Question on tables in Lyman 48th Handbook

[CBP]

I was looking over the load tables in the Lyman 48th reloading manual and was curious what the letters BC and SD (upper right corner) stand for?

Also, their stated OAL for the bullet, is that the suggested overall length, the minimum, or the maximum?

I like some components of their tables, especially the drawings of the bullets. I'm using cast lead bullets from a local supplier, Moyer's Cast Bullets, so I can verify the bullet I'm using. Take the .45 ACP for example. They list two different 200 gr. bullets, but the starting loads vary quite a bit between the two as well as the OAL. By being able to look at the shape of the bullet and the number of grooves, I am pretty sure I'm using the bullet on page 357.

I think I still like the Lee Handbook a little better, even though I'm somewhat guessing on the bullet type. It seems to be a little more conservative on the powder charges, but I'm looking for plinking loads anyways.

Now that I'm getting started reloading, I understand why many reloaders have several handbooks and also use the powder companies information available on the internet. There is definately variation in the loads.

 

[rcmodel]

BC = Ballistic Coefficient.
SD = Sectional Density.

Suggested OAL is generally determined by what fits in standard length magazines, feeds best, or where the crimping groove is on the bullet.


rcmodel

 

[azar]

SD stands for sectional density, which is basically the bullet weight in pounds divided by it's square in inches. Shape doesn't matter for SD because all bullets of the same caliber and weight will have the same SD. Sectional density is a means some people use to roughly measure a bullets ability to penetrate game. The higher the number, the better the penetration. You can read more about it here.

BC stands for ballistic coefficient and it is a measure of how well a bullet cuts through the air (air drag). Higher numbers means the bullet has less drag. Ballistic coefficient is not constant however. It changes with velocity and is affected by the bullets shape. You can also read more about that here.

The O.A.Ls listed are basically the lengths tested with that load and so should be safe to use. Reducing the O.A.L. could cause unsafe pressures but you can always seat a bullet further out. How far you can seat a bullet out may be limited by the size of your guns magazine or other factors. Most reloading sources say unsafe (too high) pressure will result if you seat it far enough out that it contacts the rifling. But seating it "just off the lands" will give the best accuracy. Determining the best O.A.L. is an exercise for each different bullet type for each different gun.

 

[CBP]

Thanks for the info on the abbreviations. I didn't think the numbers were anything that I had to worry about for the time being. I'm just getting started in the reloading business and am currently only looking to produce ammo that safely hits the target. That data might be of interest down the road though.

Determining the best O.A.L. is an exercise for each different bullet type for each different gun.

I was downstairs working on that "exercise" just a few minutes ago, at least measuring the longest bullet that will drop in the chamber of my .45's. I'm going to mark those numbers down so I can play with the OAL in the future.

Thanks again for your assistance.