Dean - The bullets that are loaded in the pic above are 300 grain Remington HP's. Don't know actual muzzle velocity yet, but once I settle on a load I'll run them across the chronograph. However, the muzzle velocity of these particular bullets with the powder I'm testing, Accurate Arms 1680, should be somewhere between 1850 and 1950 fps which will put energy levels around 2280 to 2500 ft/lb.

In addition to the Remington HP's I have some Hornady 300 grain HP Interlock and Barnes 300 grain TAC-TX. The Barnes cannot be pushed as fast since it is a much longer bullet with a corresponding longer bearing surface.

The SOCOM is a relatively low pressure round with max operating pressure set at 35,000psi. Test loads have to be worked up carefully watching for pressure signs. If you see a flattened primer (which will start flattening around 40,000) you're already past safe working pressures.

My upper is a 16" RRA mid-length gas system. If I had done a little more research before ordering I would have ordered a carbine length gas system. It makes a difference in reloading since the carbine length allows you to use powders such as H-110 and Lil Gun to get some higher velocities. The pressure curve on those powders peaks quickly and by the time the bullet has passed the gas port, the pressure has dropped to the point where those powders won't (in most cases...) reliably cycle the action on a mid-length. I will try H-110 though just to see if my mileage may vary.