with just a simple pull of the handle.

Good luck.

[MagnumWill]

That's why it makes sense to stick with subsonic ammo for something like this. After firing, it hardly resized the brass at all so it's still really easy to extract. Full house loads expanding into the chamber are way harder to get out if you don't have something like the camming action of a bolt action.

[Radny97]

Originally Posted by MagnumWill

A friend and I have been exploring this too, after mixing Trail Boss and 150gr bullets that are insanely quiet but don't cycle the action.



Check out the KALI-KEY. It's a charging handle that is mounted on a gas key with no flow-through.



Instead of retrofitting it onto your BCG, go buy a bolt carrier from PSA for $50 and install the gas key. That should effectively turn your current upper into a bolt action, then just switching out the BCG's you're back in business with a semi auto. As much as I love new uppers, having SPECIFICALLY for this would seem a little cumbersome. A lot easier to toss a BCG in your bag or pack with you instead.



https://www.guns.com/news/2019/02/05...t-action-rifle



It's intended to help CA residents stay compliant, then people realized one of its alternate uses is keeping a semi auto action from moving when you don't want it to

Perfect!


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[Radny97]

Originally Posted by MagnumWill

That's why it makes sense to stick with subsonic ammo for something like this. After firing, it hardly resized the brass at all so it's still really easy to extract. Full house loads expanding into the chamber are way harder to get out if you don't have something like the camming action of a bolt action.

Thank you!


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[MagnumWill]

You bet!

Also, I learned that filling the .300BLK case to the very tip-top with Trail Boss and then loading the 150gr to max length (2.26") still doesn't cycle an action anyway. On to a different powder, if I need semi auto.

[mxsailor803]

I’ve got a couple .300blk in bolt actions and AR’s. If you want to try some thing that is stupid fun, look for 86gr .30Mauser bullets and pack the case full of trailboss. Still won’t cycle a semi auto but it’s crazy accurate from my 700’s inside of 50yds. A buddy of mine and me would set up a paper target that was stapled to a back board and try to see if we could hit the staples lol.

[FizzyP]

Regarding @Bartholomew Roberts's suggestion about an adjustable gas block. I've been eyeballing these SLR 7 adjustable gas blocks. They're designed to be adjusted on the fly. Not the set screw type that are more "get it adjusted and leave it indefinitely". They advertise "off" as a setting. I've written to some other manufacturers of click-adjustable gas blocks. So far they've all said either 1) true off isn't really possible or 2) you can sorta turn it off but it gums up the works eventually.

https://slrrifleworks.com/sentry-7-c...lock-titanium/