Lawfficer-
The OAL for the 300-221-fireball running in an AR15 is about 2.255 in. They have to be able to fit in the mags... I am certain that an OAL of 2.65" that you listed in your post will not fit in AR mags. If you check the web site:
http://reloadersnest.com/frontpage.asp?CaliberID=135
All of my loads are listed under the "Not Yet verified user loads". My loads are for the following powders:
winchester 296
H4227
Lil'Gun
H110
I have included the OAL for all of the loads that I posted. The brass that I make from .223 brass, I trim to 1.400 in. The brass that I have that I made from necked up 221-fireball brass is shorter.. 1.366".
One last bit of info. My 300/221 olympic arms AR15 upper has the gas port in the pistol position.
I hope this helps.
320pf