AR Roll Pin Size Question

[p238shooter]

Traded for a little used AR-15 a while back, just now had time to shoot it. Performs great in every way I expected except the trigger pivot roll pin started backing out on one side after 30-40 rounds. It is lightly snug, but a little looser than normal to stay in place.

It has an Anderson AM-15 lower, unknown trigger. The roll pin seems to be .154 inch the best I can measure it on both ends without disassembly.

Is this the normal size for the trigger roll pin or do I have one smaller than expected?

If this pin is the right size, do I need to clean the oil off and apply something like Vibra-Tite, or try to expand each side a little with a punch? Kinda hate to try the punch thing if I do not have to.

Thanks.

 

[CBarCRanch]

http://www.brownells.com/rifle-part...ammer-pins/ar-15-anti-walk-pins-prod7589.aspx

One option

 

[dennishoddy]

I'd just clean it up, and apply a little blue loc-tite. Problem solved.

 

[HiredHand]

Is the hammer spring installed correctly?

 

[SPDguns]

I'd just clean it up, and apply a little blue loc-tite. Problem solved.

Bad idea. This will make it worse.

1. If the pin in it is a true "roll" pin, it is the wrong pin.
2. You could have the correct pin but it is worn. (unlikely)
3. The pin hole in the lower receiver could be worn or enlarged.
4. If none of the above, the hammer spring could be incorrectly installed.


Where are you? I will look at it and fix it for free. PM me....

 

[dennishoddy]

Bad idea. This will make it worse. Where are you? I will look at it and fix it for free. PM me....

Yeah, I reread the op. Thought he was talking about the trigger guard roll pin being out of spec. My bad.

 

[Shootin 4 Fun]

Check the hammer spring, if installed correctly, the pin shouldn't walk. If the spring is installed correctly and the pin still walks, the best bet is JP anti walk springs.

 

[tRidiot]

Is the hammer spring installed correctly?

Check the hammer spring, if installed correctly, the pin shouldn't walk. If the spring is installed correctly and the pin still walks, the best bet is JP anti walk springs.

Almost guarantee this is your problem. Hammer spring is installed backwards, not exerting the proper amount of force on the trigger pin.

 

[p238shooter]

Ok, been away watching the game, so will try to catch up and address all the great suggestions.

I would suspect it has had way less than 100 rounds through it, so I would think wear on the pin or holes should not be a problem unless an old pin was installed for some reason. The pin was not shiny on the ends as an older one might be if it was worn and previously flopping around in a hole.

I have only pushed the pin back in to finish up firing at the range, then poked it through both directions about a 1/4 inch to measure it for the .154 inch size I posted. It has some resistance, but about half less than other pins similar I have pushed out.

I will have to do some research on the spring orientation and take a look. I am not as familiar with AR's as I would like to be, so this will be good for me to understand how it should be installed. The trigger felt as I expected for a stock fairly new unit even though the whole assembly was almost dripping with oil.

I'll take a look at the spring, if not the problem, will pick up a new pin in case this one might be odd sized and out of spec for some reason, then go from there. As a last resort, most likely a dot of blue Lock-tite or Vibri-tite would take care of the problem, had that on my might need to do list, but wanted to look at other options first. It has some resistance in the hole, just slightly less than it should.

SPDguns - I so appreciate the offer but I am about 30 miles East of Tulsa, so not real close, let me catch up on looking at the spring and putting in replacement pin, and I will post what I find.

Thanks to everyone for suggestions.

 

[lasher]

hammer spring tension holds the pin in place. be certain, as others have posted, the hammer spring is on correctly. i use KNS pin sets on all my rifles, the pins don't walk or spin