for frame of reference, 1 block (10 px) equals 5.667 inches. the CS-RC, which is based off the XM8 whose carbine variant is 34 inches, is 6 blocks long, which equals 34 inches (5.667 x 6). I used this weapon to determine what one block is in terms of length. some values are estimations; this is because you can't have fractions of a block in this game, meaning no 5 px, 3.33, 2.5, etc blocks, which makes calculating exact length in terms of block count more difficult overall. for those, I had to visually take a guess as to what fractions to use for certain weapons.
here's the full list of weapons, from longest to shortest:
Spoiler: Show More
as you can see, the scaling and proportions seem pretty normal in comparison to typical gun lengths irl. there's some oddities ofc like some assault rifles being as short as SMGs, but this is a game with weird designs in the first place so that's to be expected. in this topic, I had calculated that the marine was at least 6.195 feet/1.88 meters tall, which translates to a height of about 6'2. weapons ranging from 8 inches to 4.25 feet seem reasonable and believable when characters are already above average height. the game doesn't show the scaling in a seemingly realistic or proportionate way, especially with character sizes, but the scaling itself seems to be correct, even if not presented in such a way. it just happens that the smallest unit of measurement (1 block or 10 px) happens to equal 5.667 inches; because of this, the game doesn't have room for precise measurements or any units of measurement smaller than that as anything below 1 block is impossible to achieve. as a result, characters end up seemingly short while weapons seem perfectly fine.
for weapon length calculations, i used the formula ((n * 10) / 1.76470588). the number 1.76470588 was found by dividing 60 by 34. n represents the block count while multiplying n by 10 gives the pixel count. fair warning though, don't assume these values to be correct or canon either. for all I know, the scaling in this game could be way different. these are simply what I had found via this method and it's possible this method is entirely wrong.