Howdy Medic,
Disclaimer: I am not a member (yet). But the rules are all at NCOWS.com
All I see about load limits is:
"No squib or magnum velocity loads. No jacketed bullets, only cast lead alloy only bullets. Shot is to be lead only, and no larger than #7 1/2’s. Only cartridges and velocities approved in The Tally Book are allowed. Shooters may be held responsible for damage caused to a target by too “hot” a load. "
And then in the Tally Book we find:
"10-2. Smokeless powder loads shall not exceed the maximum muzzle velocities of comparable black powder loads, e.g. 1500 fps for single shot cartridge rifles; 1300 fps for lever action rifles; 1000fps for handguns. Smokeless loads may be chronographed and certified by the Judge before the shooter will be allowed to compete. No loading below manufacture’s recommendation. Minimum velocity for any main match firearm is 600fps or published loading data. "
So looks to me like most BP loads should be fine, unless you are using a heavy powder charge under a lighter than normal bullet which might exceed velocity limits.