Rimfire ARs: Colt/Umarex AR-15 Review Greg Rodriguez March 2nd, 2010 | More From Greg Rodriguez Share0 Tweet Email Skyrocketing prices and plummeting availability of .223 ammo has led many shooters to dust off their .22s. They’ve also driven several manufacturers to produce rimfire versions of the popular AR-15. One, Carl Walther of Germany, is producing a complete line of Colt-branded rimfire ARs under license. When I heard about this, I was intrigued and ordered the Colt M4 Carbine and M16 Rifle from the importer, Umarex USA. The M4 is a classic, collapsible-stock carbine, while the M16 Rifle is a standard full-length gun. I wanted to try one of each to test the new rifles’ suitability as low-cost substitutes for my .223 ARs for at least some of my training. Outwardly, the rimfire M4 Carbine and M16 Rifle are almost identical in appearance to their centerfire namesakes. They are built on die-cast, CNC-machined receivers of high-strength aluminum that closely mimic the look of a forged AR receiver. Though the front sight appears to have an integral gas block, the rimfire Colts employ a blowback, rather than direct-gas-impingement operating system. The other differences are more subtle. First, the safety lever rotates 180 degrees between “Safe” and “Fire.” According to Walther’s Daniel Rieger, that is to keep the safety from bothering left-handed shooters. However, he did add that a 90-degree safety is coming. The other significant operational difference is that the bolt release is just for looks. The bolt locks open on an empty magazine, but you have to slingshot the charging handle to close the bolt on a new magazine. According to Rieger, this was to avoid a redesign that would have driven up the cost of the gun considerably. Internally, there are many differences between the rimfire and centerfire Colts. I don’t have the space to cover them all here, but most have to do with the fact that the guns were designed from the ground up as rimfires, rather than modifications of the standard AR platform. One feature is an adjustable bolt that allows owners to easily tune their Colt .22 to run perfectly with their favorite load, ensuring absolute reliability. [Show as slideshow] Another is the barrel design, the outer portion being a sleeve, while the actual barrel is a Lothar Walther-built tube that is fixed at both ends and floats in the middle. That keeps it under constant tension and actually stretches the barrel, which, according to Rieger, keeps it straight and is the secret to the guns’ accuracy. My test rifles were pretty standard AR-type setups. The M4 Carbine has the same stepped, 16.2-inch barrel; bayonet lug; removable carry handle; and six-position stock as my Colt 6920. The M16 Rifle is a conventional, fixed-stock gun with rifle-length handguards and a 21.2-inch barrel. Both use Walther-designed 10- and 30-round magazines of stout polymer. Overall fit and finish of both guns is excellent. I asked my friend Lance Bertolino, a police firearms instructor, to help me test the new Colt rimfires. We spent the better part of the day running the guns through our regular carbine drills. We did lots of rapid-fire work, as well as some precision shooting out to 50 yards. All tolled, we fired a total of 700 rounds of various brands of .22 Long Rifle ammo through the guns in just a few hours. Neither AR so much as hiccupped, and those three-inch Shoot-N-C stickers were in danger all the way out to 50 yards. Overall, I was very impressed with both ARs. They ran flawlessly, shot great and felt very much like my .223 AR-15s. My only issues are the heavy triggers and the operation of the bolt release. I understand why Walther designed it the way it did, but not having a functional bolt release means training with the rimfire Colt is not exactly the same as training with my centerfire gun. It won’t keep me from buying one, but I wish they could find a way to change it. The new Colts were a revelation. Neither Lance nor I would have given a second thought to training with a rimfire AR a few years ago, but they make a lot of sense in this economy. You could buy one because they’re cool or fun to shoot, but I’m going to buy one because I know that with the money I’ll save training with .22s instead of .223s, it will pay for itself in no time. What’s not to like about that? The author put the rimfire ARs through the exact same workout as he does his .223 fighting guns. Both passed with flying colors. Share0 Tweet Email Load Comments ( ) Don’t forget to sign up! Get the Top Stories from Guns & Ammo Delivered to Your Inbox Every Week Even More Show More Get the Guns & Ammo Newsletter FREE! Get the top stories delivered right to your inbox every week. 9 Awesomely Creative Ways to Kill ZombiesRead Now! Advertisement ▶ Now on Tablets! Subscribe & Save! Temporary Price Reduction! Subscribe Now Give a Gift | Subscriber Services WAIT!DON'T MISS A SINGLE ISSUE! Get 12 issues for the low price of just $9! Subscribe!