Calling the AR market crowded is a colossal understatement. America’s rifle is undoubtedly the most popular rifle on the market. It can admittedly get a bit boring to talk AR, but occasionally something cool pops up.
A couple of years ago I got my hands a Garrow Arms .17 HMR upper receiver. Not only is a .17 HMR semi-auto AR-15 cool, but Garrow Arms didn’t settle for your standard blowback operation that most companies use for rimfire rounds. They designed a gas-operated, direct impingement rifle that’s roller delayed.
Roller Delayed Design
The rollers are built into the bolt carrier group and are essentially ball bearings. They lock into the proprietary billet upper receiver. The purpose of using the roller delayed system over a blowback system is twofold.
The first is safety. Blowback rimfires have a higher potential of firing out of battery, especially if maintenance isn’t kept up. If a .22 LR fires out of battery it can be bad, but if the .17 HMR fires out of battery you have a much more powerful round that’s considerably more dangerous.
The roller delayed system ensures the firing pin doesn’t contact the cartridge until the bolt is fully closed.
The other reason for this design is for reliability. The variances between rounds and pressures make it difficult to design a semi-auto system that works with every round reliably. The roller delayed locking system ensures the pressure is consistent and the gun cycles reliably.
The lightweight bolt the Garrow Arms upper uses also minimizes movement during the gun’s recoil. The .17 HMR round doesn’t produce a lot of recoil by any means, but the lower recoil here means less scope movement when sighting onto a small target which makes follow-up shots quicker.
Specs and Installation
The Garrow Arms Upper utilizes an 18-inch stainless steel barrel. The barrel is threaded with standard ½ x 28 threads. I tossed on an oversized flash hider from a now-defunct company because I had it lying around. However, it’d be great with a suppressor, especially when hunting.
The round handguard is textured and plenty comfortable. As you’d imagine it’s free-floating as not to affect accuracy. There are now an M-LOK rail available for the upper as well.
The upper works with any standard lower receiver and drops in easily enough. You do have to install the proprietary buffer spring, though, that ships with the upper. The buffer goes into the tube backwards, going in before the spring. The spring follows and then a plastic cap acts as your new buffer.
The 10-round proprietary magazines are the same size as your standard AR magazines in terms of width. This allows them to function in any standard AR lowers. You get two magazines with the upper and additional mags are $25. The magazines are a translucent polymer and work well.
When cleaning the Garrow Arms upper you must remove the bolt slowly because the ball bearings that act as your rollers will pop right out. To reinstall, press the gas key rearwards and carefully insert them into the bolt.
The bolt is incredibly lightweight and the design allows for easy cleaning. A quick wipe down and some Hoppe’s and you’re good to go.
The Garrow Arms Upper is compatible with aftermarket triggers, too.
I mounted my Nikon ProStaff 5 on the Garrow Arms Upper and hit the range. After a quick re-zero, I started shooting at 50 yards and eventually moved back to 100 yards. I’ve had the gun for two years now and it shoots like a dream, like a flippin’ laser beam.
The rhyme was unintentional, but the results are not. The Garrow Arms upper can create very tight groups. I’ve sent 10 rounds through a single hole at 100 yards. The upper is easily sub-MOA and in the prone position, my larger groups are about .75 inch.
I’d imagine a shooter with better shooting skills than I could produce a half-inch group with little difficulty. This level of precision makes it a lot of fun to shoot. If you need a confidence boost the .17 HMR upper will do it. It also makes it a lethal hunter that will give you the ability to score headshots with ease on small game and varmints.
It’s perfect for hunting squirrels and rabbits, and I’d imagine it’d be a fun gun for taking out prairie dogs in quick succession.
As you’d expect, the GFD AR17HMR Upper turns an AR-15 into an incredibly soft shooter, ideal for smaller and young shooters.
.17 HMR ammunition isn’t as cheap as .22 LR but the Garrow Arms upper is still a great teaching tool for new shooters. It will devastate soda cans, spinner targets, and more. The only way to make it better for new shooters is to put a suppressor on it to make it even more comfortable to use.
Reliability wise the gun runs and runs. You’ll experience the occasional failure to fire due to the nature of rimfire rounds, but they are few and far between. The single stack magazines load easily and function reliably.
The weirdest thing is reaching for the charging handle and realizing it moves considerably less than on a standard AR. Muscle memory says it should move much further back, but it takes only a very short pull to load the gun. All other controls work as they do on any other AR-15.
The Garrow Arms GFD AR17HMR Upper is a unique addition to your AR platform with a cool direct impingement roller delayed system. It’s not just a gimmick rifle though. It is reliable, extremely accurate, and easy to handle. It’s a ton of fun, and perfect for small game hunting.
Oh, and it’s California legal, too.
Specifications: Garrow Arms GFD AR17HMR Upper for AR-15 Rifles
Barrel Length: 18 inches
Caliber: .17 HMR
Action: Direct Impingement Roller Delayed
MSRP: $750 ($599 avg retail)
Ratings (out of Five Stars)
Accuracy * * * * *
This thing is a laser. It’s quite accurate and very impressive producing sub-MOA results.
Ergonomics * * * * *
Obviously, this is an upper receiver review and the ergonomics are that of a standard AR-15, which means they’re excellent. The forend is comfortable and the charging handle is easy to reach and use. No complaints.
Reliability * * * * *
I’ve yet to encounter a failure to eject or extract, any kind of double feed, or problem whatsoever. The .17 HMR upper just works.
Customization * * * *
Being an AR upper so you can swap a few things, including the handguard and charging handle. The threaded barrel allows for all sorts of muzzle devices.
Overall * * * * *
The Garrow Arms upper receiver is a brilliantly designed conversion for your standard AR-15 lower. It’s accurate, reliable, and truly unique.