Colt milspec is fine.

I have been running  JP Match triggers on my M16 (and my other ARs) for, oh, the last ten years. I love it, and it costs a quarter to a third of what a Gisselle or Knights does. Total trigger movement from untouched to fully depressed is 3/16"; let-off is clean and crisp, like the proverbial glass rod breaking; and in a decade of use (and way more than 10k rounds down the tube), it has not lost adjustment. I put it in, adjust it, and it has run forever.

FWIW. YMMV. HTH.

Correct. The JP is single-stage in both semi and FA; the KNS and Geissele are double-stage in semi, single-stage in FA.

FWIW, I shoot my M16 in FA almost all the time –– if I want a single, I have the selector in FA and just pull one round through trigger control. (My standard comment is: "You mean my M16 has a 'semi" setting? Why bother?)

On the rare occasion when I DO switch the selector to semi, it doesn't bother me that it is a crisp, precise single-stage vs. a double-stage, because in my experience a double-stage trigger is never as precise as a single-stage. When I need to shoot semi it is for accuracy, and unless you are running a military drill that requires DS, single-stage will always be more accurate.

We are also talking a $100 SS trigger vs. a $300-$400 DS trigger. So I would rather spend hundreds less for a trigger that in my use is more accurate, vs. hundreds more on a trigger that may meet the Geneva Convention but has less practical application.

Again, YMMV.

I don't do much precision shooting today, but I did seriously for several decades. At the time, when shooting out to 1,000 yards, I preferred set triggers with pull weights in the 3 to 6-ounce range. I spend my entire life shooting single-stage (including "set") triggers, so that is what I am used to.

For so many reasons I won't bother to list them here, I would not want a 3- to 6-ounce trigger on a full-auto firearm.

I have the JP trigger on my M16 set to 3.4 pounds. At that weight, it works fine for me for both precision semi and for FA use.

AFAIK, all full-auto fire-control groups are single-stage on FA. That includes the Knight's I have used, and AFAIK it includes the Geisselle. The KNS and Geisselle are 2-stage semi, single-stage FA. The JP is single-stage for both.

I find it useful and comforting to have the same design –– single-stage –– on both semi and FA in the same firearm. Maybe some folks don't mind shooting one gun where when the selector is set to semi it is two-stage and when it is set to FA it is single-stage. But that is not me. I prefer having the exact-same trigger design, weight and pull regardless of where the selector is set.

Whatever works for you. Obviously, YMMV.

The JP trigger uses your existing milspec FA hammer, selector and disconnector. All the ones I've did required no filing, but the JP has two set screws which you adjust for pull and overtravel. It comes with a CD-ROM showing how to adjust those to your needs. Once you adjust them, you loktite down the two set screws and you are done.

Each to his own. I like to tune my gear –– eventually I'd just re-adjust a Gisselle anyway, so there's no point in me paying the manufacturer an extra $200 to "pre-adjust" it.

But you are right, Gisselles are excellent triggers.

JP supplies a tube of lube for initial assembly. After that, I just use whatever lubricant I normally use.

FWIW ... the JP EZ trigger is for semi applications only –– AFAIK, they do not make a FA FCG.

JP's original trigger, which they still sell, works for either semi or FA, though you must supply your own FA disconnector, selector and hammer. In all of the installations I've done, I have used the JP trigger and springs together with new Colt full-auto hammer, disconnector and selector. The Colt factory parts dropped right in and worked with the JP trigger with perfect function and zero fitting. The only "work" was to adjust the two set screws for engagement and overtravel.

These were all Colt factory full-auto receivers. I can't say the same would occur if you used non-Colt internals, or installed it in a conversion RR –– specs might be off enough, or tolerances stacked, that you would need to fit the disconnector or selector.