ar trigger install

[sbo80]

second post of the night, working on a rebuild and have another issue. 80% forged aluminum lower, cut with 80%arms easy jig. I got myself a Hiperfire 24C trigger for christmas, so I'm trying to replace the mil-spec one I had in there from an anderson lower kit. The mil-spec fit fine, but the Hiperfire does not. The problem is the hammer. Underneath the pin hole is that little slot with the wire in it in the hammer (what is that even for?). On the Hiperfire, that little wire sticks out ever so slightly. So when I get the hammer in, and the pin through, the hammer won't cock back because the wire is catching on the front of the trigger pocket. There's just no clearance. I'd take a picture but it's so small it's difficult to see. I don't think it's the pin hole alignment, they are spaced exactly right for KNS anti-rotation pin bars. Can I file that little wire down flush? It's the tiniest bit sticking out. I think that would solve it, but don't want to hack into a 200 dollar part without being sure.

[SkyHawk]

Or take a little off the front of the pocket. I have seen several 80 lowers that did not have quite the right front radius or length and drop in triggers were not so drop in as a result. The fix is to just mill the pocket a bit more at the front.

But if you are sure that bit of wire is the problem and also sure that bit of wire is not important, then it sounds like a quicker fix is to grind that bit of wire away.

[Junkie]

"Can I file that little wire down flush?"

I would be very surprised if you physically could. Wire tends to be very hard, filing won't be easy.

[bauern]

That wire appears to be the one inside the hammer that snaps into the center of the pin to hold the pin in place. Filing/grinding flush with the bottom of hammer shouldn't cause any concerns. With KNS pins, you could even remove it without worry.

[sbo80]

holiday kept me off the workbench for a bit. so the wire was very hard, I have a small hand file, no good, or too slow to notice progress. Fine diamond tip dremel did the trick, got the little tip of that wire down flush without touching the hammer itself. I didn't measure, but it seriously was like .001 inch or less, just enough to catch with a fingernail (and dig into the lower). Install is fine, and it moves freely. But now, with the rifle assembled, the bcg gets caught up on the hammer when I try to charge. Hammer just doesn't lay down enough and the carrier gets fully stuck at about half stroke. Through elimination, I ruled out the bcg (tried a different one) and the buffer (pulled the whole thing off) as the problem. I put the milspec trigger back in and it all works fine. Ugh. I really wanted to like this trigger. WTF. Tomorrow I'll try to put the trigger in a different lower and see what happens.

[Cheep]

That hammer needs some CLEARANCE. Remove some material at the front of that pocket and see if it has enough room below the hammer.

[wpage]

Your pin hole may be up too far...

[sbo80]

I spent all day playing musical triggers with all my lowers. Parts everywhere. I'm pretty sure now that it's definitely the lower. The Hiperfire trigger works fine in a factory billet lower, a factory polymer lower, and another 80% that I cut with the same jig. While I get a milspec trigger to work fine, I also have the same problem with a POF drop-in trigger, the bcg gets stuck when charging. Though I didn't want to have to, my next step is to try SkyHawk's advise, and see about milling back the front of the pocket some more. I didn't want to strip down the whole lower and get it back into the jig, but I will now that I've ruled out other issues.

[kcstott]

Why don't you recut your lower to spec like it should and you won't have that problem.

[smoothy8500]

Why don't you recut you lower to spec like it should and you won't have that problem.

But where O' where would he find prints or reference materials with those specs????

[kcstott]

But where O' where would he find prints or reference materials with those specs????

[sbo80]

Fair points, but since I don't have a proper mill, and only have single cheap plastic caliper, neither of those things are relevant. That's why I got the easy jig, to use the router technique, in spite of its limitations. I didn't measure anything, that's what the jig is for. The other lower I cut came out correct. That end of the pocket was away from me in the jig, so I am assuming I didn't get the endmill shank quite all the way against it. So we're only talking a very tiny amount of that wall. Gotta start somewhere, and this has been immensely enjoyable really learning about the workings my firearms.

[ar15barrels]

That's why I got the easy jig, to use the router technique, in spite of its limitations.
I didn't measure anything, that's what the jig is for.

So put the lower back in the jig and finish cutting the front of the pocket.
The jig is likely so sloppy in how it locates the lower receiver that you can choose where to put the lower within the jig.
Moving the lower towards the rear of the jig will let you cut further into the front of the pocket, which is where toy need to be cutting to solve your problem.

[sbo80]

the 80% arms jig centers by a bolt through the pivot pin hole and takedown pin hole, so there isn't any moving front/back unfortunately. Now that I've had an issue, I'm fairly sure this was a case of being too soft pushing against the front of the pocket template. It is close enough that a milspec trigger didn't have an issue, but others do. I found, generally, I was very cautious putting any side load against endmill to keep it from chattering, which did give me smooth cut walls. I finished the second lower much faster once I got more comfortable how much I could press and how deep I could cut on a pass, I've never done any metal work before. I didn't go back to the first lower, since it didn't seem to have anything wrong with it. I do appreciate everyone's feedback.

[ar15barrels]

the 80% arms jig centers by a bolt through the pivot pin hole and takedown pin hole, so there isn't any moving front/back unfortunately.

Yes there is.
A 1/4-20 bolt is nowhere near the same size as the holes in the receiver.
There is a good 0.008" to 0.010" of clearance there.
Take up ALL the slop by holding the receiver towards the rear of the jig while tightening the bolts.