New to me (see box labels). Tried it out in the Tisas 1911 and P365, one mag of each. Cycles normally, goes bang. Recoil was not noticeably heavier than any other ammo for these guns. I think the 9mm case might be a tiny bid fatter than my usual Hornady. Could only stuff 11 rounds in the Sig 12rnd mag.
GunnyGene, as for the Underwood .45 ACP, this is a relatively slow round, and it generates only 484 ft. lbs. of ME, which is just a bit hotter than the average .45 ACP around which has 424 ft. lbs of ME. But I suspect that most semi-auto pistols cannot handle high powered ammo too well in the first place, so this one you picture here is of relatively near 'average' power, even thou it is from a normally high powered ammo manufacturer. I shoot the very high power Atomic .45 ACP ammo (Atomic) that delivers 616 ft. lbs. of ME, but I shoot this in my Ruger .45 convertible revolver, and there isonly a little kicjk to it from my big revolver. I can even shoot the .45 Super ammo, which can go up to about 700 ft. lbs., and with not including the very small 68 gr ammo by Magesafe, which I do not hink is manufactured any longer, that delivered 771 ft. lbs.! Underwood does make a high powered .45 ACP round, and it is a 185gr bullet, that travels at 1,200 fps, which delivers 591 ft. lbs. I have not shot the Underwood high powered .45 ACP yet.
