View Full Version : How to safely loosen up AR pins

03-18-2012, 4:13 PM
I have a single lower that I plan to use for both a 20" and 16" upper. The front pivot pin is a true blue PITA to push out of the 20" upper. On the 16" it won't even go all the way through.

I noticed that it operates easier without the uppers, and easiest before it gets through the left side of the receiver. This leads me to rule out the spring and detent pin as the cause.

There are no obvious obstructions when I look through the upper and lower - chips, burrs, dirt, etc. it looks very close. Should I use lapping compound to slightly open up the left side of the pivot pin hole? Of course I would do this very sparingly, and continuously recheck figment as I go.

03-18-2012, 4:29 PM
Probably the finish is a little thick in there. I've seen them so bad that a drill bit had to be used to clear the way. Then grease it like a pig.
I would take out the pivot pin and detent/spring and coat the pin with Flitz or jewlers rouge to clean up any little rough spot you find. Using the pin as the polishing tool.
1/4" drill bit should slide right through the lower upper holes to check alignment, roughly speaking.
This usually happens on "bargin" lowers.

03-18-2012, 5:34 PM
Tight is OK as long as you can knock it out somehow. Lube it up and work it hard, then don't worry about it. The gun should operate without having to take the upper and lower apart.

03-18-2012, 5:35 PM
have you tried extended take down pins with that nice extended grip surface?

03-19-2012, 7:35 AM
As long as it actually does come out, without resorting to large hammers and a brass drift, don't worry about it.

Look at the lifetime of the pin, and how many times you will realistically need to remove it. If you take it apart 3-4 times a year...who cares how stiff it is?

03-19-2012, 8:33 AM
I also have a lower/upper combo where the pivot pin was also very difficult to get in/out. Tapping it with a hammer was the only way to remove it.

Annoyed me enough that I considered reaming out the hole. Finally, after an embarrasingly long time, the solution popped in my head.

Rather than muck around with the lower, I just filed down the pivot pin till it slide home the way I wanted.

New pins are a buck or two, so if you file or sand off too much, just toss it and pick up another one.

Hit it with a sharpie or back to black when you're done and Bob's your uncle!!!!

03-19-2012, 6:01 PM
Thanks for the suggestions. I'll find that Flitz I have somewhere in the house and try that, after removing the pivot pin completely and checking alignment.

For those who mentioned not having to remove the upper, but only a few times... I did mention that I'm using two uppers on the same lower. My girlfriend doesn't like the 20" HBAR too much, so the 16" pencil is for her to use

03-19-2012, 6:06 PM
A little oil and it'll loosen up on its own

03-20-2012, 9:12 PM
Update... found the hole in the lower was machined offset. It's a Spikes lower with RRA LPK.

I removed the pin, detent and spring. It goes in smoothly through either side until it meets with the other hole. Then it's a struggle. Gonna try polishing the end of the pin since it's cheap to replace if I ruin it or it doesn't fix the problem.