Not to choose sides here..i had a similar discussion with BFR last year. So being the stubborn hard headed person that i am i set out to prove him wrong. I started an all out primer testing fiasco of my own. I bought every brand primer i could find, even some old remington from the 60's a friend of mine still had. I tried, unique, bulleye, Imr4227, 2400, 296, new brass, once fired, and "darn near worn out brass" Hell I had a Western Sizzlin buffet of 44 mag garb loaded up. in all reality i got tighter groups(not much) with well used brass and LP primers than I did with any other brass/powder/primer combination. My final load ended up being 2400/federal #150/well used starline brass/ 240 keith bullet/ Ruger redhawk 7.5 1981 model. All of my testing was this summer so i have no temperature comparisons. most days testing were 95*+ and all was done between 25-50yds outside off of sandbag/ shoot n clean. Further testing to come in cold weather. Dont know if it means anything or not but he was partially correct about the issues we argued then. I feel overall that my abilities as a shooter were more important than all the other crap combined and in the long run any of the loads would have been more than accurate enough to down a white tail. My S&W 500 uses only LR primers and you can bet it'll never see an LP primer in it i can tell you that. Nor will any of my rifles ever see LP primers. I have never loaded 45 acp with SP primers and doubt i ever will. I doubt any auto in 45 acp would ever know the difference. If it does i wont be there to see it. Some of my best groups with my Colt pre series 70 National Match was with white box wal-mart ammo. I have a series 70 LW commander that nothing will shoot good in. I guess i never intended to be as accurate with my 1911's as i am with my big bore revolvers.
I like that, that you tested. That is important and what I ask. I get out of sorts when all manuals say you NEED mag primers.
The 1911 can use both the LP and SP primers because it is not a revolver. Yet there might be a tiny accuracy advantage with the SP primer and evidence is the amount of cases found cut for the SP primer.
I don't like to argue at any time. I present my findings for everyone to try, nothing is cut in stone. Just think out of the box to see if it works for you.
Many dispute and that is fine but you have to test first. Others dispute to keep an argument going forever without ever knowing a thing about it. Do the work, see what works, it might be different then what I found and I will agree with you.
It is the sharing of experience that just might help someone that is important and personal stuff needs to be left out.
None of us shoots the same stuff so results change.
Now the .500 S&W CAN use a LR primer as the case is large. My caution is to make sure your brass was not cut for a LP primer because there is brass out there. THAT IS DANGEROUS if you use a LR primer. Measure pocket depth if you pick up brass. You can cut the pocket deeper with a tool. Your safety in my concern.
