Apples and Kumquats

Which handgun round is comparable to a 12 gauge shell?

Hey, I worked at a local swat like team in here and I carry a Remington marine magnum 6shell stack loaded and pistol grip shot gun as a primary gun. My commander once told me to use a HKUSP as a secondary pistol and told its good but when it nearly killed me when I needed more than five shots into the torso of my slightly armored shooter that shot me once and I shot him eight or so since I was nervous and clearly my commander had rather failed to protect me. Any ways do any of you know about a pistol or a handgun round that can do the same as my Remington marine magnum tactical shot gun and which gun would shot it the best. Particularly I say it should be able to kill a those type 1, 2 and 3 armored targets in one shot in almost all directions, carry a decent amount of ammo per clip although those twenty round pistols that need not even kill three from the whole clip are useless larger capacity would mean I could use it as a primary gun as well as a secondary and it should not give high recoil case the shot I took is for my right arm. It is very important for me to know it and you can answer by emailing me or at yahoo answering buttons. Give all sources.

No.....Really.....It was a actual question.