If you don’t care about leveling up the rifle skill, Build a pneumatic weapon. Takes Mechanics and marksmen 2. I don’t remember what book they are in.
the Pneumatic Assault rifle 15/15 (dmg/range before ammo), or Pneumatic bolt driver (20/20 dmg/range before ammo). First one shoots marbles/pebbles, and the second one shoots crossbow bolts. They also use some of the rifle mods, so you can drop disperson, and recoil down a bunch too. Wooden bolts for the bolt driver. The metal bolts are HEAVY. This will do as much as a a pistol for dmg, about the same range.
You will then just shoot like mad, (and silent), for easily made ammo.
I personally like the bolt driver. Holds 8 in the chamber, and I like having the ammo in a quiver. Remember to mark them for auto pickup so you can be lazy.
If you don’t like those options get a nailgun. Hardware store, nails are easy to get early. If you want a ton, get a shovel, drop a house. Clean up.
I have a 10 markman skill, and a 3 rifle and I hit for about 25-40 on the normal Zed with the bolt driver. Crits in the 50-90 range.
I switched to it from a reflex bow, as I found the rifle I want to mod out once I can get more ammo. If I need to hit something heavy from farther out, I pull the heavy crossbow from under the seat of the Death Rider. (Same ammo, more range, double the dmg, the reloads just a pain)