A roller-locked gas operated .17 HMR AR15 upper? You have my attention. Garrow Firearms Development is announcing the availability of a complete upper receiver group for the AR platform that allows for the use of all milspec triggers. At a reasonable $599 price point, semi auto .17 HMR is within reach.
I recently had the chance to experiment with suppressing the .17 HMR cartridge with the Bowers Group USS 22 from Silencer Shop. And I was pleasantly surprised – the hot little rimfire round obviously was supersonic, but the crack of the bullet was much farther forward of my shooting position in comparison to a supersonic .22LR. In my opinion, the Bowers USS is probably the quietest silencer for .17 HMR currently on the market.
Let’s take a look at the Garrow upper:
The GFD AR 17 HMR fires from a gas operated locked bolt system eliminating the dangers of blowback actions. It is designed to prevent the firing pin from hitting the cartridge unless the bolt is locked in battery an important safety feature.
Why is it gas operated?
The 17 HMR cartridge is a popular rimfire round. It is made on high speed machinery producing millions of rounds each month. Vendors supply cartridge cases, bullets, powder, and priming compound to manufacturers which can have lot to lot variations. It is a small capacity cartridge so small variations in manufacturing can make a big difference. As an example a 1/10th grain difference of priming compound can vary pressure. The result can be that most of the cartridges fall under a bell curve within manufacturing tolerances and some pressures will be outside.
Blowback actions can be unreliable since the bolt needs to be light enough to operate at the lower extreme spread yet heavy enough to keep the case-head from separating with a hot round.
How does the GFD 17 HMR Upper Assembly address these blowback problems?
The GFD Uppers are designed too leave the bolt locked until the bullet passes the gas-port in the barrel releasing a small volume of gas to unlock the bolt when the pressure reaches a safe level.
GFD built in safety features:
• the firing pin can not reach the cartridge until the bolt is locked in place
• in the even of a case-head failure the gas is designed to escape down and out through the magazine well. Remember, safety eye wear and hearing protection are always recommended.
GFD AR-17 HMR benefit features:
• since the GFD Upper Assembly does not depend on inertia to operate a much lighter bolt is used allowing for a more forceful extraction cycle
• the GFD lighter bolt makes for a more stable firing cycle since there is less recoil impinging your sight picture than with a heavier bolt
• it has a patent pending gas operated design that is simple and reliable making it one of the most advanced rimfire on the market