I just wanted to share some results I just got back from pressure testing. I have a bunch of Federal tactical buckshot hulls that I wanted to develop a recipe for. They have a ton of room and appear to have a similar base wad to the 3" federal .090 basewad hulls. I sent in a load of 37 grains of powder and 1 1/8" of #3 with CSD 1 1/8 wad. I was trying to recreate a 3" load in a 2 3/4 hull. I sent in 2 sets to test. The only difference was one set had federal 209A primers the other had Cheddite primer. I had put the primers in first then reloaded both sets with powder, shot, and crimp all at once. They were both over pressure, but the 209A took it way over. The average results were: 209A primer 1669 fps at 16116 psi. Cheddite primer 1629 fps at 13352 psi. Since I have all 3 1/2" guns I am going to back down a bit on the cheddite primer load to get it a little lower on pressure and see how it patterns. So the moral of the story, be very careful with primer swapping, it can push you over pressure in a hurry.