[electronrider]

I am starting my first loads now, and have been working with dummy cartridges to determine OAL for my AR. I am using Hornaday 68 gr. BTHP out of an AR15 24" barrel, 1 in 9 twist. I am finding that I can't really go over 2.250, that is awfully close to the length of my magazine. They feed ok into my AR, and they seem to be feeding ok through the magazine as well. When I measure my test cartridges, I get a bit of variance in the OAL, but when I measure the bullet, I see where there is a difference in the length of it, so I believe that's where that bit of variance is coming from. So, If I am running cartridges between 2.240 and 2.250, and they feed ok, is this about as good as it gets as far as tweaking the OAL for an AR?

[Bullet]

If you measure your bullets with a bullet comparator the measurements will more consistant because a comparator measures from the ogive not the bullet tip. But the way you have done it I believe is correct. When measuring from the bullet tip you have to allow for the variance in the bullets (meplat). When loading for mag length you have to allow for the longest bullet/cartridge to fit in the mag.