Back when companies were busy recalling semiautomatic rifles in .17 HMR, I was greatly puzzled by their inability to offer rifles that worked with one of our most useful rounds. Turns out the solution was in building rifles from scratch rather than trying to adapt .22 Long Rifle semiautos to the higher-pressure .17 HMR round.
And that’s essentially what Bill Alexander did in developing the Alexander Arms AAR-17. Three years of development work resulted in a mil-spec-size AR-15 upper built specifically to handle no cartridge other than the .17 HMR.
In the event of a blown case, the receiver is roomy enough inside to allow propellant gas to quickly dissipate and strong enough to contain brass fragments. On top of that, certain seemingly insignificant design features such as a slightly oversized extractor slot in the barrel and a huge bolt face are designed to channel gas away from the shooter. Those along with component parts machined Swiss-watch precise and an off-the-chart level of quality, add up to a semiautomatic rifle in .17 HMR that I have absolutely no qualms about shooting.
The lower assembly of the AAR-17 is identical to the one seen on Alexander Arms rifles in 5.6mm NATO/.223 Remington, but a number of interesting differences lurk up top.
For starters, two types of Alexander Arms AAR-17 upper assemblies are available. The base model is of conventional configuration and consists of a standard A4 style receiver with a separate, mid-length, free-floating G10 composite handguard. My test sample represents a step up in price, with a one-piece receiver/handguard and the entire upper machined from a single piece of bar stock. The flawless machining has to be seen to be believed.
During development of the rifle, high-speed video of its operating cycle revealed that ejected .17 HMR cases travel in less predictable trajectory paths than 5.6mm cases, and for this reason they require an ejection port measuring .640 inch tall. The larger port eliminated the use of the standard AR hinged dust cover.
A forward assist is not needed for the .17 HMR cartridge, so it is absent from the standard receiver. While not operational, it is on the one-piece upper because it is the same one used on rifles chambered for the .50 Beowulf.
An integral Picatinny rail measuring 15 inches long runs from stem of handguard to stern of upper receiver, and that, along with three additional eight-inch rails on the handguard section, offers enough room to accommodate about every bell and whistle in the Brownells catalog. The charging handle is pure AR-15, and the right side of the receiver has the familiar shell deflector behind the ejection port.
The 18-inch stainless steel barrel measures .800 inch at the muzzle, has six cooling flutes machined along most of its length and six-groove rifling with a twist rate of 1:10. Its A1 flash hider is machined from 4140 bar stock and then heat-treated prior to being attached to the muzzle with 1/2-28 accessory threads.
A stainless steel extension torqued onto the breech end of the barrel provides an AR-style contact flange for a threaded collar that secures the barrel to the front of the receiver. The breech end of the barrel is induction-hardened to resist deformation as the bolt slams home during each firing cycle.
If you are wondering, as I did how, they manage to reach around the barrel and through eight inches of hollow handguard to attach and tighten the barrel nut, those clever fellows at the plant in Radford, Virginia, use a steel tube with a castellated end that mates with the teeth on the nut. A snug fit between the bore of the handguard and the tube prevents it from twisting out of engagement as the nut is being tightened.
As one would expect to see on a recoil-operated AR, the chrome-plated steel bolt has neither locking lugs nor a gas key. Even so, at 11 ounces it weighs the same as a complete 5.56mm carrier and bolt.
The rimfire case is an ancient design and a fragile one at that, so an oversized, inertia-type firing pin and wide spring-loaded stainless steel extractor of the Alexander Arms AAR-17 along with a mild feed angle from magazine to chamber make its trip as gentle as it can possibly be in an autoloading rifle. The recoil spring for the bolt is wound to aerospace specifications, and it along with a buffer fit inside a recoil cassette. The cassette fits inside the buffer tube.
Moving to the lower assembly we see a six-position collapsible stock with pull lengths ranging from 10 to 13.5 inches. The left side of the receiver houses standard AR-15 controls, including a two-position safety and a bolt catch that in this case does not hold the bolt to the rear after the last round is fired (it does work when used with uppers in other calibers).
Moving to the opposite side, a push on the .17 HMR-specific mag button allows the 10-shot magazine to drop smoothly from the gun by its own weight. Since the magazine well is sized to fit 5.56mm magazines, an aluminum sleeve held in place by a set screw reduces its internal dimensions for a close fit with the smaller .17 HMR magazine.
