Desk Jockey asked,
would the recommended ammo be the same for both a 3.7" barrel and a 5" barrel?
No. The shorter barrels have trouble getting ammo up to speed when using regular pressure 230 gr ammo that is designed to get up to velocity with a 5" barrel. Since velocity is critical to expansion of the hollowpoint rounds and since expansion can be iffy in handgun ammo, this can be a bad thing. To compensate, the better way to go would be to use a lighter ammo in the 3.7" barrel. preacherman says he uses GS 185 gr. +P ammo. I prefer Speer Gold Dot 185s. Both seem to be good performers out of shorter barrels.
Note that one of the drawbacks of shorter barrels is the aspect that since .45 acp ammo is designed for 5" barrels and since many defensive rounds have some fairly impressive flash from 5" barrels, the flash out of a shorter barrel can be significantly brighter since more powder has the chance to burn outside the barrel.
M2 Carbine uses Aguila IQ ammo in his 3" derringer. The telephone book tests he show do look impressive, and they would be if you were fighting wet phonebooks. The issue here is that phonebooks are not a good substitute for the real thing (human body tissue) or ballistics gel. Gel tests show only about 4-6" of penetration and that is not very much considering ballistics gel tends to allow greater penetration than soft tissue. The reason for this is that the lightweight metal does fragment into 3-4 pieces, usually, and each takes its own course. When the parts come off, they lose the synergy that comes with keeping the roudn intact, hence loose energy. This is akin to race cars that are designed (in part) to break apart on crash impact, each piece coming off carries energy away from the main part of the car containing the driver. Part of the result is that the car then stops sooner.
silicon wolverine said,
If you ever need your pistol in a "live action" situation, your body will be pumping out enough adrenalin to suppress any noise above normal. Its one of those "involuntary" bodily functions that happens understress. Kinda like crapping your pants when you get hit by a train.
SW
No sir. That is very much in error. Adrenaline does not suppress sound or sight for that matter, although people may not hear the shots they are firing and may have tunnel vision. Shots not being heard is called audio exclusion. Basically, some or all sounds may be 'ignored' by the brain under stress. This does not, however, protect the ear from hearing damage. In regard to vision, tunnel vision may appear to reduce a person's sight, but the rods and cones in the eye can still be burned out if you stare at the sun if you have adrenaline tunnel vision.
In both cases, the damage is physical, not mental.