A2 site gas tube roll pin issue

[BobbyJ]

I'm having a tough time getting out what should be easy. I have an old colt AR that I wanted to snug up the barrel nut on. The barrel can be move a little by rotating it. Which then can throw off the front sight. Its just open sights standard M4 A2 front sight and old fashion carrying handle.

Rather than remove the entire sight I though just punch out the pin holding the gas tube to the front sight. Easy right? Wrong.

Unlike most A2 sights this one did not have the pin flush on both sides more like counter sunk 1/8" or so. So using 3 different 1/16" punches one starret and two other roll pin punches I tried to punch it out. Just ended up with 3 bent punches. Used oil lube etc. I'm almost thinking there was never a pin in there and like someone put a gas tube in without that drilled hole that the pin goes through to secure it. Is this possible? I can't pull it out so something is holding it.

Its not a new gun its probably 30 years old. It works fine except for barrel being a little loose, if you grab the barrel you can twist it side to side stopped by the front barrel pin. Which to me means that snugging up the barrel nut might be all it needs.

Can this be hand drilled out and just put a new roll pin in?

Or I guess I could take the entire front sight off which might not be that easy either.

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[imashooter2]

That looks like a solid pin with the end flared by a staking. Just a touch with a drill to knock off the flared end should work.

ETA: if it truly is a roll pin, don’t try to drill it.

[imashooter2]

Also take one of those bent punches and cut it short, maybe 1/8 inch before the taper to the handle. Use that to start the pin moving, then after it breaks free, use a standard length punch to finish it.

[Mk42gunner]

Also soak the bejabbers out of everything with your favorite snake oil before trying to remove the gas tube. If it has been there for thirty years, it is probably caked with carbon and will not want to come out.

Trust me, you do not want to try getting the front half of a gas tube out after it has broken at the pin hole.

Robert

[imashooter2]

It begins to seem driving out the taper pins and removing the entire sight base is the safer and easier path.

[country gent]

A lot seem to think any and all pins need locktite on them also. You may need to heat it some.

That appears to be a solid pin and may be a hardened dowel pin. Driving out the tapered pin and removing the sight and tube together may be easiest. Once its iff it will be easier to get a solid base to remove that pin

[Gtek]

Excellent advise above about making short starter punch! Also a quick spin after cut to put very SLIGHT radius on new edge to break corner will prevent gouging in ID. I thought everybody at this point would have two or three of those crooked 1/16" punches and had made starters. An extra set of hands to hold rifle and a good solid foundation to drive against would be a nice touch. One never knows how much the other knows in this online thread game, but several things can be found with a "wiggler" front end and with several scenarios getting there on that platform. The 35-80 ft. lbs. window sometimes just doesn't work out with given stack up, over tightening possibly opening up slot then backing off to hole that works is one. I have seen some things from the big names and the individual assemblers that are head shakers. When you get your pin and tube out and if not deep into this platform with something not obvious found give a shout out, I am sure there is a experienced sounding board here on this forum to help.

[Indy650]

I would just pop out the front sight pins and pull the whole assembly off but if you're determined to get it out heat is your friend. Not so hot that you might ruin the temper but 5-10 seconds with a blow torch will likely help a lot. Almost always when I have a stuck pin or something similar a little heat solves the issue. If that doesn't work you might have to carefully drill it out.
edit: with a closer look it does indeed look like someone used a solid pin and peened it to stake it in place like imashooter2 already stated. His advice might be a good option also.

[BobbyJ]

Thanks guys! Been busy not tried it since, waiting for a return (Someone always borrows me stuff) of my grinder so I can cut off one of my bent punches and give it another go.
Going to try to some new wonder penatration oil called "Free All " not getting my hopes up.

Then I have to decide to drill it out vs just taking the sight off, crushwasher. I've heard those A2 taper pins can be a pain getting out too.

[imashooter2]

Start the Kroil soak on the taper pins today same with the tube pin. A day is better than an hour, a week better than a day. Renew the oil regularly, you want it wet. Short blows with a heavy hammer are best for the taper pins. I favor a 3 pound drilling hammer with the sight base on a wood block. Brace or have an assistant hold it so the pins are solidly backed up by the wood.

[Gtek]

An observation from the past is I have also encountered the base pins being peened on backside. Over cut of taper reamer or intentional, much pin on backside was then flattened out. The "tail" was removed by some very careful grinding and a big enough hammer to move it through expansion that had occurred below surface level. Some were found so deep they were set on mill and drilled for .125" split pins. Then you may find if inclined that after removal of the base assembly where the holes transition it has scratched the poo out of barrel exterior twisting and pulling it off. Still in the beat the pin out camp from this side of the computer, if new split pin found not too loose install and stake and move on.

