A friend has a horse boarding place in Fort Worth. 50 acres, so he can shoot a centerfire caliber. That said, noise is an issue, and he's highly unlikely to get a suppressor. He needs to occasionally shoot hogs, some in traps, some up to 150 yards. He can usually get closer. He has shot and hunted, but doesn't own a gun now. I was loaning him my Marlin .357, but his hand left it dirty in the case, and I'm fond of that gun. Thought he might get one of those, but that's a costly gun these days. Not sure if a 22 mag would do for him. What are your suggestions? I'm assuming he will want to keep the cost reasonably low, since he won't use it much.

marlin 30-30 lever action.

Does he need a scope or is he OK with irons? If he liked the Marlin .357, and he is OK with irons, have him look at the Rossi model 92 in .357. I have one and love it!

An AR 15 or if gonna go cheap as possible and even less noise, a savage A22 .22 mag.

When I first moved out on my own, i rented a trailer on the corner of some dudes horse pasture. He used a ruger mini 14 on coyotrs and pretty much did a mag dump on them every night. Horses didnt seem to mind!

The horses don't mind. The neighbors got concerned when I fired my AR. Might have been the multiple shots trying to hit runners, though.

Not sure if he needs a scope. I'll look into it. Think a 22 mag would do it for a guy who might not be the world's best shot?

I consider myself a pretty good shot, and I would use .22 mag if it were all that I had available, but I definitely would not choose a .22 mag if I had the choice. Especially if he is looking for a not so loud load. For reduced noise without a suppressor, I would look at a pistol caliber carbine, or maybe a 300blk in bolt action. You'll still get noise, but not as much as .223 or any of the faster centerfire rounds. Fast bullets that break the sound barrier can be pretty loud, even small calibers like .223. Heavy bullets in subsonic will be quieter even without a suppressor. If he loads, or is willing to contact Chad for ammo, just about any caliber in a heavy bullet with subs would do the trick.

Be careful that the bullets DO NOT CROSS PROPERTY LINES. Any centerfire or rim fire is going to have noise and more with rapid fire (follow up shots).
Trapping might be a better solution.

Definitely aware of that. The city does trap them, but some are trap shy. And at Christmas the city quit emptying the traps for two weeks. Shot those in the traps.