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Muzzleloading Shotgun Velocities

posted Jul 21, 2010, 10:22 AM by Peter Lucas   [ updated Jul 27, 2010, 8:48 AM ]
Finding published data regarding the velocities of various black powder loads in muzzle loading shotguns is not easy.   One of the few good sources of velocity data which I have found is the
"Lyman Black Powder Handbook and Loading Manual."  The Lyman Handbook has been my primary source of velocity estimates over the last several years.  However, I recently borrowed a chronograph and I was quite surprised by how far my actual velocities exceeded the velocities published in the Lyman handbook.

    My methodology was pretty straight forward.  I started by shooting a five shot string with my Browning Lighting using Federal game loads which had a stated velocity of 1290 fps to check the accuracy of the chronograph.  The average measured velocity of the five shot string with the Federal loads was 1310 fps; or only 20 fps higher than the advertised velocity.

    Next, I fired a series of five shot strings with my 12 gauge Underhammer trap gun.  I started with One Ounce load with 2.5 drams of Goex FFFg. The amount of powder was increased in one quarter dram increments for each shot string.  No testing was conducted with heavier shot charges.  The wad column consisted of one nitrocard over the shot and one over shot wad.  I fired a similar series of five shot strings with my 12 gauge Pedersoli SxS.  Finally, I shot another string of Federal game loads to confirm that the chronograph was still reading accurately.  (There was a pretty good layer of black powder grime on the sun shades of the chronograph).

    The results from the tests and the corresponding velocities published in the Lyman handbook are included in the following table. 

Velocity of One Ounce Loads
grains drams Lyman Handbook Goex FFg 26" barrel Pedersoli SxS Goex FFFg 28" Barrel Trap Underhammer Goex FFFg 33" barrel
68.4 2.50 1090 1152 1141
75.2 2.75   1151 1158
80.0 2.93   1162  
82.0 3.00 1160   1198
88.9 3.25 1170    
95.7 3.50 1180    
102.5 3.75 1200    

    It is interesting to note that both guns produced significantly higher velocities than what would be expected from the Lyman Loading Manual.