Rear takedown pin is rubbing my upper

spoon059 · Sep 27, 2020

I have assembled several lowers using PSA lower parts kits and they are usually fine. The rear takedown pin in this particular lower protrudes ever so slightly and binds on my upper assembly and is a bear to remove. It has acquired off the anodized coating on the upper and requires a decent amount of force to separate the upper and the lower.

Any suggestions on what went wrong and how to fix it?

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Skipjacks · Sep 27, 2020

EDIT- Nevermind what I originally wrote. I read it backwards...thought the hole for the pin was the problem, not the pin itself.

3paul10 · Sep 27, 2020

I have bought several uppers lately, all from the same vendor, and the pin holes are out of spec and dont line up with my other known correct lowers....just like 2013 shit...

GolfR · Sep 27, 2020

Looks to me like the pin itself is the problem. It should be flush with the inside edge of the lower when pulled all the way out. There are a lot of crappy small parts out there for ARs. It’s nearly impossible to judge the quality. I would find a set of extended pins since they are easier to use anyway and give them a shot.

One other thing to make sure of is that you put the little metal plunger in before the spring for the pin retention. If you just have a spring it might be getting bent up where it slides on the pin and prevent the pin from pulling the whole way out.

spoon059 · Sep 27, 2020

3paul10 said:
I have bought several uppers lately, all from the same vendor, and the pin holes are out of spec and dont line up with my other known correct lowers....just like 2013 shit...

The pin hole is fine, but the pin itself is protruding ever so slightly into the opening. I've already staked the castle nut, so I don't really want to take it apart and try to assemble it again but it looks like I don't have much of a choice.

GolfR said:
Looks to me like the pin itself is the problem. It should be flush with the inside edge of the lower when pulled all the way out. There are a lot of crappy small parts out there for ARs. It’s nearly impossible to judge the quality. I would find a set of extended pins since they are easier to use anyway and give them a shot.

One other thing to make sure of is that you put the little metal plunger in before the spring for the pin retention. If you just have a spring it might be getting bent up where it slides on the pin and prevent the pin from pulling the whole way out.

Its frustrating, because when its assembled the pin extends perfectly through and has the correct looking reveal. Yes, I know for sure that the plunger is there, then the pin, then the backing plate. I might have to try a new pin I suppose.

Thanks to both of you.

Stay safe out there!

Spektek · Sep 27, 2020

Did you mill the lower yourself?

First thing does the rear take down pin slide smoothly by itself? (No upper attached?)

If you remove & reassemble the rear takedown pin & detent & reinstall it , does it fit the same?

Its odd the pin is binding On the very bottom, so im curious of a few things. Do you know if that pin level?

3paul10 · Sep 27, 2020

spoon059 said:
The pin hole is fine, but the pin itself is protruding ever so slightly into the opening. I've already staked the castle nut, so I don't really want to take it apart and try to assemble it again but it looks like I don't have much of a choice.

Its frustrating, because when its assembled the pin extends perfectly through and has the correct looking reveal. Yes, I know for sure that the plunger is there, then the pin, then the backing plate. I might have to try a new pin I suppose.

Thanks to both of you.

Stay safe out there!

.

Before you do anything, try to pin the upper to a known, in-spec, lower......it may not be a "pin" problem but a pin "hole " out of spec problem.....if I hanemt seen it I wouldn't suggest it..... let me know brother....

smokey · Sep 27, 2020

That pocket looks wak. Is it off-center? It looks like the walls are thicker on the safety side than the mag release side.

Sgt. Psycho · Sep 27, 2020

3paul10 said:
I have bought several uppers lately, all from the same vendor, and the pin holes are out of spec and dont line up with my other known correct lowers....just like 2013 shit...

Clandestine warned us a few months back that this was going to happen with AR parts.

outrider58 · Sep 28, 2020

Replace the pin.

3paul10 · Sep 28, 2020

outrider58 said:
Replace the pin.

Whatever you do, do Not follow any advice given by a clown. Clowns clown around a little too much.......

E.Shell · Sep 28, 2020

3paul10 said:
Whatever you do, do Not follow any advice given by a clown. Clowns clown around a little too much.......

"Sure, I have a spare detent. Yes, yes, that's it, come on down in here, I'll make sure you get it..."

It sounds like a defective pin, in that the end of the slot for the detent stops too soon near the end of the pin and doesn't allow the pin to retract fully.

Concur with the clown; get a new pin.

Magnumite · Sep 28, 2020

Out f curiousity, do they make take down pins in undersize (diameter) dimensions?

cotman68 · Sep 28, 2020

Change the pin out. I used a dental pick to remove the detent to avoid taking the plate and castle nut off as mine was staked also

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smokey · Sep 28, 2020

Just curious, have you measured the wall thickness on both sides yet?

outrider58 · Sep 28, 2020

smokey0118 said:
That pocket looks wak. Is it off-center? It looks like the walls are thicker on the safety side than the mag release side.

smokey0118 said:
Just curious, have you measured the wall thickness on both sides yet?

The same thing occurred to me(we saw that last year on here), but the more I looked at it, I believe it is camera angle playing tricks?
A set of calipers will answer that question for sure though...

omegared24 · Sep 28, 2020

3paul10 said:
I have bought several uppers lately, all from the same vendor, and the pin holes are out of spec and dont line up with my other known correct lowers....just like 2013 shit...

Same here. One lines up fine while the other catches. I'm going to file it down a bit so it doesn't have that lip anymore. I won't even mention the feed ramps. Same garbage on both. I just assembled an upper and gave it to a friend to test for the next few months. We'll see if he has any issues. I specifically asked him to beat it up.

Just got a few BCMs so we'll see how those work out.

MigraineMan · Sep 28, 2020

Does this thread title sound kinda naughty, or is it just me?

Shamr0ck · Sep 28, 2020

MigraineMan said:
Does this thread title sound kinda naughty, or is it just me?

Too funny.... be even worse if the title was, take down pin was rubbing my rear....

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spoon059 · Sep 29, 2020

MigraineMan said:
Does this thread title sound kinda naughty, or is it just me?

I would hope it's just you... but apparently not!

The sidewalls are equal, .21". The rear pin is 1.01", same as several other rear pins. I didn't get a chance to throw that particular upper on a different lower yet.

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Rear takedown pin is rubbing my upper

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