Shortest gas system in the ar

[tp555]

See the pic.This is a custom 9mm barrel with gas block and gas tube.Gas port is 1/8" in front of the case mouth inside the bore.This customer already has a 9mm barrel that cycles but the gas port is about 1/2 " from the barrel extension.I made that one also.He like to play with this.So, you can put the gas port that close to the case,but you will need custom gas block and gas tube.The handguard will have to 2"ID or have a cutout for the gas block.This is a straight gas tube and gas block is a bit higher.It can be done to any cal and you will have to sort it all out.Some people like to do that.

[Spook]

T is the nut/threading a must or will it stay in place using the set screws normally found on your gas blocks?

[tp555]

Set screws will work and it has 3.The nut is for positive gas seal in case it doesn't.Saves the shipping back and forth.Customer will get to find out.Its a prototype and his toy.

[LouBoyd]

But that's for a 9mm. Are you suggesting that will work for a 300 whisper? In a gas opeated AR-15 the pressure in the cartridge must drop enough to allow the bolt to rotate by the time the bolt carrier moves far enough to begin to cam the bolt open. A 220 or 240 grain 30 cal bullet will require a considerably longer duration and/or higher pressure curve to get it to 1000+ fps the a .357 caliber pistol bullet 9mm, 40 S&W, 45ACP, and even 5.7x28 FN AR-15s can work with simple blow back actions. I don't know if that's been done successfully with a 300 Whisper but I've not seen one.

The Desert Eagle which is also rotary bolt and gas operated puts the gas port about a millimeter in front of the case mouth., but it then has about 4" of gas tube which runs parallel to the bore to the front of the slide where a gas piston is located. I'm not saying a short gas port location can't work with 300 Whisper but there's more to the design than just moving the gas port location and adjusting the port size to get proper functioning.

Spook, I don't think the axial forces on the gas block would be significantly higher because of the short gas port location. It's important that the gas block doesn't come loose but there are many ways to accomplish that including pins, clamps, and set screws. The threaded barrel and nut no doubt works if the barrel contour allows it but I don't see it's advantage. I prefer clamped gas blocks for ease of machining and a good seal. For highest precision do you want a gas operated rifle at all?

[tp555]

Short gas system is for short barrels.The longer ones already work.This is a prototype and it will be tweaked by the customer.