Lighter Pellets Travel Faster? Comments Welcome

[gamyrick]

I ordered 10,000 of the .22 caliber, 12.65gr, H&N Baracuda Green Pellets. The order was split between 2 different vendors. When the first order arrived there were several tins marked 12.5gr and when the second order arrived there were also several tins marked 12.5gr. I contacted the vendors and they both offered to exchange the pellets for the 12.65gr and assured me that the .15 grains would make no discernible difference. This weekend I decided to chronograph the 12.5gr pellets and I was surprised. The lighter 12.5gr pellets did not perform nearly as well as the 12.65gr pellets. 

12.50gr - Average Velocity = 719fps, Extreme Spread = 11, Standard Deviation = 4
Head Diameter = 5.49 - 5.50, Skirt Diameter = 5.65 - 5.75, Pellet Length = 8.34 - 8.55

12.65gr - Average Velocity = 728fps, Extreme Spread = 4, Standard Deviation = 1
Head Diameter = 5.48 - 5.49, Skirt Diameter = 5.72 - 5.74, Pellet Length = 8.24 - 8.28

 

[ajshoots]

The addition length of the lighter pellets could be part of the issue? Are they the exact same alloy as the 12.65's? Having a slightly larger head diameter could explain some speed lose as well.

In .22, polymags shoot faster in my guns than crosman premiers and the premiers are lighter. I have always assumed maybe the harder lead of crosman pellets is the cause?

 

[gamyrick]

Yes, both pellets are tin. I believe that you are correct and the longer length is the reason. I'm surprised that it only takes a fraction of an inch to make a difference.

 

[bill_dd97]

Do the 12.5s have a longer skirt?

 

[gamyrick]

I didn't measure the skirt length. I only measured the overall length. I'll measure the skirt length tonight and let you know tomorrow.

 

[gamyrick]

Yes, the 12.5(s) do have longer skirts.

 

[bill_dd97]

I think the longer, narrower skirts aren't engaging the leade, causing a slight leak before the skirt expands to fit the barrel.