i am putting together a rock river arms lower with a parts kit i got from Model 1 sales.  when i hold the trigger back after releasing the hammer, the hammer catch will not engage the hook on the disconnector without releasing the trigger slightly.  the disconnector will not recess into the channel on the trigger enough.  one thought i have is to file a new face on the  disconnector making it shorter so the hammer will engage.  any suggestions are greatly appreciated....

also, how can i lighten the trigger pull ?  where do i need to file and what should i use to file with ?

I would not file on any of the parts, they should work correctly or there is a problem with them. Call model 1 and arrange for replacements. If you want a better trigger pull try Rock River Arms national match 2 stage trigger group www.rockriverarms.com. It is possible that the hammer and trigger pin holes in the receiver are not located correctly this is less likely but possible. Good luck.

The first AR I built was from a Model 1 kit.  I had trouble with the trigger/disconnector/hammer fit.  The disconnector would not "disconnect" without breaking the weapon down and applying slight pressure to the hammer.  I called Model 1 and they sent me a new set of parts.  Cured the problem.  The AR I am building now has a DPMS receiver and internals.  The fit is great.

As far as reducing trigger pull and smoothing it up, check out this thread, simple and it worked well.

http://www.ar15.com/forums/topic.html?b=1&f=74&t=149423&w=myTopicPop

There are a lot of crappy parts out there. I had the same problem. I just filed the top hook on the disconnector until everything worked properly. Don't overdo it! You can make sure you haven't over done it by keeping your finger back on the trigger and switching to "safe", the hammer should NOT fall.