OzFclass

the question i have is this. if i insert a projectile in a blank shell and close the bolt on my rifle to push the projectile in to touch the lands and my digital calipers read 2.794 inches. as i am not very engineering minded what length should i have to give a 10 thou jump? also is 2.788 a 6 thou jump? thanks in advance for any info.

whippy wrote:the question i have is this. if i insert a projectile in a blank shell and close the bolt on my rifle to push the projectile in to touch the lands and my digital calipers read 2.794 inches. as i am not very engineering minded what length should i have to give a 10 thou jump? also is 2.788 a 6 thou jump? thanks in advance for any info.

1 "thou" is 1/1000th of an inch. To put it another way 1mm is 40 thou, so 10 thou is a quarter of 1mm.

You are correct, if your overall length with the projectile touching the lands is 2.794", then 2.788" is 6 thou less - giving you a 6 thou jump. Therefore an overall length of 2.784 would give you your 10 thou jump.

Whippy,
2.784",2.788" will give six thousand of an inch jump. This assumes that the projectile doesn`t move in the removal from the chamber. I use a Stoney Point Bullet Comparitor to measure seating depth.
Mike.

thanks for the info. it helps me heaps.

Also remember that if you are measuring off the bullet tip your figure will vary wildly due to the differences in overall length of the projectiles so don't go chasing the same overall length for every loaded round- measuring off the bullet ogive should be more accurate.

Michael