Regarding the use of small rifle primers...
Digging & research has shown us that for CCI brand primers (I do -NOT- know about any other brands), the CCI-400 Small Rifle (non-magnum) and the CCI-550 Small Pistol Magnum primer... are the SAME product in different packaging.
I do not know if the 400 is harder to ignite, but I would suggest that it is-- part of the make-up of a rifle and/or a magnum primer isn't simply a longer burning/hotter flame, it's also a sturdier cup to contain higher pressures. The primer is a weak spot for containing pressure.
FWIW, the .327 Federal Magnum handgun cartridge was designed specifically around a magnum pistol primer as the cartridge runs a SAAMI max pressure of 45k PSI. Federal has only ever loaded the round with a magnum primer.
Many folks have transitioned to using small rifle (non-magnum) primers and eliminated the small pistol non-magnum primer from their inventory. and if you are loading handgun ammo using the popular H110/W296 (I don't) or Accurate#9 (I do!) than you truly should be using magnum primers for your loads.
Further mucking things up (but not for small pistol primers) are Winchester's WLP, for which they state on the packaging "for regular or magnum pistol loads" and it appears they don't even offer a non-magnum large pistol primer anymore.
CCI primers are well known in the game to have some of -the- hardest cups, and are some of the most difficult to detonate. As it turns out, I also ordered a Wolff spring kit for my GP-100 which is chambered in... (you knew it was coming!
) .327 Federal Magnum
and I did indeed have some light strike problems with the lightest hammer spring when shooting double action. I believe I'm a couple pounds under stock now and running well. CCI-400 primers exclusively in this round.