So, just to get the obvious out of the way, but is the bolt lubed? I would wet the bolt lugs a bit with lubrication if it's a new bolt. New bolts can be tight if it's a new bolt with a new upper receiver. Usually takes about a 100 rounds through it to smooth out the rough edges around the locking lugs on the bolt and chamber. I always over lube a bit if it's brand spankin new. Try lubing it it up and rack the bolt back and forth a few times. Don't let it slam at first and just ride the charging handle in and out. After a few times it might start to loosen up a bit. Again, make sure the lugs are wet with lube.
If your bolt is lubed up and absolutely refuses to lock in all the way and it's extremely tight, then something may be out of spec. Might try a spare bolt if you have one. If the spare works, then your bolt may be out of spec, otherwise if the other bolt has the same issue, then your barrel extension may be out of spec or upper receiver may be wrong.
My new loki upper was a little gritty and tight with the Spikes BCG I bought for it. Initially squirted some synthetic motor oil, but was still gritty with that, so I wiped it all down and used some Slip2000 EWL gun lube and it was much slicker with that stuff. Ran about a 100 rounds and now it's pretty smooth.
