Posted by denny mcdaniels on May 23, 2025 in Rifle Cartridge Reloading
Writing by John Nosler on page 151 in the Nosler Reloading Manual Number ONE on how to determine at what point a bullet comes in contact with the rifling so maximum overall cartridge length. The only tools required is a set of calipers, empty unprimed case, the bullet that you wish to reload for, and a cleaning rod.
1-The first step is to insert a bullet through the chamber and make firm contact with the rifling. Then insert a ramrod from the muzzle all the way until it comes in contact with the bullet tip. Now mark the ramrod with a marker, this established the distance from the bullet to the muzzle.
2- Remove the bullet and close the bolt on an empty chamber. Again, insert a ramrod from the muzzle and have it rest on the bolt face. Mark this spot on the ramrod, the two markings represent the maximum overall cartridge length which allows the bullet to just contact the lands.
3- Assemble a dummy round (no powder and primer) to that length and test, you want to establish that this length will indeed allow the bolt to close and that no rifling marks appear on the bullet. If there is rifling marks, seat the bullet deeper. The end result is your max COL, from there experimenting is still advised to determine what is the best overall length for that bullet.
I used this method in working up a new load for a 270 WSM. The bullet is Speer 150-grain Grand Slam that was loaded into Hornady #8637 270 Short Magnum brass cases. This particular rifle being used is a Kimber Model 8400 Montana. I measured a COL of 2.835 inches. I intended to use a fairly warm powder charge of 55.7 grain H-4350, with that in mind I wanted to back the bullet of the lands .025 inches for initial testing. This load has average MV of 2879 fps with spread of 29 fps. Happy with the results speed wise, next trip I want to try a few rounds that are slightly longer to measure any noticeable difference in group sizes.
Denny McDaniels