Benchrest shooters are notoriously meticulous. In order to shoot the mind boggling scores and groups these competitors do, every detail has to be accounted for. Here are six reloading items they check to help manage those details.
Check # 1: Check to make sure the tip of the bullet does not touch the seating stem of the die.
Seating depth is an important piece of the tuning puzzle. Seating depth is measured from the base of the case to the ogive of the bullet, not the tip of the bullet. Bullet lengths can vary. Even custom made bullets can differ in length. What does not change, as long as the same point up die was used, is the placement of the ogive on the bullet.
If the tip of the bullet contacts the stem of the seating die, then the seating depth could be off a corresponding amount. When the tip does contact the seating stem, take the stem and bullet to a machinist and they can get you fixed up for a small fee. For consistent seating, make sure the circumference of the seating stem contacts the ogive of the bullet.
Frequency: This is a one time check for each stem/bullet combination.
Check # 2: Check if the object is square with the measuring jaw.
Carpenters use tape measures. Precision shooters use calipers. When the exact length is to be measured, make sure the object is square with the measuring jaw. Any angle, and the hypotenuse is being measured.
To make sure the object is square with the measuring jaw, put the caliper up to a light. Any gap will be easily seen in the light.
Frequency: Every time a caliper is used.
Check # 3: Check there is a slight gap between decapping rod and bushing.
The bushing in the resizing die needs to be able to “free float”. This will ensure that it can self-center over the case neck. To make sure this is happening, shake the die. If a rattling sound is heard, the bushing has enough room to self-center.
If no rattling is heard, loosen the locking nut on the top of the die. Back out the decapping rod until you can hear the rattle. Re-tighten the locking nut. This will ensure the bushing can self center over the case neck.
Frequency: This should be checked each time the resizing die is screwed into the press.
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Check # 4: Check the Shell holder is sitting on plane A.
In order to make sure the case gets started plumb with the die, plane A of the shell holder needs to sit on the surface C of the press. If plane B is resting on surface D this could raise plane A.
An easy way to check this is to put a .002 feeler gauge between the bottom of the shell holder (plane B) and surface D of the press. If the feeler gauge goes in easily, then plane A is properly sitting on surface C.
If the feeler gauge does not slip in the gap, this could mean plane A is not resting where it should. Remove some material off of the bottom of the shell holder (plane B) with a bench grinder or belt sander. Do not worry about the looks of your work, there simply needs to be the slightest amount of clearance.
Frequency: This is a one time check per shell holder/press combination.
Check # 5: Check that the same press, shell holder, and resizing die are used.
Once the resizing die is set for the correct amount of shoulder bump, do not switch parts. The press, shell holder, and die all work together to give the correct amount of shoulder bump. If any of those three items are changed, so can the amount of shoulder bump.
Frequency: This should be checked each time a batch of cases are resized.
Check # 6: Check the diameter the bushing actually resizes.
The neck bushing might say it is going to resize to a certain diameter but that does not mean it always will. There could be several reasons for this. One is work hardening of the rifle brass. This physical repercussion of repeated firing and resizing influences the brass springback. Another reason; the bushing could have a layer of resizing wax on the inside. Or, the bushing might have been cut slightly off. Regardless of the reason, the bushing size has to be measured to be trusted.
Once the neck is resized, measure the outside dimension towards the top of the neck. This is the actual number the bushing resizes to. Do not be surprised if the bushing resizes slightly differently than what is printed.
I keep a record in the bushing box with the actual resizing diameters written on it. For multiple bushings with the same inscribed diameter, I color the top of the bushing and record the actual diameter with the color on this paper. During load development, I will record bushing size and color.
This is important because neck tension is another piece of the tuning puzzle. When you try a new bushing, you might think you are going up in neck tension, but you might actually be going down. The only way to know for sure is to measure the resized case neck.
Frequency: Each bushing should be checked and the actual measurement recorded. Check periodically after that.
Check out the YouTube video that parallels this blog
Consistent precision on the target is no accident. It is not luck or “just a good day.” Consistency is a by-product of unfailing attention to detail. Check these items before you reload and you will be on the path to shooting smaller groups. Until next time, enjoy the process.
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