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This month I want to talk about using the Stoney Point Cartridge Overall Length Gauge. This gauge enables us to measure the exact length of our loaded cartridges from the bullet’s ogive to the base of the cartridge case.

Rifles can vary considerably in the length of the throat. (the smooth portion of the bore between the end of the case neck and the beginning of the rifling lands) They can also be very particular about the distance of bullet jump from the case neck to the rifling. By varying the distance the bullet has to jump, we can often increase the accuracy of our handloads in a given rifle.

This is where the OAL (Over All Length) gauge comes to our rescue! Use of the gauge allows us to experiment with seating depth, and more importantly, to duplicate the exact distance that gives the best accuracy.

First, just follow the clear instructions that come with the gauge to determine the actual length of the cartridge when the bullet is touching the lands. Record this measurement, as it becomes the base line for knowing exactly how much we are manipulating seating depth.

Note that this requires a caliber specific "Modified Case", a bore size specific "Bullet Comparator Insert and Body", and an accurate dial caliper. All are available at major shooting supply stores. My favorite supplier in Spokane is Sportsman's Warehouse. They have several locations in the Northwest and you can visit their web site at
www.sportsmanswarehouse.com to see if there is one near you. (These guys buy in such quantity that they can usually sell you this stuff cheaper than the manufacturer will.) You can also check out Stoney Point's web site at www.stoneypoint.com should you elect to order directly from them.

Bench rest competitors have found that seating bullets from 20 to 40 thousandths of an inch short of the lands will often give the best accuracy for a given load.
However, only shooting YOUR rifle with YOUR load will tell you for sure which OAL gives the best groups.

CAUTION: As always, the load you are using may not be safe in any firearm other than the one used to develop the load. Also, seating bullets directly against the rifling can sometimes increase the pressures to dangerous levels for an otherwise safe load!!

Another consideration for repeating rifles, is that the magazine length may limit the OAL of the cartridge, so be sure and check this as you go. We, of course, want our general hunting ammo to cycle through the magazine, but, if a longer length proves to be a tack driver, you can always single load those for target or varmit shooting.

The rifle I am using for testing the OAL gauge is a Ruger Model Number One single shot in .25-06 caliber. With this rifle I am using the gauge for bolt actions or single shots with straight on access to the chamber. There is also a curved model available for use with lever action, pump, and semi-automatic firearms.

I won't publish specific load data, but I can tell you the load I am using in the Ruger contains a 75 grain Hornady V Max bullet over Hodgdon's H-414 Powder. My chronograph clocks the load I am using at about 3550 fps 12 feet from the muzzle of the 26 inch barrel.

I plan to start my testing with the bullets seated to a depth that gives the cartridge the same length from case head to bullet tip as a factory round. I will then seat further out in .010 inch increments until I am .020 inch from touching the lands. As I shoot groups for each seating depth I should find the right formula and then be able to repeat that depth for my most accurate load with that set of components.

It should be noted here that some bullets in light weights for caliber, may not be long enough to give the case neck a good grip when seated close to the rifling, so watch for this also. I may have this situation with the 75 gr bullet I am using. We shall see!

I'll report on the range testing with the olRuger in a future newsletter as soon as I finish the project.

So. . .
Til next time, Keep ‘em shootin’ straight, shoot ‘em often, and above all, BE SAFE!!!!!

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