Gas block and front site I installed to barrel first, make sure you put the half moon piece in receiver. I thought about building a jig but tried without, using wood on the bottom against receiver, and wood on top of muzzle thread protector. Barrel left out in cold, and receiver just above wood stove to warm. I used a film of grease in receiver, my 20 ton press pushed down barrel very easy, smooth no binding. When halfway installed I pulled off press and checked indexing on barrel. turned from front site post to index. Back to press and slowly finished install looking thru barrel pin hole until it lined up perfect. I had a slightly undersized pin punch that just went thru, so I knew when I was close. Tapped in pin, checked headspace all good. My parts were a complete used kit, so if you have a new barrel then you may have to ream for setting the headspace, can only increase the head space can not decrease it unless you try other bolts. The tolerance of barrel pin do not really give you any adjustments on indexing or head spacing. Hope that helps. There are you tube videos using redi-rods, nuts, and small steel flat stock installing an AK barrel, probably could be done similarly.