Projects Can Get Weird…
I’m definitely not a stranger to putting together some pretty awesome AR-15 based firearm builds. I’ve built shorties, long boys and every thing in between. Retro and modern as well as a mixture of both. Probably a year ago I started to think about some of my “needs” for a future build and what I’m missing in my firearm collection. One of those is a short .300 Blackout bolt action rifle. Now I could easily purchase a barreled Howa mini action from Brownells and get the barrel chopped down and threaded for a can. My main reason for wanting a .300 Blackout is because I’m getting more and more into suppressor testing and it would be nice to have something that won’t exhibit port pop like a gas gun like an AR-15 will. The thing is… I love the AR-15 platform! So what options do I have for a bolt action that’s essentially an AR-15 rifle? I already had an ambitious BRN-180 lower receiver from Brownells sitting there… what to do?
With some simple searching I was pretty sure I found my option. BCA makes a bolt action upper receiver that will fit on any AR-15 lower, no problem. Well there’s kind of a problem. The bolt is long and requires a buffer tube. But I want a folder. After some additional digging, it would appear that people cut down the carrier so that it’s shorter so that you can run a side folding stock assembly. This is it! It’ll be a weird combination of upper and lower receiver not to mention the butchered bolt carrier, but this should work very very well. Since I’m a HUGE fan of Geissele stuff, I went over to Brownells and placed an order for their MK4 hand guard in DDC. My plan was to do the build in black but with tan.brown accented parts. Other Geissele parts included their lower parts kit and G2S trigger assembly which I’ve used in the past. In terms of Geissele triggers, the G2S is one of the cheapest Geissele triggers but feels similar to the SSA trigger. Other parts included a Samson MFG side folding skeletonized mechanism, an SB Tactical SBA3 brace and the Die Free Co Kung Fu grip. The barrel is a Faxon premium gunner profile 10.5” .300 Blackout barrel.
So here we have a plethora of cheap parts revolving around a super duper budget bolt action upper receiver and bolt assembly. In order for the Mk4 hand guard to fit I had to cut the anti rotation tabs off of the rear portion of the hand guard. For the lower receiver to work, I needed to cut down the bolt carrier assembly. Needless to say, the bolt action portion is pretty rough to manipulate, but hopefully I’ll find some places I can polish to smooth it up. One other thing I needed for this to work is a way to block the gas port on the barrel. I didn’t have a .625 gas block on hand so off to order one from Brownells and it should be here within the next couple of days.
So this build got weird really, really fast! Never in my dreams did I think I’d buy a cheap receiver like this and surround it with such top tier parts. Cutting the bolt carrier wasn’t a huge deal since those parts were cheap, but cutting those anti rotation tabs off the Geissele MK4 hand guard, well I’ll be having nightmares about that for years to come. Hopefully everything works well once I’m finished otherwise I’ve had spent a ton of time and money on a weird project that will remain a project.
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