Q: How does it work?
A: The AR-17 HMR is the first gas operated rim-fire. It operates with 2 roller locking balls similar to a Heckler and Koch G3.
Q: How do you get a gas gun to operate with such a small cartridge?
A: Though the design is similar to a G3 the operating principle is completely different. The GFD AR-17 HMR, rather than using the bleed-gas to operate the bolt, uses it to disconnect the lock, similar to a sear on a trigger- to allow a delayed blow-back type action at a much lower pressure. [Patent Pending # 15/008,930]
Q: How much velocity is lost with the gas system?
A: Our measurements show an average velocity loss of 25 feet per second which is less than the variation in velocity between individual cartridges from the same lot.
Q: How accurate is the GFD semi-automatic?
A: We have 50-yard targets with 10 round groups well under 1/2”. As accurate as many bolt guns of the same caliber. One of the reasons this is possible is that the lock-bolt mechanism makes compensation for differences in rim diameter during lock up.
Q: Can the 17 HMR cartridge be dangerous in an auto-loading firearm?
A: Other manufacturers have had problems with semi-automatic actions using 17 HMR cartridges. The issue lies with them being blow-back style. This would work if the pressure was consistent between rounds. A problem can occur when small differences in powder or priming compound generate different volumes of gas pressure. Dirty actions, rough chambers, and other issues can occur making it difficult to create a bolt light enough to cycle consistently yet heavy enough to stop a “hot” round from blowing its rim. The GFD solution is to lock the bolt until the pressure has dropped to a safe level. This allows for a much lighter bolt that makes faster follow up shots possible. The GFD also prevents the firing pin from making contact with a cartridge unless safely locked in battery.
Q: When I pulled the bolt out for the first time two steel balls popped out of the action. Can I use the rifle without them?
A: NO! The GFD is a high-performance rifle the roller balls are vital to the function. Attempting to operate this way voids the warranty and can result in personal injury. The roller balls are uncaged to get the best performance. They can be tricky to install the first few times (see Operator's Manual for instructions).
Q: How often is cleaning the GFD recommended?
A: Cleaning is recommended every 100 rounds.
Q: Is there a good supply of magazines?
A: Yes! Our magazines are made in the USA by Black Dog Machine are reasonably priced and can last for thousands of rounds.
Q: What aftermarket triggers can be used with the GFD and are adjustments to the buffer system necessary?
A: Though we haven't tried every trigger on the market every one we have tried works great without adjusting the buffer system. Using a precision trigger is a good way to take advantage of the accuracy potential of the system.
Q: Will I be able to change out the fore-end?
A: Yes! The GFD upper is threaded to accommodate a standard barrel nut. Many aftermarket fore-ends would be a direct replacement. However, on the GFD the gas block is fairly close to the chamber end of the barrel and some fore-ends with longer barrel nuts will need to be modified to work properly. Someone with Dremel tool skills will have no problems.
Q: Will you be making this in .22 Magnum?
A: We are testing....
Q: Would I be able to shorten the barrel to 16” for a handier rig, or make a pistol?
A: The GFD system is designed to take advantage of the velocity of an 18” barrel using the 17 HMR cartridge. Shorter barrels start losing velocity quickly and may not function without opening up the gas port; if at all. The barrel is recessed in the upper receiver so has the footprint of a 16.5" barrel.
Q: Can I use a suppressor where legal since the barrel is threaded?
A: The barrel is threaded to attach a flash hider, muzzle brake, or a suppressor. You may need to install an adjustable gas block to prevent any over-gas issues. Reports are in that no adjustment to the gas system is necessary to date.
Q: Can I use an A-2 type clamp on a handle to practice high power rifle on the GFD Upper? My pistol range won't let me use centerfire rifle.
A: Yes! The barrel is .700 diameter at the muzzle. Use a clamp on triangle type front site from Troy, Midway, and others. You will also need some .025 shim stock to fill in the difference in diameter (I have heard a beer can works well).
Good to practice in the winter.
Q: Is the rim-fire GFD AR-17 HMR Upper legal in my State?
A: Many state laws pertain only to center-fire modern sporting rifles and have different standards for rim-fire. GFD only sells uppers at this time and can be shipped anywhere in the USA. Please consult your State or legal representatives for precise legal details in your area.
Q: Do I need to go through a firearms dealer to buy the GFD AR-17 HMR Upper system?
A: The GFD Upper is not a classified as a firearm we can ship directly to our customers.
CRPA: Is My Rifle an Assault Weapon?
Here's a link to the CRPA's reference guide on what makes a rifle an "assault weapon" in California and how rimfires (like ours) are exempt!