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Cartridge Overall Length
Cartridge Overall Length (O.A.L.) Determined
The overall length (o.a.l.) listed on the drawing in Modern Reloading is the SAAMI (Small Arms Ammunition Manufacturers Institute) specification. Most of the load data in the book was supplied to us by the powder manufactures. One can exceed the recommended maximum overall length as long as it doesn't interfere with the function of the rifle. If your rifle will not accept ammunition loaded to a longer o.a.l. choose a different bullet/powder combination.
There are many tools on the market to determine the "free bore" of your particular rifle. This is the distance from the face of the bolt to the lands of the barrel. A handy way to determine this without such equipment is to use a fine marking pencil and a cleaning rod. Use something to make the internal portion of the threads of the cleaning rod blunt so that a tip of a bullet cannot go into the concave portion. Even a piece of Duct tape will suffice temporarily. With the bolt out of the gun and the bullet you intend to use placed and held up against the lands and grooves of the barrel, place your cleaning rod in from the muzzle until you feel it stop against the tip of the bullet. Mark this spot on the cleaning rod from the muzzle end. Remove the bullet and repeat the procedure with the bolt in and closed. The distance between the two marks will be a close indicator of the maximum Cartridge Overall Length for that particular bullet.