If I remember correctly, shortly after I bought my Springfield .45 Super V-16 a shop called Ace Custom .45's in Texas got a registered trademark on the ".45 Super" name. A lot of manufacturers wouldn't pay the royalties to Ace Custom .45's to use the ".45 Super" caliber name or SAAMI specs for new guns and the cartridge really sort of died out as a result. Buried on my shelf I still have some old Triton .45 Super ammo that I bought from Sportsman's Guide when they got rid of it after the trademark issue, and I believe I have some other factory stuff from somewhere else. Once Ace put the clamps on the .45 Super name the only place I see headstamped .45 Super cases was from Starline. I don't think that's why there is a +P+ headstamp on your .45 ammo, though. (If it is stamped that way, I may be confused on the above post and it's only the 9mm that's +P+. I haven't ever seen/heard of +P+ .45 ACP ammo.) The 9mm +P+ ammo I have is headstamped "WCC" with two digits for the last two digits of the year of manufacture (So "WCC 16" would be made in 2016, etc.) My experience with Winchester 9mm +P+ is that it is a specific ammunition performance standard sought by a large-quantity buyer (In this case my local 2,000+ sworn Sheriff's office), and this standard will often exceed the SAAMI pressure limits of +P ammo. I was told by an armorer there that their office has gone away from the +P+ during the past year or two because manufacturer warranties on guns weren't being honored with +P+ use, so they're now issuing the 124 gr +P Ranger SXT load for 9mm. They haven't had a reported drop-off in critical-incident performance that the armorers could recall. I have a lot of swap-out Winchester SXT +P+ loads on my shelf, every year I would get at least two boxes to replace the duty loads in my duty Glocks. I've kept the swapped-out ammo boxed up as spare ammo/carbine fodder. It shoots really well out of the Ruger PC9. (I found this after I wrote the above, it's pretty much the same story on the .45 Super and Ace Custom that I wrote about http://www.45super.com/ ) Stay safe.