Thanks for replying Joroji. I wonder if hammer spring is really the reason, because ShootingSight trigger work for both 16s and 17s but it also replaces the OEM hammer spring like Timney. You do bring up a good point about the self contained unit (which is indeed unique to Timney trigger) though.
The only difference between the Timney 16 (690) and 17 (691) is the hammer spring. You can swap them out at will and Timney will send you whichever one you lack. The 16 is supposed to have a ~3 lb trigger and the 17 ~3.5 lb.
Anyone have opinion on it vs the Geissele? I'm about to pull the trigger on one because I'm sick of waiting for a Geissele. F-ck me for selling the extra one I had (didn't know I was going to acquire another scar so soon at the time).
The trigger break is VERY good on mine. However what I don't like is that the reset feels a bit sluggish doing quick double-taps (like for 3-gun). If you're doing mostly target/bench type stuff, the Timney is awesome. If you're more of a run-n-gunner or for combat I'd personally go with the Geissele or Shooting Sight.
Here's the original discussion of my issue (it's not bad and probably wouldn't be noticed by most people).
When the Timney SCAR trigger was introduced, some guys experieced light primer strikes in the 7.62 guns so T offered a new model, the 691S, which incorporates the heavier tension hammer drive spring. The heavier tension drive spring increases the pull by .5lb. That's the only difference between the 690 & 691.
I've sold, shot, and installed many of the T & G triggers, and both are excellent, and both have their + & -.
Have the Timney 691S in stock @ $250 shipped if you decide to go that route.
Timney also states that the 691 also has increased hammer mass and as Sarge said .5 lb more spring tension to avoid lite primer strikes. I use Timney triggers in seven of my rifles and have never had a problem with any, some 20 yrs. old. I think they are great triggers. The one just developed for the Tavor, from my research is not so great, so I opted to wait on Art to complete his Tavor trigger :-o for mine. By the way, two more weeks right ? If I don't get it soon my finger is going to look like a bratwurst with mussels and veins. I don't get the whole battle vs bench. A bench trigger is usually less than a lb. . I want my trigger to be crisp and lite, 3 to 4 lbs. .
I have the Geissele in both my Scar 16 and 17. I emailed them a question about the trigger in my 17 feeling a bit heavier than the trigger in my 16. Within 15 minutes Bill Geissele himself responded to my email with some things to check and try out. I followed his instructions and now the trigger in my 17 feels much better. Their products are top notch and customer service doesn't get much better than that! Another very happy Geissele customer here who will continue to support them anytime I need a trigger.
I am squarely in the Geissele camp. My Super SCAR, 2xSSA-E and a SD-E have all served me well. I found what I liked and stuck with it. I plan on picking up a Sabra for my Tavor when they release it as well. I have no personal experience with Timeny triggers, so someone else will have to chime in.