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Building a 300 Blackout Pistol for Home Defense

Arguments, back-and-forth forum posts, and general opinions aside, the 300 Blackout pistol truly is a great home defense weapon, for a few reasons: It’s shorter than a rifle or shotgun. It packs more punch than most handguns. It’s more stable than most handguns. It can host optics, unlike most handguns. It’s more accurate and stable than most handguns. It’s not unwieldy like a rifle or shotgun. It holds more rounds than a shotgun or handgun. It can shoot JHP or home-defense-by-purpose rounds, designed to provide maximum trauma and lethality without over-penetration.

Yes, the 300 Blackout pistol is a good home defense gun. That’s not why we’re here. We’re here to tell you how to build one that does all of that good stuff above, while avoiding all that bad stuff you might deal with in a rifle or shotgun.

Short, Heavy Barrel, Fast Twist Rate

We’re not going for distance here. Compactness and maneuverability will be major benefits in a quick and dirty defense situation. After all, imagine trying to clear a corner or navigate your hallways in the dark, stressed and frightened, with a 26” or longer weapon sporting a long barrel. No good.

For your home-defense 300 Blackout pistol, that means sticking with a 7.5” heavy barrel, the shortest possible barrel that’s considered stable and accurate. Go with something shorter, and you might deal with simply unacceptable accuracy and instability, even at close range. Any longer barrel won’t be necessary and you’ll just be adding dead weight.

Pistol-Length Gas System

We almost don’t need to clarify this, but we will: Go with a pistol-length gas system. You’ll be working with subsonic loads so you avoid over-penetration, and these under-powdered loads produce much less exhaust gas than supersonic loads. That means more opportunity for your weapon to fail to cycle. A pistol gas system accommodates specifically for this drawback, ensuring your pistol runs reliably. You don’t have to suffer a failure to feed or failure to eject when it’s life or death.

Free-Float, Heavy Handguard

This might seem counter-intuitive, but with a compact AR pistol that fires .30-caliber rounds, you’ll want some heft to your gun. Added weight means added stability, less felt recoil, and less barrel rise – this is why we specifically said you should invest in a heavy barrel, too. Why? You’ll be able to control your weapon better, make follow-up shots quicker, and you’ll be able to stay on target more easily. When you’re under duress, every little advantage counts.

We recommend sticking with a free-float Picatinny rail. Picatinny rails aren’t as lightweight, sexy, or modular as M-Lok or Keymod handguards, but they’re rock solid and they provide a few more accessory mounting opportunities thanks to the rail slots’ close proximity. It’s a guarantee that every AR accessory will be more compatible with Picatinny, too, and generally, Picatinny rails are the most secure compared to M-Lok and Keymod. Remember, every little benefit counts.

Pistol Stabilizing Brace

If you thought shouldering a pistol brace was illegal, think again: As we’ve talked about in other topics, the ATF recently clarified their position on the shouldering of AR pistol braces. It’s perfectly legal, they say, as long as you don’t modify it once you install it. That means leaving the strap on, not changing out bolts, and not trying to secure “make it better” in any way.

Using a pistol brace will inarguably provide more recoil management and a better chance at getting shots on target when seconds count. It’ll also help you maneuver more quickly, anchoring your AR pistol to your body so you can move as one unit with your weapon at the high-ready. We also strongly recommend investing in some sort of Foregrip – the Magpul Angled Foregrip works best for AR pistols because it allows you to push against your pistol’s recoil.

Cartridge of Choice

Obviously, avoid using supersonic, 125-grain 300 BLK loads for home defense. These rounds move as fast as your average .223 or 5.56, and they manage to do so carrying twice the grain count. In short, you’ll be sending missiles through your walls, floors and ceilings. Don’t do it.

Stick with subsonic, heavy loads that have expansion tips. Lehigh Defense makes some effective 194-grain subsonic loads that are made for home defense. The same goes for Alexander Arms’ 180-grainers and 205-grain JHP Silverbacks from Gorilla Ammunition.

In Summary

To summarize, building a good home defense 300 Blackout pistol means building a compact, heavy gun that can be stabilized against your body. It also means sticking with subsonic loads that feature expansion tips for maximum trauma and minimal chance of over-penetration.

DISCLAIMER: If you are new to the world of DIY gun building, you likely have a lot of questions and rightfully so. It’s an area that has a lot of questions that, without the correct answers, could have some serious implications. At 300-blackoutupper, we are by no means providing this content on our website to serve as legal advice or legal counsel. We encourage each and every builder to perform their own research around their respective State laws as well as educating themselves on the Federal laws. When performing your own research, please be sure that you are getting your information from a reliable source.


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