Re: Polishing AR sear and trigger creep?
I'm a bit of a barrel and trigger snob, especially with AR's since those two components affect the end resulting rifle more than anything else, though I prefer the term "connoisseur" instead. Anyway, I've done the set screw tricks on other rifles, even put one in an FAL until I installed a Jard rendering it useless. Think about that before drilling and tapping a hole in your lower.
You want a single stage pull between 3.5 and 4lbs? Crisp with little to no creep and overtravel? Try the Geissele 3gun trigger. I have one, the SD version that has the flat bow that works really well for me, and it is one of my favorite triggers. It is a 2 stage trigger, but it feels more like a short one stage trigger and it does nearly break like a glass rod.
I tried the Wilson 3gun trigger and it is really nice too. My wife, she tried 'em and like the Wilson too. It costs more and feels a little different, but it is still a very fine trigger. It also is self contained, drop in unit.
I also have an RRA 2 stage trigger. It needs a couple of things to make it reliable and smooth. 1st thing is to replace that short pin (in the disconnector?) with a cut off drill bit that is long enough to span the lower. Sometimes those factory pins give out and that can be bad. Easy fix though. Second is to polish the engagement surfaces. Just a cotton drum in a dremel does it, perhaps with a little fine polishing compound. Mine is now a smooth, distinct 2 stage trigger somewhere between 3.5 or 4lbs if I recall right.
That one and most other two stage triggers will have that light first stage and then a stiffer second stage. Fine for precise shooting, taking time on a shot. But for faster shooting, a short and crisp single stage is usually better. Geissele claims that their 3gun trigger is capable of firing 12 aimed shots in 1.2 seconds. Pretty amazing, I haven't done it yet but it is a very fast trigger due to the short pull and lack of pre and over travel.
I got to try a whole bunch of triggers before I bought one. Geissele makes a LOT of triggers, and believe it or not, they are significantly different between them. They try real hard on their site to describe them, almost like a wine, but you really need to feel them I think. At Rainier Arms, which is local for me, they have a bunch of different triggers in test rigs to try. So that is how I came to the 3gun for my SOPMOD copy M4. I wanted a fast, crisp and short trigger that was both safe and reliable. It has an EoTech on it, so no real need for a fine 2 stage, although it does work well for long shots too. I was thinking of polishing a well made standard AR single stage trigger pack, but after I tried the 3gun, I was sold instantly. It is expensive, but it sounds like what you are looking for. Look for them to go on sale, follow a few different sites or search Google shopping for it.
There are some tricks and what not to take out the pre travel and over travel, but in the end I still think you are better off with a different trigger. Polishing engagement (worn) surfaces will make it smoother, but it won't do anything about the travel. Here a cotton drum in a variable speed dremel is nice, as is a little lite polishing paste or bore paste. Doing much more than that can make it dangerous, particularly if you don't know what you are doing. If you want an accurate and crisp, short trigger with little to no p/o travel that is great for action and works well for long shots, that Geissele 3gun is it (for me anyway) hard to beat. MUCH better than any traditional single stage AR trigger I've ever felt. They make a trigger for every application you can think of for an AR, and a couple "Jokers" too, or jacks of all trade.
Now for my longer range, more accurate Grendel rifle, it'll be getting upgraded with the Geissele Hi-Speed trigger. Not sure of the lock times, but it LOOKS faster compared to all the other triggers I tested next to it. REAL fast. It currently has that RRA in it, but that'll go in the .300BLK build where it should "fit in" a little better.
But if you match your build or rifle's purpose to the description of a particular Geissle trigger, it is hard to go wrong. And if you ask me, there is no better single stage AR trigger than the Geissele 2 stage 3gun trigger! There are a lot of other good trigger makers out there (Wilson instantly comes to mind now) but I've just been blown away with Geissele as of late.
Note that any of the adjustable triggers are bound to be less reliable under stress than will be a non adjustable one, but if you do get adjustable make sure it uses a minimum of set screws to accomplish the job. Saying reliability is an issue with this rifle... If not, then have at it.
Good luck!