Originally Posted by trueblue
What are the advantages of a cone faced bolt.I am not a machinist, but it would seem to be harder to cut a 65 degree recess ( for example) in the breech of the barrel than to just take a .705 counter bore to cut the recess for the bolt face.
A cone breech facilitates chambering as it's a uniform feature that acts as a funnel for the cartridge as it enters.
Machining the feature is pretty simple. Just set the compound on the carriage to the angle and begin making passes until it's at the right depth to ensure the bolt/breech clearance is right.
Some do lots of kinky math to determine this, being a lazy person I found a way that involves less work. I got some lead wire and I stick a piece to the bolt on the forward lug surface. As I rotate the bolt into battery the wire is smooshed between the lug and the breech.
Measure the wire with a pair of calipers and I know without a doubt what my clearance is.