I know there is a chart for powder burn rates,is there a chart for how hot primers are? The reason is I done some testing today with my 500JRH and got some interesting results.With a 400gr bullet over 10grs of 231 the accuracy was best with Fed 150s followed by CCI 300s then WLP then CCI 350s. Then a 400 gr bullet over 15grs of HS-6 it changed to CCI 300s,WLP, CCI 350s then Fed 150s. From a recoil stand point the fed 150s recoiled the least followed by the WLP a little more and CCIs the most of what was used. Accuracy differences weren't huge but noticeable,shots were rested @25yds. anyone ever noticed differences like this?

I've not tested it but I read an article a few years ago that stated that njust by changing primers you could increase pressure by over 6000psi

I've read a few articles stating the same thing. That is one reason I guess that you start low and work up with load development, and the use of a Chrono is recommended. Other than that the only way to be "in the ballpark" is to use the exact components that each published, and researched, load recommends. How many of us actually do that ALL THE TIME?

Yes, some powders do not need a mag primer.
I use mostly 296 in the JRH and .475 so I use the Fed 155. The reason is case size that can handle them with 296.
In the .44 and .45 Colt I use a Fed 150 with 296.
I never figured out if one primer is actually "hotter" but some seem to have more primer pressure.
I suppose the best way to see is to load with no powder using each primer to see how far out they will push a boolit.
I like fire but not pressure in the revolver. Some primers in some calibers can break the brass hold, move a boolit, before full ignition.

My Magnum Research 454 is very particular with primers. It likes CCI Sm. rifle primers the best and Remington No. 7 1/2 second and Federal Sm. rifle primers the least.

Very interesting, 430man. It makes sense; would be an interesting experiment and would like to read the write-up on it.