TFB Review: 2,500 Rounds On The H&R 635 9mm Subgun

Few guns exude as much 1980s-ness as the Colt Model 635. It was the perfect encapsulation of a timeframe, taking the Vietnam veteran M16 and adapting it for the streets of the cocaine wars. PSA sub-brand Harrington & Richardson has reintroduced the 635 as a pistol with an arm brace, and they sent one to me for review.

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Disclaimer: PSA provided this gun for review. I paid for the ammo. TFB paid for the article. This is not my first review for PSA, nor will it be my last.

Background & Features

My love for the Colt 635 SMG dates back to childhood. One of my GI Joes had a shorty M16 with a curious stick magazine that I eventually learned was indicative of a 9mm gun. Fast forward to adulthood, and the 635 still caught my attention. The gun screams “cocaine wars” like few other firearms, and some interactions with the DEA in my professional life further added to the mystique of this little subgun. I really wanted to add one to my collection.

But actual Colt 635 SMGs are extremely expensive, thanks to the regulatory structure in the United States. Semiauto rifle versions exist, but the 16-inch barrel ruins it. Clone builds were an option, but parts were expensive and hard to find for many years.

Enter the Harrington & Richardson 635 clone. H&R is Palmetto State Armory’s retro brand focused on bringing back classic and interesting firearms at price points that don't break the bank. I am an unabashed fan of this project and the PSA and H&R crew unveiled another raft of fun retro clones at SHOT Show in January. After seeing the H&R 635 at the show last year, I asked them to send one out for review.

The H&R 635 clone is a fairly faithful homage to the original Colt gun. It has a slab-side A1 upper with the enlarged 9mm deflector seen on the originals. The receiver markings mimic the original H&R ones, though these are neatly-cut laser engravings rather than a true rollmark.

Rather than a true stock and the associated regulatory paperwork, H&R includes an arm brace. From 20 feet it looks an awful lot like a true carbine stock, but it has a very skinny rear surface so as to not encourage shoulder firing. A QD stud mount sits on the back surface for use with a one-point sling, allowing the shooter to hold the gun out against sling tension.

Teething Pains

I started off my testing with some ammo compatibility testing. Blowback guns can be sensitive to differing bullet weights, though AR9-type guns don't tend to display that trait. Instead, this gun had issues with all ammunition types. Whether 115-, 124-, or 147-grain ammo was used, it had consistent failures to eject. I tried a Metalform magazine, and the issues persisted. I also tried it with a silencer to see if that improved function (once upon a time, I found that adding a suppressor to an Uzi was enough to get it to run despite not even having an extractor fitted), but the issues continued.

I took a video of the 635 cycling and observed that the extraction looked fine and there seemed to be no bolt bounce. The helpful guide on the Blowback 9 website suggested that ejector tuning was probably to blame. On inspection, the ejector was not riding at the top of the slot in the bolt as the guide suggested. Using a small torch, I warmed up the ejector and used a locking crescent wrench to gently tweak it upward. After a few tries (being careful not to bend too hard or far), it looked pretty close to the correct tuning, so it was time to test it on the range again.

On the next range outing, cycling improved, but was not 100% fixed. There were fewer malfunctions per magazine, but there were persistent malfunctions. There were also some additional malfunctions with the truncated cone design of 147-grain Winchester ammo. So it was back to the bench to tweak the extractor with a little more heating and bending. Back to the range once more, and that adjustment did the trick.

On The Range

Once the ejection was sorted it was time to run up the round count. The 635, like all Colt SMG-pattern (aka AR-9) guns, is a straight blowback design. There is no locking mechanism that holds the bolt shut during firing. Instead, the bolt rests against the chamber end of the barrel with the recoil spring holding it closed. During the firing sequence, the force of that spring and the mass of the bolt carrier and buffer act opposite to the recoil. This is not the smoothest system, but it tends to be very ammo-insensitive compared to other systems.

With that straight blowback operation, the gun cycles harder than many other 9mm guns. Where the MP-5 is refined and feels like a symphony even in full auto, the 635 is like hair metal; much louder and jarring at times but it also makes you feel alive. It is still controllable when fired with the brace extended and placed against the forearm, but if you misuse the brace and place it on your shoulder the recoil impuse is sharp.

Why would someone in the 1980s or 1990s choose this over the MP-5 or Uzi? Well, the MP-5 was and is expensive. It also has a manual of arms very different from many other guns, and lacks a last round bolt hold open. Real Uzis are open-bolt guns, which introduces more weirdness in the manual of arms, not to mention a large bolt slamming forward before the gun discharges can throw it off target. The Colt subgun offers a closed bolt platform with a manual of arms very familiar to a generation of law enforcement officers who had used the M-16 in Vietnam.

H&R provides an H&R-branded 32-round magazine with the 635. This magazine fed excellently. I also used Duramag, Metalform, and ASC magazines during the review, and all functioned well. The H&R ones tend to always be on sale for around $20 on the PSA website so be sure to grab a few extras when you buy your 635.

One noticeable difference from a standard direct impingement AR-15 is the way it heats up during hard use. On a regular AR burndown, the handguard heats up quickly thanks at least in part to the very hot gas tube running along the top of the barrel. But without that gas tube, the handguards stayed cool much longer. During burn downs it remained comfortable at higher round counts than would be the case with other guns.

About the only thing about this gun that is not fun is stuffing the magazines. I would strongly advise buying a magazine loading tool like the Lula. I use a Lula tool for my Uzi, and hoped that it might work with the 635 as well because the Colt-pattern magazines are derived from Uzi mags. Unfortunately, it did not work and I had to purchase the Colt SMG-specific model. Even though these retail for around $30, the amount of wear and tear saved on my thumbs was completely worth it.

Velocity Testing

The 10.5-inch barrel of the 635 calls for some velocity testing. Most 9mm ammo is loaded for common pistol barrel lengths of five inches or less, and moving up to twice that length can produce some interesting results. This data was collected with a Garmin Xero C1 chronograph on an indoor range at room temperature.

Most of these ammunition options functioned normally, with a few exceptions.The Winchester 147-grain FMJ ammo has a very pronounced flat point and it hung up on the feed ramp. The loads with light copper projectiles also had a few issues. But check out the velocity on the SimX45-grain ammo! A 9mm load approaching 2700 FPS is a strange sensation, and the sound was very similar to a Mk18.

Conclusion

Once I tuned the ejector the little 635 was unstoppable. I initially planned on putting a thousand rounds through the gun, but I kept seeing it in my safe, calling to me like the Green Goblin mask. It wants to go to the range and burn up your 9mm ammo, and I obliged. That’s how we ended up at 2,500 rounds on the gun.

Just like the original Colt, the H&R 635 is a rough and tumble gun from a different era. It wants to mag dump into trash. It wants you to wear a ski mask and pretend you are in Miami Vice or Bad Boys. It wants you to toss it in the bottom of your range bag with a few magazines, just in case you get bored with more serious or more academic pursuits at the range.

Don’t buy a blowback 9mm AR for practical use. There are clear reasons why the Colt subguns faded into being a historical footnote while the MP5 is still seeing use around the world. Buy the H&R 635 because it is fun. This is a gun about vibes, and it absolutely oozes them in a way that others can never match. If things got really weird and this was the gun you happened to have, it would still put in work, but that is not what the H&R is about. What it is is a gun that your buddies will remind you to bring to the next range trip. If that is what you are after, or if you also have a deep-seated love affair with the 635, just go pick one up already.