Did he test Rem 2 1/2 if so, where did they rank?

Frank

I use Remington primers since they have the longest and hottest flash as per the testing printed years ago in Precision Magazine.
Winchester and CCI were next and the coolest and shortest flash was the Federal primers.

For my small rifle primers I use R.P. 7 1/2 with smokeless powder.

For Black Powder I use large rifle magnum primers R.P. 9 1/2 M.
The magnum primer ignites and burns up the fouling in the barrel. Any primer will ignite B.P. and any ignition is going to move the powder in the case.
I believe complete ignition and complete burning and reduced fouling from magnum primers is more important than using pistol primers for reduced ignition.
That is what my rifle testing has shown when I used compressed powder of .240 inches and where I have reduced fuse problems in the flash hole with newspaper wads over the flash hole inside the case.

This confirms Mike Venturino and Steve Garbe recommendations of using magnum primers in their BP Cartridge Reloading Primer (pg. 19).

Because knowledge and practice are continually evolving, it is a good idea to read the works of writers like Venturino and Paul Matthews in the order they were written.

The primer question is a "prime" example.

Paul

The guys shooting varmet class all prefer sp and small flash holes. 6ppc, 6br and so on. I have made some 6ppc out of military brass with large primer and flash hole. Couldn't see much difference, probably just me and my old eyes😪

Larry

Will let Steve Garbe know. He is under the impression that MLV still prefers 215M.