Gas block posistion ?'s

[Greywuuf]

Someone please help, I have read the threads about making a model1 upper run, and it is obvious from the posts that at least a few of you have uppers with gas blocks installed in differant places. I am VERY interested in where they are. I am turning a blank barrel and am trying to place my gas system. anyone that could post the dimensions of their weapon either "pistol" gas block placement or standard from the front of the receiver to the rear edge of the Gas Block would earn my undying gratitude an respect. They would also help get another member up and running so that he ( me ) can share usefull info. Thank you , and I am sorry about the double post ( I posted a similar request in ar topics but got no response) I just think it will get more exposure here.

Thanks
Dan

[Triggerf16]

Try going to www.AR15Barrels.com

They have some information on barrel contours and gas block position.

Heck, just order the proper barrel from them. They have .300 Whisper experience and build 16" barrels in the right twist with the correct gas block.


Trigger

[Greywuuf]

I apreciate the heads up, but I have been there, and though they show the contours they do not indicate the gas block placement. In all of his writing he only refers to carbine and pistol, placement. that is exactly what I want to find out .. what IS carbine and pistol length. as far as purchasing a barrel, I plan on doing that several times.. that does not change the fact that I have a blank that I want to use on an AR. I have a lathe and a liscence to work on other peoples guns as well as my own. what I dont have is a dimension to build to.

thanks
Dan

[Triggerf16]

If you look at the following diagram from Randall at AR-15Barrels, you can deduce the port position.


http://www.ar15barrels.com/prod/med.shtml

I have a photo Randall sent me of my barrel in production, and the pistol port is located just forward of 4.5" from the breech end of the barrel. Take the gas block, slide it onto the barrel until it is 4.5" from the breech end of the barrel (not including the barrel extension) and see how far down the barrel you will have to drill the gas port in order to have it line up with the gas port in your gas block. My guess would be close to 5.25" from the breech end of the barrel.

On a 16" barrel, this gives 10-11 inches of travel/time while the bullet is still in the barrel, but past the gas block, and allows adequate gas pressure to actuate the bolt carrier. If the distance from the port to the muzzle is too short, the bullet leaves the barrel and the gas pressure drops before the gas system has had enough pressure and time to fully actuate the bolt carrier.

Does this answer your question?

Trigger