I can tell you that there is a huge difference in sound between super and sub sonic 308 rounds.

I only use subs for fun, I've never shot an animal with one, but the 180gr soft point subs I use have a 8 mil drop at 200 yards compared to the 168gr AMax supers I shoot. That is a huge amount of drop. If you don't have a house within 500 yards of you I'd say you'd be fine unless you were for some reason aiming in the air LOL.

I use full velocity 22LR out of my SBR (10.5") and with suppressor you can not hear the full velocity at 100 yards. You'll be able to hear the sonic crack but don't think you neighbors will. My nephew was at the 100 yard berm and I was back at the platform and he was doing mag dumps with the 22 suppressed and I never heard the crack just little thuds of the the bullets hitting the berm.

A .177 Gamo hornet or any of the typical "1,000 fps" breakbarrel will kill armadillos. Just use well placed head shot at a flat angle to the skull. I have used a .25 cal break barrel that chronies 700 fps with 25.4 grain JSB pellets, and it kills armadillos with a single shot through the boiler room no problem.

Edit- if you are worried about pass through and ricochets, I think a .17 hmr would be ideal. It will fragment and probably won't pass through even up close.

12 gauge 3.5 inch (joking)

Well I've been busy all day and now have a long list of responses...almost none of them consistent with each other. Sounds like there's more than one way to skin a cat. I might start by trying to trap them. That would eliminate me having to shoot at night at all, and I could take him out back during the middle of the next day and wouldn't have to worry about ricochet either. And I wouldn't have to get up in the middle of the night to keep hunting them.

Sounds like rocochet is a mild concern even with subsonic ammo, and noise would only be significantly improved if I got a silencer, which is expensive.

I know the path they travel, so it shouldn't be too hard to set up a trap. Might not get all of them, but if I can start dwindling them down it would be a vast improvement. Might keep my pellet gun or 22 handy in case I get a point blank shot on one and I'll use the 12 gauge once they're trapped.

If you try this , be aware they jump straight up when startled .

10/22 with suppressor and sub sonic ammo, is great. My neighbor has been known to
let them dig almost out of sight , then stick a 12 ga down the hole. Then just covers them up.
Lets them dig their own grave .

MO

Ground must be a lot softer where you live!

I shoot them with a .22 mag. Never had a problem when using that.

I would get rid of the grubs in the yard.... get rid of the grubs and the armadillos will take care of themselves.

I like armadillos. I would let them stay.

You would be amazed how fast they can dig in a nice wet East Texas flowerbed.
A dog nipping at their butt makes them dig even faster

MO

They love St. Augustine but I have a 1/4 acre lot next to a rent house. There are many reasons my water bill is $200 and 'dillos eat here.....set myself apart with a nice yard usually. Neighbor across the street lives on top of their burrow. She has a hole in front of her house up under her foundation (slab mind you) where the damn mini-dinos live.

The things are famous for carrying leprosy. - I would avoid the bloodier methods, and wear gloves when handling the carcass, if I were you.

Caught one in a trap last night, but he got out. I didn't realize how strong they were. Actually bent the locking mechanism on the trap by pushing on the door. So I'm going to try reinforcing it tonight. But I'm now going to consider buying a more expensive trap that I know can handle them. Some of the good ones even come pre-scented. I really didn't want to spend $100, but I gotta get rid of these things.

Just get rid of the grubs in your yard. That'll fix the problem

I've got 1.5 acres. That sounds like a daunting task.

Yep that would be problematic

Not really. Powder Tide is all you need to use. Spread it out like a fertilizer. Kills the grubs and the armadillos stop coming into the yard. The Tide doesn't hurt the lawn as far as I know.

I use standard velocity .22 LR with either my rifle or pistol and a suppressor. You could be standing in my yard and not know I shot.
There are some live traps that work awesome. A friend uses the following one and it seems to work awesome for him and his neighbor. You have to get the scented trap.
http://thearmadillotrap.com/

Another guy I know put up a little 12" net diagonal across his side yard between the house and a rock wall and left opening at either end. On one end, he put a regular wire live trap. Armadillo will get funneled to the open end going one direction and then get funneled into the trap going the other direction. Simple idea and it works awesome. He just checks the trap every day and dispatches the armadillo with a .22.

I like the critters myself. Never shot one

I feel like trapping and killing the armadillos is better than putting out poison. I am not aware of the ecological impact of Tide, as far as I know there may be none known. But often, chemicals we think are harmless actually have an adverse impact on wildlife, and the tide may kill other more beneficial bugs. Armadillos on the other hand, dig burrows that are detrimental to the foundation of the home. Livestock break their legs in armadillo holes as well. They are not sought after for food, sport, or sale and their main predators are vehicles, so their numbers are only thinned out near roads. They may be cute, and it may make you feel good to give them a b.y.e. and go after the food source, but I feel like trapping and killing them is the more ethical and ecologically friendly path...

baseball bat works wonders bud... fun, HILARIOUS is you get it videoed, basically 0 ammo cost... and you get a free work out chasing them around