A2 site gas tube roll pin issue

[nicholst55]

While you could possibly reuse that gas tube, with as cheap as they are and the fact that it has a couple of issues (the extra hole and more importantly to me the deformation of the tube) I would use a new one.

The extra hole would be blocked anyway and has caused you no issues in the past. The bend/ crimped section may be a weak spot and cause it to break.

Robert

^^This^^. Gas tubes are cheap. Why screw around with a damaged/subpar one?

[Gtek]

If it were me, new tube and a fit check is required and many need a tweak to engage the gas key correctly. The TM shows Shell 33 grease to be applied to external extension and external threads of upper and torqued to 35-80 FT LBS. If this cannot be achieved for tube alignment since nut not easily removed is to lap face of upper which is a match conditioning check or need on a high end build. Required material is removed to achieve proper torque value on assembly.

[BobbyJ]

If it were me, new tube and a fit check is required and many need a tweak to engage the gas key correctly. The TM shows Shell 33 grease to be applied to external extension and external threads of upper and torqued to 35-80 FT LBS. If this cannot be achieved for tube alignment since nut not easily removed is to lap face of upper which is a match conditioning check or need on a high end build. Required material is removed to achieve proper torque value on assembly.

Thanks a ton guys for all the great suggestions. I listened and got the new gas tube.

I finished it today. Drove to a local shop got a CMG Carbine gas tube very close to mine. It actually fit looser had to put electric tape on the gas tube and and barrel to prevent it from rotating after the first roll pin hammer hit, worked great.

I was expecting a major struggle with the pin. I've had some pins in the past that require more hammer wacks this one since it came with the tube seemed more of a jewel fit. Very easy and smooth, but I did cheat using a roll pin starter tool

I also finally replaced my broken door spring, thought the E-clip on the rod would be tough but using two small screw drivers it popped off first try. Must be my lucky day, was expecting a fight with that door spring.

The barrel does not wiggle any more tight, very solid now. And the BCG gas key has zero bind or touch and bolt slides in and locks up like new.

The hardest part putting it back together was indexing the gas key. My vise/table is about good to 50 pounds of torque before the table starts to want to move. At 30 ft pounds it was just past being line up, set the wrench to 50 ft pounds and the next slot lined up pretty good but the gas tube was touching one side.

So I went a bit further and OOOPS over shot it. I was not able to loosen it without extra hands, my wrench kept poping off. Had my kid push down on the tool so it would not pop out and put some weight into it. It seems 2x harder to loosen a 55 ft pound barrel nut than to tighten it to 55. Yes I used the anti seize grease.

I would guess each slot past 30 pounds = 30 pounds per slot. I was at 30 pounds and over shot by a tad, the next slot was 25 pounds higher.

Super happy my favorite AR back in service. Something about the old Retro A2 Carrying handle and rifle stock I love. I have picatinny carrying handles on the newer 6820 Colts but they are not the same, smaller harder to get fingers in.
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Instead of using a upper clamshell type clamp I tried this Wheeler Engineering Action Rod.

No torque is applied to the soft aluminum upper it locks into the bolt and upper gas key. Did not know what that rod was for at first. Its to hold the all the C-clip and washer in alignment while you torque the barrel nut. Without it its difficult to see if its lined up with the gas tube. The rubber O-ring makes it so you can keep the end of the gas rod just under the barrel nut teeth but not so low that the delta ring/snap ring and weldon spring gas slots rotate out of place.

I just mount it vertically in a wood vise and drop the upper over it and lock it. Works great.

[Gtek]

Sounds like you are good to go. For a real feel, remove BCG and remove the bolt assy from front end. With charging handle in place, install naked BCG and put your pinky in the back of group. Slide it in and out that way holding upper in normal position nice and slow. If you feel a hard bump remove hand guards and side load tube to get feel of slick. If thumb bending needed just insert tip of tube in key and tweak in opposite of bump using hole in upper as shoulder and tweak between center bends. This is one of my little things that I obsess over but if it is off, wear to internal of upper and tube and key will be wiped in short order.

[BobbyJ]

Sounds like you are good to go. For a real feel, remove BCG and remove the bolt assy from front end. With charging handle in place, install naked BCG and put your pinky in the back of group. Slide it in and out that way holding upper in normal position nice and slow. If you feel a hard bump remove hand guards and side load tube to get feel of slick. If thumb bending needed just insert tip of tube in key and tweak in opposite of bump using hole in upper as shoulder and tweak between center bends. This is one of my little things that I obsess over but if it is off, wear to internal of upper and tube and key will be wiped in short order.

Yea good idea. I just visually watched the lugs go in and also felt if there was any binding of the gas key. Really did not feel anything until lock up. Wanted to make sure they lugs were not hitting the openings off center. The old gas tube has a little bit of binding but might have bent it pounding on it to loosen it. The new one seems to get the gas key dead center.

[Gtek]