Originally Posted by drenge
I neck sized with a Lee collet die then seated with a RCBS competition seater. The ammunition is fully loaded when I measure the case neck.
Then like Mike says the take the .308" and subtract the amount of bullet grip you want
.308"-.003"=.305" or .308"-.002"=.306" or one of each and see which works best.
But like the others I prefer the Lee Collet Neck Sizer and Redding Body Die combination to the bushing dies. I use the bushing die in the 338RUM caliber and it works well but it just costs a lot more to do almost the same thing. The only difference or advantage of the bushing dies is that you can more easily get different bushings and vary bullet grip. However, for $5.00 Lee will make you a mandrel any size you want.
The CaseMaster is not the best way to measure neck thickness IMO. Like you said the case will tilt unless you are careful and if you measure on different places on the sliding sleeve it will vary so I mark mine
even then it only measures to a certain depth in from the case mouth. A much better tool and one that will be indispensable if you are neck turning is a ball micrometer on a stand
you can measure all over the neck and it is much more accurate
IME the stand is very very useful for working with a ball micrometer unless you were born with 3 hands.
In my limited experience, what helped most with SD & ES was the Lee Factory Crimp Die and paying particular attention to the inside surface of the neck. The Lee Collet typically has very low bullet grip, part of it's secret to low runout, most of the time only .001". That is why the Lee Factory Crimp is a good companion die to the Lee Collet, it will stabilize bullet release with the low bullet grip the Lee Collet produces.
Also I steel wool the hell out of the inside of the neck
and use mica
Using the Lee Collet, steel wooled and mica'ed necks, crimped with the Lee Factory Crimp the last 6 loads recorded on my 6.5 rem mag were 3072, 3086, 3072, 3072, 3072 & 3072.
However very good results can be achieved with the bushing die with a .003" bullet grip, steel wool and mica'ed necks but without a crimp the last 6 loads recorded on my 338RUM were 3191, 3182, 3182, 3189, 3189 & 3197.