I have just recently picked up a Glock 42 .380 and would like thoughts on what preferred ammo might be for one of these. There's a lot to choose from and I have zero experience with this.

.380s ain't much, so I'd go with Underwood or Buffalo Bore ammo, and hope for the best.

For defense/serious stuff the Underwood +P load using the 90 gr XTP is where it’s at! Best combination of enough penetration and some reasonable expansion. Most JHP loads in 380 don’t penetrate sufficiently. For practice the Winchester White box JFP is fine. I handload myself and just about run the 90 gr XTP for everything.

A 90-100 gr cast flat point would be nice to have since it should get a little speed at safe pressure, but I’ve never gotten around to getting a mold cut for one.

Mark in GA

The Glock 42 comes with a stiff dual recoil spring assemby, and I would wring it out with full strength ammo to break it in. I've got two that have been shot a lot and are reliable. As far as ammo goes, it is hard to get both expansion and deep penetration in .380, so pick the one that is most important to you and go from there. The hollowpoints don't penetrate and don't do well against barriers, while the hard cast (NOT soft lead ammo) and solid copper rounds tend to penetrate well but barely expand.

I load 115 round nose cast and jacketed for mine.
The loading data is out there.
Its a humper for sure but pay VERY close attention to powder charge and seating depth and rock on.

I measure every powder charge and then seat a bullet.

I make up 50 at a time and use it at deer camp......my little glock 42 burps, farts and asks for more.

I have used it on trapped hogs and it works very well indeed.