I would appreciate some info on calculating my muzzle velocity.
I shoot Hornady factory ammo out of my .22-250 and have the factory provided ballistic info for a 24" barrel. However, my rifle has a shorter barrel (21 inches) and the online ballistic calculators I've found do not allow me to plug-in my barrel length into their calculation variables.
The ammo is: Hornady Varmint Express, 50 gr. V-Max
Is there a rule of thumb (estimate) for figuring each inch of barrel length affecting muzzle velocity?