Home Forums Hunting & Shooting AR and Tactical Rifles AR front pivot pin stuck detent removal

Well, I was assembling a nice lower for a lightweight 16” 6.5 Grendel and had my son fiddling around the work bench and the detent pin was pushed in the hole that holds the detent and spring, before the spring. It went in past the end of the detent (nothing sticking out to grab) and I can’t get the sucker out. Tried a rubber mallet, Super glue on end of Allen wrench, and sliding a powerful magnet down the side of the rcvd hoping to drag the pin forward to get it out. No luck moving it. Anyone have any other ideas? Can a machine shop get it out? If not I guess this brand new lower is toast. Crapola

Try tapping the front of the receiver down on a hard surface to see if it will slide forward or down. I usually have the opposite problem, I stick the spring in, the detent, and while trying to put the pin in I launch the detent pin into outer space (or at least my shop's equivalent of it)...

Cut the detent spring shorter, and reload it with another detent pin on the front end where it should be.

It’ll work just fine, but you may need to trim a couple times.

I"d have to go look. But there should be a drain hole there somewhere for water to get out of. I'd be thinking about a way to apply some air pressure to that hole as best I could. Air hose and ball inflator needle cut off or something along those lines to seal it and get the air working for you.

It doesn’t have the extra vent / water hole.

Brand new Aero M4E1

Two pin option and shorter spring option is interesting. If I can’t this bugger out that may be worth a shot

Don’t over think it - the shortened spring will work fine, and you’ll never know it’s short.

Posting for a friend… 😬

Try spraying some WD40 down the hole and tapping it on the bench. If that doesn’t work, try B12 Chemtool, it’ll dry out the oil and it might come out with it.

It’s put it in a vise block and smack it down hard to see if I could get it out.

Are you sure it’s in there ?

Some guys use wooden dowels to tap the so they stick in the end of the dowel if it’s a roll pin - but it depends what way the pin went in.

Try a blast of air, but be prepared that if it does work, it may launch the detent!

If that doesn't work, I'd do the short spring thing. All it's for is to keep the take down pin from popping all the way out.

Thx fellas. Nothing is working so I’ll be shortening the spring and adding a second detent

Didn't think to ask and don't recall seeing.
Front or back takedown pin?

Duh! Finally reread the title! 😖

Id try to get it out, just because.....but not waste too much time/energy.....as the solution is as you described.

That would keep me awake at night...for a while, anyway. There's got to be a way to get it out, but I'm not the answer guy.

It isn’t coming out. I don’t think pushing it in all the way, shortening the spring and using a second detent is gonna work, not on this action anyway. With the detent all the way in there isn’t enough room behind it for the second detent, let alone the spring that needs to go in there as well. The hole isn’t deep enough.

Crapola! New lower on the way. Great way to burn a Ben Franklin.

Toothpick with a small drop of super glue on the blunt end?

At this point you don't have much to lose.

Tried the toothpick / superglue to no avail. I have one of the long skinny magnets on order but this thing fit right so I doubt that will pull it out. I bought a $25 large magnet retrieval tool yesterday and cut the big magnet out, put painters tape in it and ran it alongside the hole. The pin didn’t budge. The different things I’ve tried have me at about $50, half the cost of the lower.

I would use the blunt end of an appropriate sized drill bit, some 5 minute epoxy, and a little oil. Oil shank of drill bit lightly, put a SMALL drop on end of drill bit and push in to butt up against the detent pin. Let dry for about 15 minutes. The epoxy won't fully harden for 12-24 hours but should stick well enough to pull out. The oil on the drill bit shank will keep it from adhering within the hole. Rotating the drill bit with a pair of pliers will more than overcome any residue glue that squeezes out along the sides of the bit. Good luck

Tried heating the housing?

Tag to see end result

Drill a small drain hole in the back end of the the channel. With a fairly tight fit and just a bit of oil it may be creating a vacuum behind it when it tries to come out by tapping it on something, etc. Then you could use air to blow it out.

Does anyone make a threaded pin that works without a detent? Wouldn't be as handy but saves you from tossing that receiver.

Try acetone flushing using a small syringe type tip while holding the lower with the hole down..........that will flush any residual oil out that is holding it, then dry it with air & try tapping it out or try the magnet again.

If that doesn't work, just use the short spring method.

MM

If all else fails try to find a screw type pin like Colt used on the SP-1’s.

Just don’t get the later type that were for large pin conversions.

I think you have the first pin stuck only part way down the raceway hole for it.

The detent spring is 1.03 inches in length, and the detent pin is .324 ~ish in length.

If the spring compresses 50%, and that’s generous - that’s at least .500 plus .324 for .824 needed to install the spring and pin.

Two pins shouldn’t be more than .648 - in length, so if the second pin isn’t able to go in the hole, the first pin isn’t fully seated at the end of it’s raceway.

The raceway should be .965-.985 in length - leaving room for a short spring between the two detent pins.

This is what I was describing before.
https://www.specializedarmament.com...ivot-pin-assembly-small-0.250-two-piece/

If that is correct it must have two detent pins in it; one put in before I bought it “new” at a gun show and the one I’m responsible for. That kinda makes sense as the spring didn’t want to compress enough for installation even with the installation tool. I was having a very hard time with it.

With what should be 1 pin in it I can’t push the pin in any further, that is with a punch and brass hammer tapping it as hard as I’m comfortable with. I bet it had a pin in it when I bought it. Will try the drill bit / epoxy option and if that don’t work the threaded take down pin may be a good option. I don’t plan to separate upper / lower often. This was planned to be a lightweight 6.5 G deer rifle with 16” Faxon Gunner profile barrel.

Thanks for all the ideas. I appreciate it!

No need to buy a whole new lower. If you absolutely just can't get it out, here's a few things you could do to salvage it.

Option 1
Seat the detent as far back as possible. It's OK to use a hammer and drive it on in. Shorten the spring, buy new detent and still use the lower.

Option 2
KNS Precision Enhanced Takedown Pin