Originally Posted By Mongoose16:
If you don't know your chamber dimensions and how much free bore you have with a particular bullet, don't load longer than the max C.O.L. listed in the reloading manual.
That is the key. I reload for my AR-10 chambered in 243 Win, and I shoot most of my heavier bullets .020 off the lands or closer. That being so, I am still shy of reaching my max mag length, which is intended for a 308 round at 2.800" oal.
For best function along with accuracy in my rifle, I settled on H4350. Most powders faster than the 4350 would not cycle my action properly. It may be different with your gas system in the DPMS.