Hey there!
Recently, I found out that some guns could do damage to walls, and some couldn't. I searched online, but I found nothing. So I decided to test all guns in a singleplayer world, and came up with this list and the idea to make a guide of it. I hope the info in this guide is useful for you.

To spawn a gun using cheats, use the following command:
@give PLAYERNAME/ITEM ID

On a lot of servers, you can buy a gun by using:
/buy ITEM ID

Click here to view my other guide, containing all vehicle IDs in the game!

These are the guns that can do damage to bases, along with their Item IDs:

018 - Timberwolf

How much damage one shot does to a pine wall: 11%

126 - Nykorev

How much damage one shot does to a pine wall: 3%

132 - Dragonfang

How much damage one shot does to a pine wall: 3%

297 - Grizzly

How much damage one shot does to a pine wall: 11%

300 - Shadowstalker

How much damage one shot does to a pine wall: 21%

519 - Rocket Launcher

How much damage one shot does to a pine wall: 100% (Maybe even more, at least it will kill the wall)

1000 - Matamorez

How much damage one shot does to a pine wall: 7%

1364 - Hell’s Fury

How much damage one shot does to a pine wall: 2%

1382 - Ekho

How much damage one shot does to a pine wall: 9%

1441 - Shadowstalker Mk. II

(Only obtainable by using cheats or by completing the Mk. II Puzzle[unturned.wikia.com])
How much damage one shot does to a pine wall: 15%

If you see this icon, it means you're doing damage to the base.
If you aren't seeing it, check if you are using one of the guns in this list. If the gun is not in the list, stop shooting as you'll only be wasting ammo.

Thank you for reading!
It might be useful to bookmark this guide, so you can view this list quickly when in-game, you can do that by adding this guide to your favorites.