Single shot LR rifle is no handicap. The O.A.L. should be driven by accuracy unless there is a reason to have to feed up through the magazine. Ditto's to the others who pointed this out. You have to think outside the box (magazine).
I use an old school method that still works. No case required. Needed:
Selection of bullets
New pencil w/ erasure
Cleaning rod
Cleaning jag w/ flat tip. Cut off any pointy thing and make sure it's flat and square
Drill stop collar the diameter of the cleaning rod. Looks like a short round nut w/ slit and bolt to clamp around the rod
Measuring Caliper
1)With the bolt in the gun put the rod/jag down the bore from the muzzle with the stop collar slid up to the rod handle. Slide the drill stop down and carefully tighten the collar flat on the muzzle with the rod/jag pushed against the bolt face. This is your barrel length and case head location. The bolt should be cocked so the firing pin does not protrude.
2)Remove the bolt from the gun and push a bullet into the lands lightly with the eraser side of the pencil muzzle pointing up. You have to juggle this around to do it with one hand. I spring clamp the gun to a table. The rod/jag should move freely up out of the barrel. Move the pencil up and down to lightly contact the rifling with the bullet, the bullet should be able to move back and not be held by the rifling.
3) With the caliper measure the distance between the muzzle and bottom of the stop collar. This is the O.A.L. of the round to bullet engagement of the rifling, e.i. "jammed".
You can do every bullet in that caliber in ten minutes. I write that measure for each bullet inside the top of the reloading die box on a shipping label.
You do this because it is possible to have a bullet that "jams" before max cartridge length in reached. Nosler has a warning using the 375 cal 260gr Partition in the 375 Ruger. Can't use the crimping groove or it may jam tight raising pressure. In my barrel the Nosler jams @ 3.331" and w/ 2.580" brass and bullet crimped into the groove the C.O.A.L. is 3.300" for a jump of 0.031". Just got lucky as Savage uses a different throat leade than Nosler's test barrel.
Most reloaders never do this important step. It speaks well of you that you are pursuing this step.
KB