Short 10 Velocity Question
 

I had loaded up some 1 1/4 oz loads using a published and tested recipe of Longshot, Ched hull/primer, Rem SP10 wad, one 1/4" and one 1/16" cork filler wad and an overshot card. The recipe listed the velocity at something like 1230 FPS. I backed it off a grain or 2 and the chrony had it at 1190 FPS. Perfect!

Then I decided to try an 1 1/8 oz payload with the the same recipe. Other than the shot charge the only things altered were the addition of one more cork 1/16" filler for stack height and the elimination of the overshot card. I expected the velocity to increase but to my surprise it dropped to 1080 FPS. I did not chrony both loads the same day to validate this but both were done under conditions favorable to the chrony. How can this be ???

Lower pressure causes less reliable ignition. Go to a faster powder for the 1 1/8 ounce load and the pressure will go up a bit and you'll get more reliable ignition.

I have excellent results using Unique for my 1 1/4 and 1 1/8 oz loads. Soft shooting and they break birds.

I shoot 700-x, 18 grs for 1oz, 19 grs 11/8 th oz and 22 grs for 11/4 oz.
Scott

Do you happen to know the FPS and PSI on those loads Scott ?

1 oz 5700 psi @ 1096 fps
1 1/8 th oz 7000 psi @ 1151 fps
1 1/4 oz 8700 psi @ 1225 fps
I did not check these load my self, I found these
in spread sheet and the 1 1/4 oz out of a old reloading book. I have been shooting these loads
for years. All sound good and very clean burn.
Scott

The original topic concerned the effect of dropping shot charges and it's effect on velocity. Most reloaders often take a normal mild load and lower the shot to get an effective light load at lower pressure. I was just afraid your original post would be misunderstood as to it's meaning. It is obvious with this response that it represents 3 different classes of load intensity that work.

You need more powder with less shot. Sounds crazy, but for a good balanced powder burn, try more.