Unicorn Gas Tube Needed

[jtallen83]

So I'm trying to build a pistol with a Sig P716 12.5 inch barrel. My measurements from the gas port tell me I need a 10 7/8 inch long gas tube to make this work and I have not seen anything close except a reference to an Armalite super SASS carbine length tube at 11 inches. I'm afraid the 11 3/4 inch for a mid-length will be too much. If anyone has a source for something close to this odd length tube please let me know. Push comes to shove I'll just have a spare barrel for my 716. On a side note the port in this barrel is .071, might help explain why my 716 has symptoms of being under gassed.

[98Z5V]

White Oak Armament, brother.  You'll have to call them.   309-376-2288  

[jtallen83]

9 minutes ago, 98Z5V said:

White Oak Armament, brother.  You'll have to call them.   309-376-2288  

I was just looking at their gas tube page thinking someone has to be custom making some of the lengths they sell, they will get a call Monday. Hope they can help, too nice and too cheap a barrel to give up on. The shoulder at the gas block is way off but the dimple jig makes gas block alignment foolproof. If they can make it I may have them make a few and then grab more of those $79.99 Sig barrels.

Edited July 1, 2018 by jtallen83

[jtallen83]

@98Z5V I  used the center of the cam pin cut out in the upper to determine the 10 7/8 inch length, that should get me what I want won't it? Would I be better fudging a little to the short side then opening up the port if I need more gas? I don't want to custom order a tube only to have the tube bottom out in the carrier key.

Edited July 1, 2018 by jtallen83

[98Z5V]

4 minutes ago, jtallen83 said:

@98Z5V I  used the center of the cam pin cut out in the upper to determine the 10 7/8 inch length, that should get me what I want won't it?

That'll be perfect.  From center of cam pin cutout, forward to gas port hole in barrel.  + one more dimension.  Pick up a standard gas tube off anything, and determine how much longer a gas tube is to it's end, after it's gas port.  Those two numbers together will give you an exact length measurement that will work like a champ.

Hold on - I have one right here - measurement coming right up.

That additional length,from gas port in the gas tube to the end of the gas tube is 0.600".  Add that to the distance of: center of cam pin cutout to center of gas port in barrel, and you'll have it perfect. 

Edited July 1, 2018 by 98Z5V

[jtallen83]

Gas tube ordered, went with 11 inches after a little more precise measurement. $35 from White Oak Armament, expensive for a tube but with the price of the barrel being so cheap I am still ahead, as long as this works!

[jtallen83]

These guys are fast! ordered at about 1000. Got a call to confirm the order about 1330, very good customer service, he went over exactly how I got the measurements and what I was building so he would be on the same page. At 1545 I got the tracking number! I may just get to mock this thing up before heading back to work.

[98Z5V]

That's very damn awesome, right there. 

[jtallen83]

Gas tube is a perfect fit, dead center of the cutout. Just ordered the Aero 9 inch rail, hopefully the tube makes it past. Had bought a cheap rail local but the barrel nut blocked the tube from passing into the upper, had a spare nut from a MI rail and the tube just barely made it in, as long as the Aero nut doesn’t have any more meat than it I will be good. 

Next trip home I will start a build thread, CDNN still has a pile of those 12.5 inch barrels, with the SB3 “brace” you can make a nice 308 pistol about as close to a SBR as a guy can get. 

[98Z5V]

NICE!!!   I love it when a plan comes together...