I know an M1 carbine has an 18" barrel Cartridges of the world says 1900ft/sec with 110gr bullets and 14gr of H-110 powder therefore the powder must have a K of 2896. A 20" barrel would give 1951ft/sec.
A 34" rifle 54cal round ball(230gr) should go 1716ft/sec with 70gr of 2Fg The published figures for a 44-40 24" barrel is 1310ft/sec making K 1530 not 1544. This is still too high to give the published 1389ft/sec. The gun is flintlock and doesn't have a breech face and will leak pressure. Using the formula to find K for the gun (1250) I would expect an 8" barreled pistol with 35gr of 2Fg powder to give 724ft/sec. With a 222gr ball 735ft/sec is predicted. 792ft/sec is published in the Lyman handbook. Not a bad formula I think.
1389ft/sec comes from the internet. Lyman state 1409ft/sec for a 28" barrel and Geox 2Fg. Someone has a batch of poor powder.
Last edited by mikthestick; March 12, 2012 at 08:36 AM.