My brother in law has a Tig welder and I want to unitize my gas cylinder. I was lucky enough to get a rifle that didn't need the gas cylinder shimmed. the gas block starts to snug up at the 4 oclock position and is plenty tight when snugged down. So with this being said, if i can do those welds on the gas cylinder without taking it off then there is no need for me to break my flash suppressor off. It is spot welded on. Also i have looked at a series of pics where the welds go and i see a good portion of the NM ones have the welds on the top and bottom. Is this good?
Do i have to take the gas cylinder off to unitize it?
- Thread starter rci2950
- Start date
I used to offer this service and it's important to follow these steps.
Yes... you should absolutely remove the assembly from the barrel.
It is recommended to use a heat sink .... in our case , a fellow made me a brass unit that was turned on a lathe to fit the gas system parts onto and a plate and bolt at one end to tighten everything up and a squared off other end for clamping in a vice for welding in position.
The cylinder is allowed to cool, wrapped in leathers for 45 minutes after welding.
for chinese cylinders, a chromoly blend filler rod and for usgi , 416 stainless or similar.
welds go at precisely 10, 2 and 6 oclock in 3/32 fillet , 1/8inch to 3/16 long. Your welder should get all that.
LOL probably doesn't matter much man.
It's a solid guide for the locations though.
I've seen some scary unitizing attempts where people have come up with thier own ideas.
I've seen a bead right around the top in a big 1/2 circle .... cylinder warped on that one and was a real ##### to get off buddies rifle.
I've seen the chrome lining of barrels flaking off around the gas cylinder region from guys trying to do this themselves, on the barrel and with the wrong equipment.
I've seen so much penetration from the on the barrel method that the assemblies where permanently welded in place on the barrel accompanied by ruined chrome lining...
My welder and myself went thru several barrels and assemblies before picking the machine and method he uses for this job. It's not rocket science at all but to get a professional result it's best to follow some pretty basic instructions like what I outlined above.
TIG welding is an art form and while some folks prefer the screw n glue unitizing method, TIG weld unitizing, if done right, should not cause any heat distortions in the cylinder and should last many thousands of rounds without failing.
One thing that's a good idea that I don't often see mentioned:
The barrel band top opening is made with virtually no clearance to the barrel journal. Where the barrel journal meets the barrel shoulder, manufacturers often undercut this area, so the band has a tendency to not center perfectly, it can end up slightly into the undercut, preventing the unitized assembly from ever coming off the barrel again.
My welding jig is made from an old piece of barrel, but I've lathe cut the jig's barrel journal shoulder at an angle so the band somewhat self-centers when my welding jig is tightened. I also open up the barrel band rear opening with a tapered sanding drum by a few thou so that it is larger diameter than the rear gas cylinder band. This prevents the band from binding on the journal undercut once unitized.
Yes, I learned all of this the hard way - lol.
The barrel band top opening is made with virtually no clearance to the barrel journal. Where the barrel journal meets the barrel shoulder, manufacturers often undercut this area, so the band has a tendency to not center perfectly, it can end up slightly into the undercut, preventing the unitized assembly from ever coming off the barrel again.
My welding jig is made from an old piece of barrel, but I've lathe cut the jig's barrel journal shoulder at an angle so the band somewhat self-centers when my welding jig is tightened. I also open up the barrel band rear opening with a tapered sanding drum by a few thou so that it is larger diameter than the rear gas cylinder band. This prevents the band from binding on the journal undercut once unitized.
Yes, I learned all of this the hard way - lol.
