Hey Delta,
Welcome to my world this weekend, trying to get bolt heads to do the right thing/s, they either jam as you wind them in (very slightly different thread), under or over rotate at the end of all the turns instead of being upright, wind in in pulses as thought the bolt is out of round but other bolt heads don't do this, etc etc.

I have a 1966 2a that does allow the early bolt heads with the slot to thread in no problems at all, but gets randomly persnickety on no1mk3 bolt heads without that slot.

Re threads; enfield threads are in house designs, not publicly used ones. In the real world, 50 -100 years later, you won't find them, ever. What threads are on 2a's I don't know but they seem mostly like no1mk3's.

ps, if you booga the bolt, go over to springfield sporters, they have them new and unserialed for less than $15, ez answer.