Problem with selector on new build

AR/M4 AR Technical Discussion
1

I am working on a new build. The Lower is a S&W and it is being built using a DPMS LPK (Yes I know, I know).

Everything is fine except the the selector. It clicks into place halfway between safe and fire. I can continue to rotate it to fire with no problem but there is a very discernible point where it snags up. In addition it is pretty tight.

I tried a different spring but that didn’t help. I also inspected the selector and it seems smooth. The only thing I can figure is that the Grip is not drilled out quite enough and there is therefor to much pressure on the selector. However before I break out the drill I wanted to get others options.

By the way the grip I am using is a FAB AG-43 not the stock grip.

2

I had a selector that had the same symptoms.
I noticed a very slight casting flaw on mine.
I called the manufacture of the AR.
They sent a new selector, problem fixed.

3

I had the same issue with a DPMS parts kit. Pull the selector out and look at the groove. There will be a mold line that needs to be filed down.

4

I attempted to fix my selector with a file. I couldn’t get rid of the problem. I think the problem with mine was more of a misalignment of tooling as opposed to ridge. I might have been able to fix it but I didn’t want to mess it up so badly I couldn’t get it fixed by the manufacture.

5

Just a thought.

Before actually drilling the hole in the grip deeper, take a drill bit and twist it in the hole by hand. There could be some material left in the hole that is preventing the spring from moving freely. Actually drilling the hole deeper will probably ruin the grip unless you have some way of carefully controlling the depth.

If you want to switch out the selector, I think Armalite has them in stock along with the spring and detent.

6

I have one that does it as well, guns 100% but Id like to fix it too.

I had planned on just getting a new selector, but Ill stay tuned for details

7

Can you pull a selector out of another weapon and see if it has the same problem?

8

I had to hone my DPMS kit down a bit in several places but it’s the only one Ive ever tried so I cant say this goes for all other DPMS kits.
For your issue, I suggest you…

  1. try another selector if available
  2. inspect the selector groove and hone accordingly – as suggested in an earlier post.
  3. measure the hole on your grip, see if it’s as deep as your other ones.
    Keep us posted.
9

I did a much closer inspection of the selector and there was a cery minor inperfection in the groove. Once I can find my detail file set I will work on it.

10

#240 sandpaper did the trick on my magcatch. Finished it off with a finer grade for a smooth finish and some cold blue to refinish it.