Cheddite Primer pressure spikes

[Gary Laudermilch]

I previously presented some 20 ga test data using Cheddite primers and the results were concerning, at least to me. So, I did some follow-up testing. My initial test set did not include a load that matched published data. This test set does. As previously stated I have shot in excess of 50k shells loaded with published data and never thought anything of it as I trusted the published data. The Hodgedon site lists the following load

Remington STS hull
17.0 grains of WSF
WAA-20 wad
7/8 oz shot
Win 209 primer
1200 fps
10500 psi

I submitted this load for testing. The only exception is I substituted a CB-1078 wad for the Win AA wad. So, not quite apples to apples but close. The first data set listed are the results. Not quite a match. Well, not even close. The second data set is one I did earlier with Cheddite primer. I repeated it here so you can make a side by side comparison..

The following two data sheets are with Cheddite primers with much reduced powder charges. The 15.0 load is a full 2 grains below the published data above or nearly 11% and while the velocity is approaching the published load the pressure is still well above.

This data was intended to serve my needs and curiosity. It may provide some insight for those of you that are forced to use Cheddite primers.