When I have been seating my bullets not all of them come out as the same length. I am trying to seat them so the C.O.L. is 3.6" but they are coming out anywhere from 3.592" to 3.605". Is this normal or am i doing something wrong? I am shooting Sierra Matchkings and I trimmed all of them down to close to the same lenght.

Thanks for any help.

Pdawg,

Stoney Point (and others) makes a "comparator" that attaches to your calipers for measuring a cartridge (or just the bullet). The comparator measures from the ogive of the bullet as the measuring point. This eliminates the variations in readings a person would get because of the factors Prewar wrote about. I have a caliper that is dedicated to my Stoney Point comparator and headspace gauge.

Casey

if you order a meplat trimmer,..you will have exactly the same OAL AND same BC for each pill. It is a PITA but it will uniform all bullets in the lot.

Where does one find a meplat trimmer,i've got the same question. Does compression drastically change if COL is supposed to be 3.340 but ranges .010 up or down?

I usually find that the most accurate load is with the bullet almost touching the lands.
To find that, I hand start a bullet into a case fired in that chamber, but not resized. Then with a wooden match, I blacken the bullet. When seated, the lands will push the bullet back into the case. This can be verified by bright marks on the blackened bullet caused by contact with the lands. That is the absolute maximum OAL for that bullet and chamber combination. I usually start my accuracy load search about .010 less than that. I put a little superglue on the joint and store that cartridge with a tag that identifies the rifle and bullet. When I adjust the seating die, I put that blank into the shell holder and back off on the seating plug. Run the cartridge up into the die and turn the seating plug down onto the bullet. Lower the case and then turn another 1/8 turn and lock the seating plug down. Carefully measure the first loaded cartridge for length.
Remember, it is not unusual for cartridges loaded this long to refuse to work in the magazine! Also remember that if you load to the lands, don't do so with a previously determined max load. A bullet that touches the lands will result in higher preasures than one that has to make the jump.

David Tubb sells a meplat uniformer at his Superior Shooting Systems site.
JCN