I've decided to build an AR15 pistol in .300 AAC (Blackout). Although I own several "sporting rifles" and an SBR (ARs, AKs, MPX), I've never actually built one.

Here's my progression so far, and where I intend to go with this build. I started with a Palmetto State Armory AR15 .300 AAC upper with threaded 8" bbl. that I got from my son. It didn't come with BCG or charging handle, so it now has a Bravo Company bolt carrier group (with Carpenter C158 bolt) and BCM Gunfighter ambi charging handle. The PSA hand guard has been changed to a Tacstar 10" carbon fiber hand guard. I just ordered a PSA complete lower in FDE (Christmas special pricing), which should be here next week. As soon as it arrives, I'll add some FDE Magpul F/R folding iron sights, small M-lok rails, Magpul FDE angled hand stop grip, and a couple of Magpul .300 Blackout magazines. I may add a new Magpul fatter pistol grip, too. My pistol will be kind of a pinto pistol- mixing black with FDE. Right now I'm looking at direct thread mount suppressors, and hope to get either an Otter Creek Polonium 30, Aero Precision Lahar 30/30K, or Dead Air Nomad 30. This is a budget build, so I'm looking at keeping the price of the suppressor reasonable while still being effective. And then there's the ATF stamp fee! All of these entry-level suppressors are currently out of stock so I'll have to wait (my son manages a local gun store so he'll keep checking with his distributors for me). Well, that's about it. I will most likely add a weapon light and sling down the road but that's easy. I like iron sights for close in work, but I also have a couple of Red Dot scopes that can be mounted. I calculate that I'll have a complete and functional .300 AAC pistol with suppressor for under $1300...not too bad. I will post some more pics as the project progresses. Happy New Year!

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I have something like a M-4 carbine, stainless 18" barrel. FDE M-lock fore end. I have an adapter to put an old MAC-10 9mm suppressor on it. It is long with the can on! It is also very quiet!

I have Tan accessories, so I have a wrap of tan tape to designate 300 BO loaded mags from my regular 223. Been looking at night scopes for pigs and coyotes but haven't found a price I want to live with! Currently have a Leupold 4.5-14x40AO scope with folding backup sights. I install a stud for a Harris bipod (about 79 cents) for if I want one. No bells, whistled, or commando gear!

I have about $500 in the gun build 2 years ago. The Suppressor was $400 back in 1983 + $200 stamp + $50 local fee. I make my ammo from trimmed 223 brass.

Ivan

Build my pistol using Sale priced items.
Purchased through various online stores. This build took several months.
The upper was an Anderson slick side” no forward assist” , 10.5” Odin works SS Match grade barrel, adjust gas block, tool craft bcg, and a matching nickel boron T charge handle, YHM hand guard. Muzzle device is Silencerco ASR mount.
The lower is Andro Corp lower, Enhanced trigger from Spikes Tactical, PSA FDE Brace and lower parts kit.
My mags are marked 300 Bo. And they are metal. Vs Magpul.
Shoots good. fun to build it out.
It’s Lego’s for old dudes.
Really like thinking about the time I had building that thing out.
My son watched and assisted when he could. He was probably 10 yrs old.

Papa

Just finished Phase I of my budget .300 AAC pistol build, assembling the upper, lower, rails, sights, magazines, etc. Phase II will be the addition of a suppressor. Unfortunately most of my budget direct thread mount suppressor choices are Out of Stock due to the Holidays so I'll have to wait a while. I may have to invest in a 2"+ long muzzle device in the meantime so that I can take the pistol to the range. Phase III will be weapon light, sling, and perhaps a Red Dot.

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Fun caliber, I like it a lot. Suppressed Supers hit hard and do a number on whatever they hit.
Just in case you don't know... be very careful if you have a 556 too.. lots of rifles have been blown up when a 300 gets mixed in a 556..

__________________
Plastic has no soul

I will confess I shot 223 in my 300bo.
Once.
Now I don’t have them both on the bench st the same time.

No harm done, but the lesson learned.

Papa

I just put together a budget pistol very similar to the OP's 300 blackout. PSA 8 1/2 inch barrel upper, PSA lower with flat dark earth grip and brace, and Holosun 510C circle dot site. Absolutely love the circle dot site like I have on my Sig 365 XL 9mm pistol. I’ve been approved by the ATF and should be getting my YKM Resonator K 30 Silencer soon and bought some Sellier and Bellot 220 grain subsonic and also some high velocity rounds but I imagine I’ll be doing most of my shooting with subsonic. Got some decent X-mas pricing, $299 upper, $159 lower with enhanced trigger, $265 Holosun, $530 YKM suppressor, $305 for tax stamp, trust, and gun shop fees. I do wish I had the brace that's on Hawg Riders gun.

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I have separate metal mags marked 300BLK so there’s no issue about what mags go with which.

__________________
I’m your Boogie Man, uh huh.

Yep, I made the exact choice.
After my error.

Papa

I was warned before even buying a 300.

__________________
I’m your Boogie Man, uh huh.

I actually purchased a couple of Magpul .300 AAC magazines so I won't get them mixed up with 5.56. I've read that although .300 works OK in 5.56 magazines, reliable feeding can sometimes be compromised due to the larger size .300 rounds and how they stack inside the magazines. This may just be scuttlebutt, but for the price of the .300 mags I'm not worried about it.

These are the mags I bought. Clearly marked and metal so as not to be confused.

.300 Blackout Firearm Magazine | D&H Tactical

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I’m your Boogie Man, uh huh.

I really like Tango Down's MK3 magazines, but they only make them in 5.56. I did contact their Customer Service to see if they would consider making some in .300 AAC (Blackout).

That would be an easy fix for the Tango Down magazines.

They sell custom branding irons for Very Little,,

That Tango Down has a perfect area area on the lower portion that could be easily marked.

I guess that could work on any plastic magazine??

I just looked, a custom branding iron is under $23 on Amazon,,



Here is what they will mark,,

Those irons are pretty cool! May have to get one for my grill and smoker!

Tango Down's Customer Service replied to me that there are no immediate plans to make MK3 .300 BO magazines...not enough interest yet because the ammo is more expensive than 5.56 and there is a limited market for the mags.

My .300 BO pistol build is nearly complete. I am getting a Magpul ASAP QD mount for the back of the receiver for a single point sling, and waiting for suppressors to get back in stock.

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it's the opposite that causes the problems...

__________________
Plastic has no soul

Just finished up my "Christmas" build of a AR .300 AAC Blackout pistol. I took off the stock and buffer tube and installed a Magpul ASAP QD single point sling adapter on the receiver. I really struggled getting the castle nut loose because Palmetto State Armory really staked (actually double staked) the original plate to the castle nut. Finally got the castle nut loose and was able to save it and reinstall it with the Magpul ASAP. I did re-stake the nut, following Brownell's YouTube instructions. Then I installed my Silencerco Omega 300 suppressor. It was actually a very fast approval from the ATF...I submitted my Form 4 last Thursday and had my approval on Tuesday (that included a weekend and the MLK Day holiday). Anyway, here is my completed build. I have several red dot scopes if I decide to add one later. Enjoy!

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Always wanted one but never did.
Great truck/HD tool. IMO
Prices are prob best, in a long time and might be 10% less
in 6-12 mo. IDK
Good job guys !!