Good point, and I already have a .357 revolver for home defense (but not a closet of ammo for it.)
How has 9mm ammo been running cost-wise vs. 357 and 38 special, over the last year? (I'm not sure how valid a spot check right now is, what the trends are...)
If you already have a .38/.357 revolver, it’s about the same size as a 9mm.
https://www.metric-conversions.org/length/inches-to-millimeters.htm
Ya might as well stick with what you already have, get a laser sight for the revolver or keep to .38/.380/.357 and go with the carbine rifle so you don’t ever have to worry about stocking different ammo, you already have it and are used to it.
Ammo is coming down. The cheapest I have found is Walmart. All of my go to online dealers are still a bit high. Every time my wife drags me in to one I check to see what they have. I got a box of 30-06 (20 rds) and box of 330 .22s for under $40 about 9 months ago. The problem is they rarely have anything. Last time I checked the only thing they had was .350. I passed as don’t have anything in that caliber or know any one that does.
“I already have a .357 revolver for home defense”
Just be sure you have something else to shoot at night. The muzzle flash from a .357 will blind you for a minute or more and leave you unable to defend yourself or your family.....
I buy 9mm brass case FMJ in bulk for 30 to 35 cents a round. You're likely not going to find that price for 223, 357, or 38 special.
My observations based on 500 rounds bulk ammo. Prices are .,... ish,
9 mm - .32 per round
.38 special - .37 per round
.357 mag - .60 per round
So right now, 9 mm is cheaper brand new. Prices shift +/- 10% on a regular basis and often there are wild swings in price.
Also, I reload and find .38 and or .357 magnum cases easier to obtain and reload from my range. Yes there is a larger volume of 9 mm but a lot of the brass is NOT reload capable.
(torn necking, bent, etc)
Full disclosure, 9 is my general carry gun. .357 is my going to bad part of town gun. Trying to talk the wife into a .357 lever gun :-)