Magnum Small Pistol Vs. Small Pistol Primers in 9mm Luger?

[Doug B.]

I have some magnum small pistol primers (which I would like to "burn up") and the reloading data I have found recommends small pistol primers for 9mm Luger. The following is Accurate Arms data for their AA-7 powder for 115 gr. Rainier round nose bullets with a Winchester small pistol primer:


                                Start        Vel.        Max          Vel.        Press.        C.O.L.
                                Load                      Load                      (p.s.i.)       (inches)
                                (Grains)                 (Grains)                                             
No 7 115 RAN RN      5.7           1,027     6.7           1,165     34,399     1.140

Here's my question: If using magnum small pistol primers verses small pistol primers, how much of a powder reduction would you recommend to keep me safe? I have heard from only one source to reduce the starting load .5 grain for starters.

I instinctively "start low and work up".

The magnum small pistol primers I would like to "burn up" are CCI no. 550's and the firearm is a Beretta PX-4 Type F semi-auto with a 4" barrel.

Suggestions?

Thank you.

[bobthenailer]

i have used mag pistol primers in 38 super/ 9mm and 45 acp without any problems !  i picked up alot of fed  mag pistol primers a few years ago at a good price . The loads i was shooting was not at max ! usually at least 1 gr under max.  all i did was switch from fed sp to fed spm.
I have shot at least 10,000 rounds  this way, with most being 45 acp and in most cases you would have to shoot from a rest at 25 yards to notice any difference in accuracy.  just my findings

[shot1]

With ball powders it is best to use mag primers because they are a little harder to light. My Accurate #2 manual list this data for 115 (Lead) bullets. Start with No.7 is 7.8 grs max is 8.7 grs. With Jacketed bullets start with No.7 is 7.9 grs max is 8.8 grs.

I would not lower the start load any. Just use the mag primers and the start load and work up until you get accuracy and stop there. You usually find best accuracy a little under a max load.