So Contreras' terminal mentions a number of battle rifles in use by the NCR, but there's no such thing in the game. He's also involved with the unique This Machine.
One day something clicked and i speculated that there was supposed to be a non-unique version of This Machine, which would have been the battle rifle.
Thoughts?

inb4 "useless thread"

Your right, though why M1 Garands would be used as battle rifles in the late 21st to late 23rd centuries is beyond me.

But it doesn't surprise you that hunting rifles, revolvers or lever guns would be used?

It's a post-apocalyptic world. Weapons are in short supply and anything that shoots will do. Garands are powerful and reliable rifles, and there are lots of them still around, in military surplus stocks and in the hands of collectors and hunters. It's quite reasonable that a Garand would surface in the Fallout world, or even that the design would be resurrected for production due to being cheap and simple compared to the more advanced designs.

(Just to give you an idea of how many M1 Garands are still around- in September South Korea sought to sell 850 000 Garands and 750 000 M1 carbines on the US civilian market because the Obama administration wouldn't let them).

M1 garand is a battle rifle whether people use it or not.

It would be my second choice rifle if i ever happened to get in to a nuclear wasteland, first being a Kalashnikov

I'd rather have an M-14 than either of those, but an M-1 was a devaststing weapon. People often complain about the lack of stopping power of the M-16 we use today, which uses 5.56mm ammo. No one complained about the M-1; its .30-06 rounds hit like a sledgehammer.

Truth be told, weapons tech hasn't advanced that much in the last 150 or so years.

The M-16 we use today is about 50 years old.
The AK-47 (the most prolific battle rifle in the world) is 63.
The M1911 .45 (which many of our Marines prefer to the M-9) is 100.
The 9mm Parabellum cartridge (still in use today by numerous armies) is 103.
The Winchester 94, the deer rifle of choice for many people, is over 110.
And the Lever action in general is over 140 (the Winchester "Yellow Boy" .44 came along in 1866).
Finally, the double-barreled shotgun still popular for home defense is over 150 years old. The pump action is well over 100. And the 12-gauge shotgun remains the manstopper by which all others are judged.

Because they are 9 pounds of concentrated Jesus, that's why.