Troy A4 Other Firearm 9mm Review: Glock-Mag PCC Worth It?

Hey channel fans and family, and welcome to Slav Guns. Want an “other firearm” or an SBR-style setup without a tax stamp, but can’t decide between 5.56 and 9mm? After all, there are Glocks everywhere. In this one I’m looking at the Troy A4 “Other Firearm” in 9mm — a pistol caliber AR built to run on Glock magazines.

Disclosure: The firearm was provided by Tech Ops International for testing and evaluation. Tech Ops International did not see the video prior to publication.

What is an “other firearm”?

For my friends in free America screaming “you can’t put a vertical foregrip on a pistol!” — this isn’t a pistol. An other firearm is designed to be fired with two hands and ships from the factory with a vertical foregrip, so it’s not a pistol. It comes with a brace and not a stock, so it’s not a rifle. And because overall length is over 26 inches, it’s not an AOW either. People confuse AOW and other firearm all the time, but they are two different categories.

That is why these became the hottest sellers in banned states like New Jersey and Connecticut: the state laws were written for handguns and long guns, not other firearms. That’s how you get the adjustable brace, shorter barrel, flash hiders and threaded barrels that you can’t have on a standard AR there. The main thing that still applies is the 10-round magazine limit. (That’s how it stood when I filmed this — always check your current laws.)

Front end: barrel, brake and rail

The 13.5″ barrel has 1:10 rifling and, like other pistol caliber carbines, runs direct blowback. Up front is the Troy Claymore brake. It does help with muzzle flip, but its main job is pushing blast and sound forward, away from you — your range mates will thank you. Personally? Loud brakes save lives.

The brake and barrel are threaded 1/2×36 and the barrel is not pinned, so you can swap the muzzle device — and if you come visit America or move, you can throw a suppressor on. Just remember it’s 1/2×36, not 1/2×28. If your cans are 1/2×28, you’ll want the right adapter.

The rail is the same 10″ Troy SOCC rail as on the 5.56 models: free floated, full-length Picatinny on top for lights, lasers, optics and backup sights, and M-LOK slots in seven positions (five of them practically usable). It’s nicely sized for whatever grip style you like, including C-clamp. The Troy CQB vertical grip has a waterproof compartment for batteries or a spare round or two.

Upper, brace and grip

Something you typically only find on Troy other firearms: real Troy folding battle sights, not polymer — most other firearms come optics-ready with no sights. The upper has a brass deflector, which should help when shooting a short 9mm round in an upper designed for 5.56, plus a standard charging handle.

Out back is the SB Tactical brace on a five-position buffer tube. The Troy Control grip is meaningfully more upright than a standard AR grip, which I like for keeping the gun close and for pulling the trigger more straight back on precision shots. It has a storage compartment too. The trigger is stock mil-spec — nothing to write home about, but not abnormally bad.

The 9mm part: Glock mags

The lower is built around small-frame Glock magazines: standard 17-rounders, compact and subcompact Glock 19 and 26 mags, and 33-round sticks like Amend2. Troy kept the magazine release in the same place as a traditional AR-15, gave it a last-round bolt hold-open (reliable so far), and added a beveled mag well to help reloads. In NJ and CT it shipped with 10-round Glock 26 mags.

On the range

Honestly, it was more fun than I remembered. Even with the flip-up sights the gun is stupid accurate, and it locked back on the last round every time — one of the common PCC pain points. I ran Glock, Magpul and ETS and Amend2 mags, including 33-rounders, and all were reliable. My pick is the Amend2 mags. Compared to a Ruger PC Charger, the Charger is a more compact package, but the Troy has better ergonomics because, well, it’s an AR — perfect as a training tool for a regular AR.

9mm vs 5.56 — which should you buy?

Maybe. It depends on where you live and what you already own. If you’re a first-time gun owner with a Glock, the Troy 9mm gives you magazine and ammo commonality. Over-penetration? 9mm can do that too; it largely depends on your bullets.

Likely contrary to what many of you believe, the 5.56 version actually has less felt recoil. It’s a gas gun, which gives a smoother delayed impulse, while the 9mm is direct blowback. Not a lot more recoil, but noticeable. 9mm is generally cheaper to shoot, which is why many people look at PCC ARs as trainers.

I also have to point out that pistol caliber ARs are typically not as reliable as rifle ARs — feeding and lock-back issues are common because you’re adapting a rifle-length action to a much shorter cartridge. The Troy has been reliable for me, but I don’t expect it to match the 5.56 version, which has given me thousands of trouble-free rounds, including 1,000 rounds in an hour. So my personal preference is the 5.56.

The caveat: many ranges have action pits that don’t allow rifle calibers but do allow pistol calibers — that’s where the Troy 9mm works. For the ultimate PDW in a free state I’d still take a Ruger PC Charger with a suppressor any day of the week and twice on Sunday. But in New Jersey or Connecticut that’s not even close to legal, so the real choice is Troy A4 9mm vs something like a Ruger PC Carbine — and that’s where the Troy and other 9mm ARs are more appealing: better ergonomics, an adjustable brace, and swappable muzzle devices.

Related: Troy A4 AR-15 Other Firearm (5.56) detailed review · Building a 6.5 Grendel Other Firearm.

Gear I use: slav.li/amazon. Channel fans and family perks: join the channel.

Keep squatting.

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9mm or 5.56 for your other firearm? Let me know.

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