Relief grind on gas tube

[Alan Waters]

Does anyone know why the bolt end of the gas tube has the relief ground into it?

[98Z5V]

Flex in the barrel system? It's flared, too, in diameter, before the taper down.

The gas key on the BCG body is also chamfered.

 

Big batch of them, shows it quite well.

Edited December 22, 2018 by 98Z5V

[98Z5V]

Just measured 0.181" on the inside of a gas key on a BCG, and 0.179" on two different gas tubes, at the widest point on their ends.  A 0.002" fit for the gas pressurization needed, on two pieces that are slamming together from inches apart, with violence, isn't too bad.  Just my opinion. The taper on both pieces makes sense, I think, considering that.

I fit piston ring end gap for piston rings in engines at 0.004" per inch of bore, on normally aspirated engines.  Up to 40% more ring end gap on turbo engines.  For piston-to-cylinder clearance, I go for 0.003" in difference.  They make power.  Same kinda thing here.

Edited December 22, 2018 by 98Z5V

[survivalshop]

The Gas Tube flops around with the Barrel when shooting , so it is a good idea to have the Carrier Key & end of the Gas Tube chamfers/tapered . Good guidance of reciprocating components .

[98Z5V]

303 Stainless.  Don't fall for anything less.  Seeing lots of 304 stainless gas tubes being offered now - don't believe the hype on that shiit.

303 doesn't work-harden with heat - that's the very reason that 303 is the spec for a gas tube. More sulphur in it than 304. 

But whatever.  Buy whatever you want, from whatever vendor you want.  No matter what the quality.  Or price. It's just a gas tube, right?...

Off this gas tube soap box now...