Hello

I'm trying a bit of gunsmithing on my AR15. I want to add an overtravel stop to the trigger.
I found the tap and drill. Borrowed a drill press, set everything up. I thought I was good to go.
I ran into one small problem. The trigger is surface hardened. I didn't think this would be too much of a problem. But it was.

My starter punch didn't make a dent. That was my first clue this wasn't going to go well.
I had two drill bits. One regular drill bit and one fancy coated drill bit. Neither bit would go through the hardening.
I played with the speed and kept the pressure light. Even found some cutting oil, or something like it(not my shop). No luck.
One bit broke under light pressure. The other just wouldn't make a dent.
BTW the drill is a #43 to go with a 4-40 tap.

What is the proper procedure to drill and tap a hole in this trigger? Here a pic of a AR trigger.
If you aren't familiar with an AR trigger the other side isn't solid. I only have to go through .080" of material.
The badly drawn arrow is about where I want to drill and tap.
I'm not going to be insulted if someone tells me to go to the machine shop across the street from me.
I thought of that, but they keep bankers hours and were closed.



Thanks in Advance

ZM

Brownells sells single flute carbide bits that may be able to break the hardened surface- if it is only the surface that is hardened.

&related:

http://forums.accuratereloadin...9411043/m/7891073521

After the sear breaks there is some distance until the end of the pull. When the trigger is released there is some take up.
I want to eliminate that take up.
If you look at a JP Enterprises trigger for example, it has stops at both ends of the trigger.
I'm tackling the stop at the rear first. Then I'll shoot it for awhile and try to install a stop in the front.
And it won't be adjustable. Once I get it fitted. It will be there forever.


Overtravel stop might not be the proper term, but you get my meaning.

You can buy these carbide drill bit assortments in hobby catalogs:


These are re-sharpened drill bits originally used for printed circuit boards. If you get some get the big assortment (or 2 boxes of them) as they break if you look at them crosseyed but set up in a drill press with speed on overdrive they do a good job. A #43 bit is like .089 and I'm sure you'd have something in a box.

My next suggestion would be to buy a pointed dremel grinding stone and use that to drill through the surface, then follow with your bit. Don't plan on being able to use the grinding point for anything else when you're done though.

Hope that helps!

Drilling is the easy part.

The trigger is metal/plastic injection molded then heat treated to remove the plastic.
It is getting super common and a friend of mine in another mold shop accross town has been involved in many molds built for the AR line of rifles and the .45 1911 pistol parts also. It is through-hard and you won't be able to tap it.

I will ask him Monday to be shure.

"Standard procedure" is to anneal the stock, machine the fitting, harden the stock.

Case hardening is a complex procedure requiring temp control and some other stuff. I stopped reading at the "temp control" stage.

Above -- drill the hole all the way through the trigger, tap/thread all the way through. Run the set screw in from the front. Hex key drive.

I'm pretty sure there are after-market triggers for AR which provide precise pull-weight and travel adjustments.

Timney, Midway off the top of my head.

http://timneytriggers.com/

www.gunblast.com/Timney.htm

Zeke,

If I am understanding you correctly, you can also install a set screw in the lower receiver frame below the trigger tang.

You can remove the trigger assy and drill down through the aluminum and come out in back of the trigger. Then tap that hole for any kind of set screw you desire. It can be adjusted by just swinging the trigger guard out.

I did this on my old "war horse", and it worked for several thousand rounds. It finally started doubling and I had to give it a little more engagement.

I did it because I didn't have the money at the time, but after putting a Timney in the last AR I built, I just won't do it again.

Jim

quote:

Originally posted by Gundog 64:
Zeke,
Now Im cookin with flame. Thanks for the clarification.

John

You're fine. I ask questions here all the time. We all have to learn somewhere.
Black rifles are one of the few areas of this hobby/addiction that I sometimes know what I'm talking about.

I found out the entire piece is heat treated to keep it from wearing out from engaging the sear. Which is why I couldn't drill it. One of the people that responed said it would have to be annealed. He was right. I don't have the ability to do that...yet....

I'm farming it out to a gunsmith. He's going to do the work for me for a fair price and allow me to take meticulous notes.

I don't think I can put a stop on the front if it has to be annealed. That area is too close to the front engagement surface.

I'll take a look at one of my spare lowers and see if I can put the stop in the lower.

Damned black rifles. They are the firearms equivalent of crack.

quote:

Originally posted by pdhntr1:
Zeke,

If I am understanding you correctly, you can also install a set screw in the lower receiver frame below the trigger tang.

You can remove the trigger assy and drill down through the aluminum and come out in back of the trigger. Then tap that hole for any kind of set screw you desire. It can be adjusted by just swinging the trigger guard out.

I did this on my old "war horse", and it worked for several thousand rounds. It finally started doubling and I had to give it a little more engagement.

I did it because I didn't have the money at the time, but after putting in a Timney in the last AR I built, I just won't do it again.

Jim

I saw that on my spare lower today. That is plan "B".

I'm going to try that or something similar on one of my other AR's.

Superior has an adjustment built into the screw that bolts the grip to the lower. I'm going to try making a stop that way too.
By the time I figured that method out though, I had already got in touch with my gunsmith.

I'll pull that screw out, get a rough measurement and give that a try.

Thanks for jogging my memory.

I already have a way to smooth out a stock trigger without messing with the springs. This is the next step.

ZM

A nice hex would look much better, but this thing is retired.

On the Jard adjustable trigger, the set screw at the front of the trigger is the over-travel adjustment. The set screw at the rear is the safety adjustment screw. The take-up, or sear engagement adjustment, is a set screw that comes up through the pistol grip bolt hole. Adjusting sear engagement and/or overtravel usually means that you have to adjust or modify the disconnect lever or the hammer will just follow the bolt down and you end up with a loaded but uncocked rifle.

Trying to do all this on an issue trigger quickly convinces most folks to install an aftermarket trigger.

UPDATE....Solved

Plan A, the drilling didn't work. My gunsmith tried heating it up three times and the trigger was still too hard.

We decided on a Plan B after I noticed he had a arc welder. He put a small bead of weld on the rear of the trigger.

That accomplishes the same thing as a D&T. I can fit, grind and fit until the trigger works the way I want it.

quote:

Originally posted by M Pursell:


Trying to do all this on an issue trigger quickly convinces most folks to install an aftermarket trigger.

I know.

I'm bored. I'm a confirmed tinkerer. The tinkering get worse when I have lots of spare parts to play with.
I could have shipped the trigger to Bill Springfield. But that would be too easy and make too much sense.
With football season all but over, I have to do something on the weekends. This stuff keeps me out of trouble.

Understood. The best way to figure something out is to try it. I was just giving you a heads up based on my experience.

Although I've installed a lot of aftermarket AR triggers, I'm too cheap to buy one for my own gun. Something about cobblers' children leaving bare footprints in the snow comes to mind.