This is pretty good, i like the entire style of it but i didn't really know if it would fit in-game so i tested it out myself. On the famas (didn't really have an M203, lol)

The greatest thing in my opinion about this sound is how you managed to get it so clear. There are no grains, no bad filters and the bass and amplification isn't overused or underused. The amounts of filters are just right and it has the right amount of echo and reverb.

The reload sounds are very realistic too it's just that they sound a bit generic and with the background and atmosphere in it, you can tell that it was recorded and as i said in the previous paragraph, it's clear which is very hard to do on a recording.

Now the problems on it, the reload sounds have echoes in them which makes them sound loud when their soft so remove the echo on them and paste it onto the main fire sound seeing as how grenades need a lot of echo which brings me to my second point. The fire sound lacks echo and reverb and it lacks a LOT. Take all the echo from the reloads and paste them onto the explosion (fire) sound and then amplify it a bit. The explosion sound seems a bit generic too imo. It also overuses bass alot so decrease the bass and amplify it for that unique effect.

Overall, good job on this. It's realistic and clear but a lot of things (listed above) were overused and some underused.

Just a side note : You should credit Valve because i recognize that explosion sound from Half-Life 2. I know it's been tweaked a lot but you should still credit them.