New Barrell - Gas Cylinder Issue

[mdoerner]

Hi All,

I have a new .308 barrel for a Garand. The diameter of the barrel at the gas port on the new barrel is 0.610", and I can't get the gas cylinder on by hand. My old barrel (which is a SNUG fit, and need a plastic mallet to tap on/off)) is 0.605" diameter at the port. I don't have a lathe or know a buddy that has a lathe, so I'm wondering if draw-filing or sanding would be more appropriate to deal with the oversize new barrel. Or is this a case of simply "getting a bigger hammer" with a wood block so the gas cylinder WILL fit....

Not knowing the milspec for the diameter of the barrel at the gas port doesn't help either, any suggestions? DOH! Lemmie see if this is in my Kuhnhausen book too....

Mike Doerner

[mdoerner]

OK, got the micrometer out. The new barrel is 0.600" on the money, my old barrel is 0.599". I see the spec in Kuhnhausen's book is 0.600" ID for the gas cylinder, +0.001" tolerance. Maybe I just have a tight barrel/cylinder combo here? The splines on my barrel come up to 0.125" on my calipers (but that's only 0.001" over spec, so I don't think that's an issue).

Short of start banging away with a gas cylinder, is there anything else to check here?

Mike D

[Ping Sr.]

.005 interference fit. Tried hand polish with a strip of very fine emory cloth?

If taking back apart isnt a concern, put barrel in freezer, gas tube in oven around 220 degrees. I dont recommend that method.

[Mark in Rochester]

Mike

These dimensions are from "RIFLE, U.S. CAL .30, M1: DIAGRAMS & PICTURES"

Eric Nicolaus

Barrel Dwg # 6535448

Dia at port 0.06000" +0 / - 0.0007

Gas Cylinder Dwg # 6535449

Dia. 0.600 +0.001 /-0

So by these drawings the tightest fit would be line to line and max clearance would be 0.0017 inches

Send the barrel back unless you have a very Big Hammer

[Mark in Rochester]

OK, got the micrometer out. The new barrel is 0.600" on the money, my old barrel is 0.599". I see the spec in Kuhnhausen's book is 0.600" ID for the gas cylinder, +0.001" tolerance. Maybe I just have a tight barrel/cylinder combo here? The splines on my barrel come up to 0.125" on my calipers (but that's only 0.001" over spec, so I don't think that's an issue).

Short of start banging away with a gas cylinder, is there anything else to check here?

Mike D

you could try cooling the barrel and heating the gas cylinder to see if it will assemble

[Clark Howard]

Get a small container of layout fluid at the auto parts store. Coat the barrel from the muzzle to the gas hole pad. Slip the gas cylinder in place. When it will go no further, give it a few good raps with a soft hammer or block of wood. The point of interference will disturb the layout dye. If it is not too great, a Dremel tool with a cutoff wheel will provide clearance. Then repeat. Good luck, and Regards, Clark

[Dean-DGR]

The best thing that can happen to your rifle is a tight gas cylinder. I make a tool for driving gas cylinders on that can be seen at http://dgrguns.com/0-main-page-tools.htm

You should never be able to fit a gas cylinder on by hand...Dean-DGR
www.dgrguns.com

[JimL]

It will never get tighter than it is right now.
Try to get it assembled and fire it.

[mdoerner]

The best thing that can happen to your rifle is a tight gas cylinder. I make a tool for driving gas cylinders on that can be seen at http://dgrguns.com/0-main-page-tools.htm

You should never be able to fit a gas cylinder on by hand...Dean-DGR
www.dgrguns.com

Well, I've got two CMP Garands that say otherwise..... One needs a plastic hammer to get off, the other slips off very easily (yes, I need to peen the splines on that one.) I'll try fitting the gas cylinder once my barrel vice shows up, after I've installed the barrel.

Thanks for the info guys. I think I can work this out, just takes a bit more effort.

Mike Doerner

[mdoerner]

Well, I've got two CMP Garands that say otherwise..... One needs a plastic hammer to get off, the other slips off very easily (yes, I need to peen the splines on that one.) I'll try fitting the gas cylinder once my barrel vice shows up, after I've installed the barrel.

Thanks for the info guys. I think I can work this out, just takes a bit more effort.

Mike Doerner

DOH, I need to fit the gas cyl to install the barrel. OK, when my vice shows up I'll get it on then.

Mike D