[BobbyJ]

Just a follow up. On the Roll punch from hell.
I gave up on it for a few months. today I went to buddies house who has nice wood working shop. I put a 1/16" drill bit in his press. Put some 10-30 penzoil in the roll pin hole and drilled away. Punched right though and the tube still would not come out. Tried to pound it with a down rod from the bolt carrier end to loosen it but it would not move forward at all (Probably was already at the end of the A2 gas block end.

I was about to just cut it out. So put a pair of vice grips on the gase tube where it meets the A2 Gas block (Thinking it would crush the tube) Turns out those tubes are pretty strong did not crush it. Just rotated the vice grips back and forth and it finally budged. OMG was like finally and pulled it out.

Looked at the gas tube and it had two holes drilled it. The hole we drilled out 1/16" and one maybe 1/8' down from it with a smaller hole 1/32" My bit nor punch would fit it so it was there before hand.
Take a look at the gas tube. I can't understand why that extra hole was even there as its too small for a roll pin and is the wrong spot if you want the gas port lined up.

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Also, does anyone know why they cut in the circular ring cut in the tube that saddle each side of the roll pin hole? I think it can be reused even with the extra hole.

[Moleman-]

Congrats on getting the pin out. The gas tube is a tube with a small rod crimped in the end to block it off and give you something solid to pin into. Those two grooves are the crimp marks. Don't know why it has the other hole other than a defect.

[Gtek]

I have ruffled the feathers of more than one "COLT FAN BOY" over the years telling him this or that was sub-par. Probably the contractors stoner nephew on a Friday afternoon part.
Well, now that we can order a new tube for that, what's going on with barrel extension in upper and timing of nut?

[BobbyJ]

I have ruffled the feathers of more than one "COLT FAN BOY" over the years telling him this or that was sub-par. Probably the contractors stoner nephew on a Friday afternoon part.
Well, now that we can order a new tube for that, what's going on with barrel extension in upper and timing of nut?

I might just use that gas tube again that extra hole drilled in it does not seem to hurt anything.

On the barrel while it shot fine the actual barrel nut was probably at 0 to 1 pounds of torque. I could take it off by hand. Even with low torque the fit was fine and actually felt tight. You would never notice shooting or handling gun. Only if you tried to rotate the barell would you notice you got roate it like 1 deg back and forth with the barrel indexing pin preventing further movement. The gas tube prevented it from unscrewing any further.

So it seems they can function from 0 pounds to 80 pounds of barrel nut torque.

I doubt that barrel nut was ever torqued to 30+ pounds. The gas tube prevents any rotation of the barrel nut.

Wonder what the ft pounds per gas key opening is on average.

Gas tube lined up = 0 ft pounds of torque
Gas tube at next opening = ? ft pounds

I read some people cant line them up and end up going past 80 pounds. I don't see how that is possible unless their starting slot is like 40 pounds and the next gas tube slot is 41 pounds higher.

[BobbyJ]

I have ruffled the feathers of more than one "COLT FAN BOY" over the years telling him this or that was sub-par. Probably the contractors stoner nephew on a Friday afternoon part.

Yea as long as you have people building them I would expect some "Built on a Friday" But I can't blame Colt because I bought it at a Gun show and I think they maybe have pulled it apart. Since it was not directly from a retailer or factory I don't really know its true history. People like to tear things apart for many reasons. I also have two newer 6920s and they have no defects or issues except one has feed ramps which I consider a bit on the rough side.
I have Aeros too, I just like that old fashion A2 (No rail) with A2 stock. I went more for the Retro Look than brand name.

[BobbyJ]

Congrats on getting the pin out. Don't know why it has the other hole other than a defect.
Its not a defect as in a imperfection in the metal. Its an actual hole drilled all the way through but with a bit smaller than 1/16".

So someone purposefully drilled that hole. The only thing I can think of is There is some uppers that have a pin in a non mill spec area and they tried to use that gas tube and failed. Why would a factory drill a useless hole through a gas tube? Would take a bit they never use for gas tubes and some idiot to drill it the the wrong spot. Just really weird.

[Moleman-]

No idea on the extra hole then. I have run across two factory DPMS rifles that had the barrel extension come loose when the owners were tighening up the barrel/handguard nut after putting FF tubes on them. The extensions hadn't been corectly torqued from the factory so they didn't need much beans to put them back in place and secure them with rocksett and a longer index pin set just below minor dia of the barrel threads.

[Mk42gunner]

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

[BobbyJ]

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

I was thinking of that too. It is like 15,000 psi, you are probably right best to buy a new one.

Why would the bend in the tube be a weak spot? They come pre bent from the factory I thought. Do you mean they wear out with time and burst at the bend?

[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]

:smile: