DISCLAIMER: These procedures are intended for custom rifles
or those about to be made. Factory chambers and factory barrels are not
included within these steps. These are bench rest shooting loading procedures which may get the loader into dangerous or excessive procedures
unless you are experienced in reading pressure signs!
Now that ONLY seasoned reloaders are going to follow these steps, we are moving ahead predicated upon the fact that you are only using cases that have been fire-formed cases TWO OR THREE TIMES that have been fully preped and sorted. Two types of procedures:
A. Verify all powder charges that produce an accuracy velocity node. Meaning there is a velocity that is accuracy optimum for the bullet you are using and your barrel. Nosler and Hogdon manuals and web pages are but two sources of many to find powder charge candidates for nominal accurate loads.
B. Fill case with selected charge ( within 0.1 grain accuracy).
C. Seat UNIFORMED LENGTH bullet so that it is just touching the lands.
D. This is the Highest Pressure Load Length.
E. Measure and record velocity. If below Accuracy Node Velocity, go up in .5 grain powder increments until measured velocity is close to accuracy node velocity.
F. Check for pressure signs on primer, bolt lift and case.
G. Repeat E and F until at the desired Node Velocity and measure the group.
H. Shorten the LOA by 0.005" with uniformed length bullets and shoot another three shot group and measure it.
I. Continue H until a sub .5 moa group is reached. With match grade bullets continue until about a .2 moa group is reached.
J. Increase powder charge in .2 grain increments to shrink group.
Example, if you are loading for a 300wsm with 190gr SMK bullets, the accuracy load velocity is ( for example only ) 2,800fps with xx.x grains of H-4350. You load and get below xx.x feet per sec. Increase charge until limited by pressure or accuracy.
1. Per A-D above, measure and record velocity.
2. Load in .5 grain increments so that there are 3 loads of "touching length" as trial load #1.
3, Make 3 loads as base load +0.5 grains, 3 loads as base load plus 1.0 grai etc. up to max pressure loads.
4. Shoot and plot. Where one load impacts in the same cloverleaf as the prior shot, you have an accurate load.
I hope this clarifies how to get to the most accurate load for your rifle, your brass, your chambering and your bullets with cases preped your way.