Over sized AR Lower Parts

[Shimitup]

I'm working on my first AR build and I was wondering if anyone knew about the availability of oversized parts, in my particular case a safety with an over sized shank. I'm mot pleased that the safety allows about 1/3 disengagement of the sear, I need one with about .015 more meat on it. My hammer hook is humongous and I intend to trim it but not until I can provide a safety that maintains near 100% lock up.
Thanks

 

[edwardware]

The AR action was designed to be assembled from parts produced in a toaster oven factory; function despite sloppy fit is a feature.

If you intend to contact fit the safety, you'll need to start with a welder. I suggest adding a pad to the trigger tail and reworking it back down.

BTW: I'm not criticizing, I have done this myself, for fun. It's not hard, it's just really unnecessary. . . like ball bearings on a dump truck clutch pedal.

So, if you intend to pursue this, I suggest you have a spare trigger and disco on hand first.

Leave the hammer alone and add a pad of weld to the underside of the trigger tail to reduce engagement. Grind it down to set engagement, then grind the top of the trigger tail to contact clearance against the safety. Now you'll need to fit the disco to just release the hammer at trigger-forward.

When you're done, you'll have a very nice trigger. . . that will double if you milk the trigger or don't firmly shoulder the rifle. You may now install the spares I mentioned earlier, and since you only touched the trigger and disco, you only ruined the trigger and disco.

Not that I would know. . . but all my ARs now wear a stock FCG with the exception of nickel-boron plated triggers for reduced grit.

 

[Shimitup]

Thank you sir. I do prefer not to weld high carbon steels however, I'm always afraid of embrittlement or outright fractures in the heat affected zones. I've considered drilling the safety and inserting a pin to be trimmed to length or sleeving the safety with a shim stock clip. At some point I'll probably drill the receiver under the trigger toe for an overtravel screw.

 

[Kp321]

Try the $.29 trigger job. Buy a 1/4-28 set screw at the hardware store and screw it into the grip screw hole. (Might have to shorten grip screw a few threads) Screw it in far enough to bear on the tail of the trigger which will reduce sear engagement and greatly improve the trigger pull. It takes some tweaking to hit the sweet spot between heavy pull and hammer follow. Might have to grind on the top of the trigger tail to ensure the safety will engage.
Be sure to thoroughly dry fire test before trying with live ammo.

 

[edwardware]

Thank you sir. I do prefer not to weld high carbon steels however, I'm always afraid of embrittlement or outright fractures in the heat affected zones.

I'm confident that you know more of welding than I, but consider:
- the stresses in the trigger tail are very low, nothing like the stresses at the sear/hook interface or pin holes. Which is why:
- every stock basic FCG I've seen in recent decades is MIM, not billet.
The weld is really a shim, not a structural weld. You could do the job with a good epoxy, but oil might loosen it given long enough.

 

[Shimitup]

I'm confident that you know more of welding than I

OOOoo, I don't know about that, I'm quite good with ac and dc stick welding but I'm likely to blow small parts to smithereens. I think what I would like to know as a base line is to find cad drawings to indicate what a milspec trigger actually is. I bought a CMMG lower kit last week at a decent price, I know they've been around a while. The sear angle is seriously positive, I know that's where much of the pull weight is coming from. It's also marking the hammer hook only on the left side so that's clearly not square. Tonight it gets pulled with a trigger scale then comes apart for complete dimensional measurements. I'll post the results.... If I remember.

 

[BBBBill]

Buy an ALG trigger group. Same folks that own Geissele. They are great basic parts with the added benefit of some expert attention to fit. https://algdefense.com/lower-parts.html $50-70 and you are good to go.

 

[Shimitup]

Thanks BBBBill, Looks like a definite step up from run of the mill budget sets. My trigger breaks at 9.5 lb. 18oz of that is the trigger spring. Sear engagement is .060. The positive rake on the sear cocks the hammer an additional .040 before it breaks. I'm sure I can clean things up, all I'm after is around 5lb and clean.

 

[BBBBill]

AR parts are a bit trickier than others to clean up safely. The Case hardening is very thin. Few can do it and have it last a long time. Sometimes you get lucky....

 

[Shimitup]

Try the $.29 trigger job. Buy a 1/4-28 set screw at the hardware store and screw it into the grip screw hole. (Might have to shorten grip screw a few threads) Screw it in far enough to bear on the tail of the trigger which will reduce sear engagement and greatly improve the trigger pull. It takes some tweaking to hit the sweet spot between heavy pull and hammer follow. Might have to grind on the top of the trigger tail to ensure the safety will engage.
Be sure to thoroughly dry fire test before trying with live ammo.

Thanks for the tip about the set screw, that trick works great. I went to the shop and looked in my set screw bin and lo and behold there was a 1/4 28 in the bottom. Once I had it set I did have to take a thread off the grip screw. I dried the threads with brake cleaner and compressed air so that the locktite 290 would wick after the adjustment was all set. I did have to level out contact on the sear and I changed angle just a hair, quite certain the case hardening is still intact as I only took off about .002 and it still felt really slick stoning it. The scale shows the break just a hair under 5 lbs. Next I'm hoping to find a 6-40 in my small setscrew bin for the overtravel adjustment. I just have to remember where I put my small setscrews.