Consisting of two acrylic halves stitch-welded together, the magazine is actually an important part of the shooter protection system. In the event of a blown case, the clip-on magazine base plate is designed to break away, allowing propellant gas and any rounds in the magazine to escape out the bottom. Some gas would also be deflected out through the ejection port by the face of the bolt.
After experiencing blown .17 HMR cases in other rifles in the past, I hope another is not in my future but if it is, this is the rifle I would want to be shooting when it happens.
The Alexander Arms AAR-17 is set up to handle 17- and 20-grain .17 HMR ammunition available from CCI, Federal, Hornady and Winchester. Regardless of the brand, the ammo burns dirty and leaves a lot of residue behind so the chamber should be dry-brushed every 100 rounds or so to assure positive functioning. A 6mm brass bore brush bent at a 90-degree angle works fine for this. Solvent and a .17-caliber brush should be used to clean the bore every 200 rounds or more often should malfunctions occur.
To avoid accuracy-destroying damage to the rifling at the muzzle, the bore and chamber of the barrel should be cleaned from the chamber end. Doing so is made easy by using a Delrin cleaning rod guide made specifically for the AAR-17 upper by Sinclair International.
A 200-round break-in session is recommended to further smooth contact points of various parts and as it is with all semiautomatic rifles, cleanliness and the proper amount of lubrication applied in the right places is important for smooth sailing.
During accuracy testing I found the mil-spec trigger a hindrance to top accuracy. It traveled through an abundance of gritty creep before finally breaking at eight pounds, and that made squeezing off each shot not only challenging but tiring as well.
I could have switched out the trigger for a target unit but doing so requires the installation of a heavier buffer (available from Alexander Arms for $25), and I did not have one on hand. I was told that reaching the exact spring-to-mass balance required of the gun is essential and decreasing hammer mass and spring force by installing a lighter trigger without installing the heavier buffer can cause excessive bolt speed, which in turn plays havoc with fired case ejection. If I were to order one of these rifles I would most definitely specify the Alexander Arms or Jewell target trigger.
During my accuracy tests I did experience a couple of smokestacks, but they were quickly cleared. With that program out of the way I squeezed off 200 rounds as fast as I could aim and pull the trigger. Accuracy suffered very little from an extremely hot barrel, but I did experience two cases that split from the mouth to about a third of the way back on their bodies. Neither caused a malfunction, and a bit of smoke flowing out the ejection port caused harm to neither rifle nor shooter.
I had several stoppages during the rapid-fire session when the hammer followed the bolt to battery rather than hanging back and waiting to be released by a squeeze on the trigger. Manually cycling the bolt quickly got the rifle back into action.
My only explanation for this is I got lazy and allowed the rifle to run a bit too dirty. Giving the rifle a good cleaning eliminated the issue. There were no jams inside the action, but if one was to happen it would be nice to have a bolt catch that can be manually engaged to hold open the bolt during clearing. The standard AR-15 catch is there but it is inoperable with the AAR-17 upper.
Magazines proved to be easy to load, even on the 10th round. Cartridges fed from it to the chamber like silk on silk.
The AAR-17 is available as a complete rifle or the upper assembly only. An instruction book included with the latter explains how to install it on any good mil-spec lower. Don’t buy either expecting to save money due to the lower cost of .17 HMR versus .223 Remington because it is so much fun to shoot you will likely find yourself banging away every single dollar in your savings account.
- Type: blowback-operated AR
- Caliber: .17 HMR
- Capacity: 10+1
- Barrel: 18 in., w/six-groove, 1:10 twist rifling
- Overall length: 36.75 inches
- Weight: 7.25 pounds
- Finish: black matte
- Stock: six-position collapsible
- Sights: none; Picatinny rail for sight mounting
- Trigger: mil-spec, 8 lb. pull; optional target trigger available
- Price: $1,648 (as tested); standard rifle, $1,175; standard upper only, $725
- Manufacturer: Alexander Arms
- Smallest avg. group: 17 gr. Federal TNT—1.04 in.
- Largest avg. group: 20 gr. CCI Gamepoint—1.49 in.
- Avg. of all ammo tested (6 types)—1.33 in.
- Notes: Accuracy results are averages of five five-shot groups fired at 100 yards from a sandbag rest after a 200-round break-in.