Oh man, memories....
OK, back in the day, there was this group of guys on base that worked in this little shop across from ANGLICO onboard Lejeune. It was adjacent to the Recon boys, but these guys were moustachioed in such a way that made the Sergeants Major cringe, and they had a panache for wearing short blue shorts...
Anyway, they had cool toys. I never saw a MK23, but they had plenty of cool stuff. I did see a bunch of USP Compact .45's and a few 1911's that would make you cry. Well, it seems that most of the time they were training with he Recon guys, and the rest of the time they went to the range. It's a haul out to Stone's Bay from Main Side, but well worth the trip if they come asking. Keep in mind, these guys were like rock stars to all of us, especially this very moto 19-year-old Lance Corporal that looks and awful lot like a skinny me. So to the point of this... sorry, a flood of memories I have not thought about in years.
There were 2 kinds. Winchester made a 185gr .45 +P round with a truncated nose like a typical .40 round. I'd never seen anything like it. It came in very nondescript plain white box with the Winchester logo, off white styrofoam inset, 50 rounds per box. It has a red lacquer-like substance around the primer cap. The data on the side of the box indicated a muzzle velocity of ~1250fps. How do I recall this so well, you ask? They gave me an ammo can full. Years later I was trolling a Sportsman's Guide catalog (well before I started going on the internet everyday, circa 1999-2000) and saw what I couldn't believe. The same dang ammo! It was even advertised as Navy SEAL ammo!! or some such crap. I called and ordered all I could afford, which was like $16 for a 50rd box, and back then I think crapping $100 was tough. Myself and everyone I shot with marveled at this stuff. The muzzle flash was so purely white and sharp was not the word for the report. It burned cleaner than anything I have seen even since. Stuff was accurate as hell. Anyway, I didn't know about lot numbers and all that crap back then so I never kept a box flap. I simply figured I could just call around and find it, but alas since that ammo can and those 10 boxes were fried, I have never seen it again. Believe me, I have tried. I have called Winchester I do not know how many times trying to describe this stuff to no avail. I quit chasing that elephant 10 years ago I think.
And the other kind.. since it came up. I never saw any, but according to chit-chat among myself and the aforementioned gentlemen with whom I was honored to shoot the +P stuff in all its awesomeness couldn't (or they wouldn't, whatever) be shot suppressed due to the muzzle velocity, so Winchester made a SECOND bullet identical to these only they were not +P which got the velocity under the speed of sound. Spied crunched in the bottom of a range bag, which is how this convo came up, was a box identical to the one described with the exception of a large SP in bold letters on the end flap and no +P, of course.
I do not know if this is the ammo in question, but it sounds like it. Way too coincidental. Sorry for the long winded answer, but I really enjoyed that time in my life, and that ammo!! Hopefully, you enjoyed reading it. Ah ANGLICO, how I miss thee...