Would a sheared barrel index pin bugger up the hole in the barrel extension?

[acebanana]

Long story short on my ar15, somehow after torquing my barrel nut to 80ft-lbs (at 90* to the crowfoot wrench) to get the screw holes lined up the index pin on my barrel began to shear/distort enough that the barrel rotated in the upper receiver and prevented the bolt from closing (bolt lugs hit the extension lugs). After disassembling it I noticed the pin in the extension had a little left to right play, so while I plan on ordering a new index pin I was wondering do you guys think this could have also damaged the hole in the extension? Or is the extension harder than the pin? This is a brand new barrel (I actually owned it since last summerish, just now got around to putting it together so it's past the 90 day money back) so it's not like it has wear and tear. Also the upper isn't cracked but the edge of the slot in the upper seems ever so slightly deformed so I'm not sure if it is deformed enough to warrant a new upper as well, I will have to find out once I get the new index pin. Also the index pin came right out with some pliers so it doesn't seem like it was really pressed in or anything.

Thoughts? Could I have gotten a pin that wasn't hardened correctly or something?

 

[fastbs]

I've heard of indexing pins falling out by just bumping the barrel so some apparently do not fit very tight. Had one shear off that I'm sure never got over 35 ft lb a couple weeks ago. The diameter of the pin is 1/8" so if your handy just make a pin by cutting a little off the bottom of a 1/8" drill bit. Once pressed into the barrel make sure it's not too tall and trim it down if needed. Could see if the bottom of the drill bit fits loose before you cut it. It should not have any play once in the hole.
The pin just holds everything in line while installing the barrel, so a little play may not be bad but I'm not sure about that and wouldn't be happy with it. Maybe someone else will chime in.

 

[acebanana]

Yea I mean I really hope after I put a pin in it, that there won't be any slop in the extension hole for the pin. I'm crossing my fingers that it only wiggled back and forth because it got deformed and the hole didn't get deformed. But if there is any play I'll probably have to order a new upper and hope it works after that, can't afford a new barrel right now unless uncle sam is really good to me this year with taxes.

Oh and didn't think about the drill bit, I might give that a shot tomorrow. I feel like this pin had to have been not hardened or something. Maybe if the extension hole is boogered up I can just fill it with some sort of hard epoxy and drill a new hole?

 

[Oryx]

If I'm understanding this right, you applied about 2x the amount of proper torque (35-40 lb./ft) to the barrel nut which twisted the barrel and indexing pin into the receiver and it bent up the pin and loosened it? I'm not sure if the pin was supposed to be hardened or not, but I would think if it was harder, you would have really buggered up the slot in the receiver more than described. Have you had a look at the receiver threads to see if that are damaged? I would suspect the indexing pin hole might also show slight deformation as well. I have never installed an indexing pin but would have to think that some sort of press fit rather than epoxy would be better, but like I said, not really experienced there.

Just out of curiosity, what screw holes were you trying to align? We're you referring to the gas tube hole alignment?

If you are going to have the barrel fixed, it might be worth either consulting or hiring a competent gunsmith to do it. Whatever course of action you choose,I hope you are are able to get it behind you. A good learning experience makes us all better.
I am interested in how this tuns out - good luck.

 

[acebanana]

Well the proper torque is 30 ft-lbs to 80ft-lbs including the GI armorer's wrench, so the actual torque specs are a little higher because the extra length of the GI wrench. I used my torque wrench @ 90* to the crowfoot wrench so the actual torque applied to the nut is still a max of 80 ft-lbs, or slightly less than the max torque spec.

And the holes were the screw holes in my proprietary barrel nut, you have to have them at 12 o'clock, 3 o'clock, etc. So I followed the directions that came with the hand guard that state to tighten the barrel nut to 30 ft-lbs and then go up to 80 ft-lbs until the holes are lined up, which took until ~77 ft-lbs if you want to be exact.

I don't know at what torque the index pin actually started to deform though, for all I know it could have started to deform at 30 ft-lbs.

Also I didn't mean to say the epoxy was to actually hold the pin, I meant I could use to create a straight hole if the original is deformed but to the naked eye it doesn't appear to be.

I mean all the accounts I've read of a sheared index pin no one damaged their receiver, and mine is only very slightly deformed but the threads are fine. What caused the barrel to rotate was because the pin was deformed to the point it was only 0.117" +/- 0.001" in diameter.

Thank you though, I hope it turns out well.

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[Ballista One]

And your barrel is made by whom? The fit between the pin and barrel extension is an interference fit. If you were able pull out either the pin is bad or the barrel is bad. What brand is the barrel?

 

[acebanana]

Well I didn't want to put the brand as to not hurt their reputation or whatever until they respond to my email, but it is a well known brand. It wasn't cheap though, a little more than $300 shipped. 18" SPR SS, 223 wylde chamber, 1:8 twist.

I had ordered the barrel last summer though and didn't get to put it together until now so it's past the 90 day money back.

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[acebanana]

In case anyone was wondering, I'm shipping it back as soon as all this snow clears up. They emailed me saying they would put in a new pin & check it out under warranty.

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