An imperfection with my first AR build.

[teddy12b]

The rear takedown pin is not being secured in the closed position. When I exntend the pin out (for cleaning or upper removal) the little dent pin locks in the rear takedown pin in the open position. I've taken it apart on several times trying to figure out what's happening and why the rear takedown pin isn't locking and securing in the closed position. While I've taken the rifle to the range and fired just over 500 rounds through it I've never had a problem with the pin working itself loose.

The rear takedown pin itself shows the little countersink at the end of the groove for the dent to fit in. I've manually fit the dent into that little divet enough times to know that it will fit in there freely.

The only thing I can think of is that the takedown pinhead is just a few thousandths too thick and if I file off material from the bottom of the pin head where it touches the lower, maybe it'll lock in there.

The rifle in question is my first AR build that was a Del-Ton dissipator kit which I bought from Midway. I bought an actual Del-Ton lower from Cheaperthandirt.com so the whole rifle matches as far as manufacturer goes. I'm not unhappy with the rifle and in the big picture of things, this is a very minor issue that I could see people overlooking, but it just drives me nutts to know it's at 99.99% instead of 100%.

Anyone have any thoughts or recommendations?

 

[Txlur]

Install a new pin. That's what i'd try. Something sounds out of spec.

 

[sgreen3]

I would definitely get a new take down pin, Maybe the one you have was machined incorrectly

 

[Brando]

Are you using an accurizing wedge?

 

[Litlratt]

Increase the length of "the little countersink at the end of the groove for the dent to fit in".

 

[teddy12b]

I get that something is out of spec, but I keep looking for that rough edge to touch up because this thing is only missing by a couple thousands if that.

I'm not using an accuwedge.

 

[shibumiseeker]

I get that something is out of spec, but I keep looking for that rough edge to touch up because this thing is only missing by a couple thousands if that.

I'm not using an accuwedge.

It could be the pin out of spec on either side (under the rim or the length of the groove), or it could be the lower is a few thousandths thicker, or some combination of all of them. Simplest is to try a new pin, they are not expensive.

 

[teddy12b]

Yeah, the more I think about it, I'm just going to have to buy a new one and try it out.

 

[sloughfoot]

Bring the rifle to the 100 yard offhand league match this Sunday. Be there by 1145. Several guys can take a look at it. Some might even have pins in their spare parts box.

I hope to see you there. If you want, I will have another rifle. But I hope you shoot what you brung. Your choice. 5 bucks, just for fun, no pressure except for what you put on yourself.

Regards,

www.fwrr.us for map to the range.

Dean

 

[jblomenberg16]

I had a safety selector that had a similar issue. Detent wouldn't lock it in "fire." Replaced the selector and it was fine.

 

[teddy12b]

Well I picked up a new pin last night at Ranger Supply. I'm pretty sure they're the only store in town that would have one on the shelf and I wasn't disappointed. When I got home and installed it, I had the same result. It's not that big of a deal, it's just that I'm always going to know that something isn't quite right and that's going to bug me.

I'd love to meet you out at the range on sunday, but I have Christmas with the in-laws.

 

[shibumiseeker]

Well I picked up a new pin last night at Ranger Supply. I'm pretty sure they're the only store in town that would have one on the shelf and I wasn't disappointed. When I got home and installed it, I had the same result. It's not that big of a deal, it's just that I'm always going to know that something isn't quite right and that's going to bug me.

I'd love to meet you out at the range on sunday, but I have Christmas with the in-laws.

Sounds like the receiver is out of spec then. I'd modify the pin under the rim, call it good, then try to forget about it. Hard I know, it'd bug me the same way.

 

[rvb]

Increase the length of "the little countersink at the end of the groove for the dent to fit in".

yup.

-rvb

 

[teddy12b]

I started to file off some of the material underneath the pin, but it's at such a sharp angle and so small that it's hard to get at and I didn't have the time to do it right last night. I'm just going to have to spend some quality time with the pin and a good file.

 

[Litlratt]

A Dremel with the proper bit and it should be relatively easy.

 

[rvb]

going at the underside of the pin head is really making a simple thing hard. littlerat is spot on. enlarging the catch in the pin channel the detent catches on would be so much easier. dremel + small ball cutter = done. you could even go at it w/ a drill bit slightly larger than the existing hole at the end of the channel. it would be a 15 minute fix (14 of those rummaging around in the garage looking for the correct cutter or drill bit... haha).

don't make the pin sit deaper, make the detent catch larger.

-rvb

 

[teddy12b]

dremel + small ball cutter = done

This is exactly what I did. I was lucky and had a dremel attachment kit with a little ball cutter that just happened to be perfectly sized for the job. I just had to barely touch it up and now the dent actually engages like it's supposed to. I couldn't be happier!

Thanks for all the help guys!

 

[rvb]

I couldn't be happier!

-rvb