I installed a barrel in a new milled receiver aligning the 7mm pin to the old hole in the barrel and the bolt seems to be a little loose, I have fired the gun about 20 rounds and it functions fine.  My question is when I compare the bolt fit to trunions on other kits it is not as tight.  Am I lucky that this thing has not exploded in my face?  The gun seemed pretty accurate and ejected cases showed no signs of stress. This is the first Ak that I have ever fired and the way it fires now seems to be more accurate than my sks.  One more question before I build my next kit- I read on another web site that the bolt carier must be grinded where the auto sear would be tripped or engaged, I did this on my first build but my next build is of all matching serial numbers and if possible i would like to keep this kit as close to original as possible.  The kit did not come with the sear parts and obviously my receiver is only semi auto would this be ok or should I also grind the bolt carrier just to be safe.  Any help would be greatly appreciated.

you are lucky..  it didn't rupture a case..
you head space a press fit and pin milled receiver just like you do a stamped receiver gun..
get a set of headspece gages and use them.. I'm not going to post the details on how to head space as there are lots of posts on that topic already..

the only milled receiver guns that headspace differently are the ones with screw in barrels

yea

you need to headspace not cause its gonna blowup (not saying it wont just saying it prolly wont)
but it will ruin the rifle if you dont and it wrong


as far as the carrier dont worrie about it you can actually install the f/a fcg if you have us parts elsewhere