ok, so when i was assembling my lower, as i was putting the hammer in, i allowed it to slam home on the piece of the receiver that separates the fire control group well from the bolt hold open slot. now the bolt hold open won't move freely and won't hold the bolt open after the last round. how do i go about opening up the slot ever so slightly so that the bolt hold open lever will work again?

Don't attempt to spread the slot. Try spraying some lube and working the lever back and forth, if that doesn't do it, remove the stop and lightly sand a tiny bit of material---LITTLE, then re-check.

roger. that's what i was planning on doing, but i figured since the guru's of the AR world frequent this site, i would pose the query here. i will work on it and post my results.

Yep, definitely try modifying the bolt catch before the lower.  The bolt catch rubbing against the hammer is not an issue. When the last round is fired, the hammer will be already cocked upon the extraction. More than likely, it's the bolt catch and its retaining pin that's the culprit. Take the roll pin out and see if the bolt catch binds in its slot using a smaller punch tool as a placeholder. If it's fine, then you may have to open up the roll pin hole in the bolt catch. With my M1S kit, I had to use a small drill bit to increase the hole diameter just enough to not bind on the roll pin.

NEVER allow the hammer to hit the front of the receiver.  When dry firing, checking function, use a piece of rubber (I have a strip of rubber cut from an old rubber boot for this) or plastic placed in front of the hammer.