I will not debate the effectiveness of the calibers of the M632 or M432 as they might be descent self defense calibers - I have never personally done the ballistic research on them. That said, they won't really do anything a 38 special or 9mm in the right configuration won't. 9mm and 38 special are comparatively inexpensive, available almost anywhere and quite effective in the right bullet brand & configuration. For the most part you would be looking at a semi auto in the 9mm chambering, but the guns that shoot them have come a long long way!! The large selection of Micro 9's are small, light, compact, hold 10-15 rounds and are flat easy carrying handguns. If you still favor revolvers, good ole' Chief's Special's (M60 / M36) are still available in dozen's of configurations and ammo is also readily available and effective.

These days, there is a serious push by our government to severely limit, restrict, and make ammo hard to get and expensive to purchase. The calibers that the guns you mentioned come in fall into an "odd caliber". By odd I mean it was introduced relatively recent and while some have purchased them they are not exactly what I'd call common enough to find an most stores that sell ammunition. If you do find it I would imagine that the variety is limited and the price is somewhat expensive compared to popular SD calibers. While a revolver chambered in a smaller caliber allows for a 6th round, like I mentioned above, if capacity is a concern, look into the Micro 9's. For those who can open up their mind to the new crop of SD pistols, they simply can't be beat! I was a die-hard M60 fan and carried a Chief's Spl. for 40+ years. The day I shot my friends Sig P365 was the day I changed my mind about SD guns. Try a few different brands and models as it might open up a whole new world for you. If you are still convinced you want to carry a wheel gun, a more commonly available caliber might be the way to go.