Cheddite Primer pressure spikes

[Gary Laudermilch]

After reading this thread and others on different forums relating to pressure increases with Cheddite primers it has raised some concerns. There are plenty of anecdotal comments that suggest Cheddites and Win primers are interchangeable. Data presented seems to indicate otherwise. So I decided it was time to do some testing.

My to to powder for 20 ga has been WSF for decades. I have shot in excess of 50,000 of the load published on the Hodgedon site in all kinds of weather and patterned them extensively. The only substitution I made was using a Claybuster 1078-20 wad for the Win wad.

So, I sent my standard load of 16,8 gr. of WSF off to Precision Reloading and just for the heck of it included a load at 16.3 gr of WSF. Both loads substituted a Cheddite primer for the Win.

The Hodgedon site lists 17,0 gr for 1200 fps at 10,500 psi.

The results are attached.

Addtionally, my son had 600 shells loaded with 20/28 and Cheddite primers so we sent them as well. Alliant lists his load of 15.5 gr at 1200 fps and 1010 psi with the CB wad.

All loads were scale weighed to be exact. In retrospect I wish I had included shells with the Win primer as a baseline and to confirm the published data.

Draw your own conclusions.