The shape and style of a bullet is also impertant. The 'Ogive' is a very important factor that determines OAL (over-all length). The Ogive is the shape of the bullet from it's tip to the point where it it is full diameter of the bullet. Some are basically straight, and some are curved, this will change the length of the thicker part of the bullet and where it engages the rifling. For instance, if you are using data for spire-points, you will not want to load something like a wad-cutter to the same length. It is pretty simple. This is what I do, take a spent case, and insert a new bullet in the neck, leave it as long as possible. If it dosent stay in the neck of the case , just bite the neck a little or squeeze it sligtly oval with a pliers. The idea is to just hold the bullet with a little pressure. Then gently chamber your dummy round, and remove it. Measure the OAL, and this will tell you where THIS bullet is engaging the rifling. I do this a few times to make sure it is consistent. I usually back off .010 from that length...some target shooters like it tight. If you are using hard-cast and lighter loads, I would back off even more.
Also...pressures can change with different bullets, ie, round-nose or pointed etc. Solid Copper like Barnes X should ALWAYS be loaded with specific data for that bullet.
Just remember the golden rule. Most books have a starting load listed, use that and work your way up .5 grs at a time. Maximum loads listed are seldom the most accurate load for your rifle.
