I'm a bit of a trigger snob and have used a lot in AR's. I have four Geissele triggers now, the SD3Gun, Hi-Speed 2 stage, SSA-E and the SSA. I also have an RRA 2 stage (11-12 years old?) and a quality plain jane single stage that I polished myself.
The RRA needs a bit of polish, but NOT MUCH, just enough to make it have two crisp stages. Those KNS pins work good with this trigger. Despite naysayers, I like it a lot. It lacks the attention to detail, the finesse of the Geissele trigger, but other than that it still has a good feel to it. Some folks like to change the pin that holds the disconnector with a similar size drill rod the size the width of the receiver or else fix it another way. They have been prone to coming out on some people, though I never had a problem and I've used this trigger the most of any of mine, and I actually had one in a .308 DPMS 11-12 years ago.
A properly stoned and polished quality AR trigger (DPMS is okay, LMT too; Oly very bad) gives about 4-4.5 with a factory spring. Little lower with a yellow JP spring. Good clean single stage break either way. Some people are more comfortable modifying the angles and removing more material and such, and can make these triggers sing, but I only stone and polish them. To be safe, if I need it lighter, I get a better trigger.
Geissele makes a trigger for every occasion, all those triggers actually are quite different, and they are basically it for the AR trigger. I can't believe how nice they are, all of them, they need absolutely no modification whatsoever right out of the box save the Hi-Speed. True, quality drop in with a good milspec lower. I was fortunate enough to try many of the quality triggers out there at Rainier Arms in cut lowers they have with rubber bumpers installed for testing. Wilson was very nice, another contender, but for my money Geissele was it. I thought their 3G trigger was much nicer, works just like a single stage trigger, crisp with no hint of release; it is semi auto but VERY fast and similar to the auto setting on the SSF. Not for everyone, it is the proverbial hair trigger, but a unique trigger and worth mentioning nonetheless as there isn't anything quite like it. It shows their innovation that they can make one like this, yet safe.
I must admit, though expensive, those Wilson single stage triggers are top notch items. If you want a killer single stage trigger that will last, that would likely be the one I think.
The SSA is the semi version of the SSF, it is a nice, heavier 2 stage trigger. The SSA-E, they claim, is similar to the Hi-Speed but non-adjustable making it more reliable. I agree, it is a very nice trigger and the one closest to the DMR setting I use on my Hi-Speed. The Hi-Speed is, however, fully adjustable for takeup and over-travel, has a lightened hammer to reduce lock time, along with three different spring sets, two similar overall weights with differing staging weights, and one match spring set, very light.
All in all, I think the Hi-Speed is my favorite, but for a rifle where I'd be worried about small set screws coming loose despite blue Loctite, the SSA-E can't be beat, nor can the SD-E if you prefer the flat bow (I like it, but only on the 3G IMO).
Personally, I think the SSA-E is the best bang for the buck in a fine 2 stage trigger unless you want the adjustability and reduced lock time of the Hi-Speed.
