I just got finished at the range.
Couple of things to note:
It takes a lot of effort to get it into battery. Not always, but sometimes.
It takes a lot of effort to get it out of battery. Nearly always.
If it doesn't go fully into battery, it's a BITCH to get out.
This particular Timney trigger is worse than any milspec I've ever used. It's supposed to be set at 3lb, but it feels much more like 8 or 9! I'm going to blame that & the scope for the fact that it shoots like crap. 3" was the best i averaged, but since I couldn't get a full 10 shots together in a string, it's hard to say.
I'm going to try a different bolt head. I've had issues with nickel boron bolts in the past.
The crappy groups could be trigger induced for sure, like you say. Lightweight rifles probably need light triggers to reach their potential. On my very first AR, I went through a pretty big learning curve figuring out how to shoot the damn thing better than 3 MOA. Someone more knowledgeable told me that's all I could get from a cheap AR and would need to spend north of a grand to get one that shot well.
Not being very good at giving up, I lightened the trigger, worked on handloads, and maybe most importantly experimented with bench techniques. Within a week or two I had a 55 TTSX load that shot sub-MOA as well as my bolt rifles. So much for needing a $1K AR; they truly are amazing rifles for what they are.
As far as bench technique, the biggest aha moment was simply changing my front bag. I use a fairly long bag (about 10") with my bolt rifles. On a whim I tried an old short bag I never use. My groups immediately shrunk about in half. I'm not sure why, but for me, the AR wanted something different than my bolt rifles.
Also, placing a soft towel folded on the front rest (and rear rest as well) seems to help with light rifles in general. I think they're more prone to bounce on a hard bag than are heavier rifles. Shooting off of a pack does a good job of mimicking the soft front rest. Haven't tried it yet, but the towel in the long bag may have worked as well. Once I figured out something that worked I haven't messed with it too much.
Keep experimenting with ideas and techniques. The rifle can do it, just have to figure out what it wants in order to do it. For me, shooting ARs well was kind of like re-learning to shoot. Not saying that you're doing this, but after I quit insisting on treating them the same as my bolt rifles, things started coming together.