COAL variance. How much is reasonable?

D

ditchdonkey

New member
EE Expired
Rating - 0%
0   0   0
Hello folks.

Just wondering, after I have my dies set to my desired COAL, how much variance from one cartridge to the next is reasonable? 2 or 3 thou difference seems understandable to me, but it can be as much as 5, even 7 thou on occasion.

I've read that some say you should seat some bullets 10 thou off the lands. So if that's how you set your dies, and then the cartridge is 5 thou longer, that's 50% closer.

Is it possible I do not have something set right? I am using RCBS dies, and everything seems snug.

Any input is appreciated. Thanks.
 
Measuring the overall length from base of the cartridge to the tip of the bullet can easily give you more than 10 thou difference in length between rounds. Bullet tips are not always uniform. You should use a comparator (home made or otherwise) that measures on the ogive. This is the part of the bullet that touches the lands and is "more" uniform. Few bullets are perfect.

Just load up for now and go shoot. :)
 
Welcome to CGN!

I agree with Warrenb, measuring OAL doesn't tell you what you want to know. A better practice is to use a bullet comparator so that you measure the cartridge length from the head of the case to the bullet's ogive. A poor man's solution is to press the bullet nose first into the muzzle of your rifle, then under firm finger pressure turn it so a line is scribed at the ogive. In this way you have an index you can refer to. Seating a flat base bullet nose down in a case then chambering it without slamming the bolt closed and carefully ejecting it will provide you with a measurement from the bolt face to the lands. Keep this dummy round for reference. If the line scribed on the ogive matches the length of your dummy round, the bullet is in contact with the lands. From that point you can increase the jump as you see fit.
 
You must log in or register to reply here.
Back
Top Bottom