How do I make an AK 47 gun sound sound bigger like fired from a 50 caliber rifle?

What I currently do is use Audacity to apply some sound compressors and increase the bass a bit.

What more should I do for it to sound more convincing?

I don’t have access to 50 caliber machineguns or m4 Beowulf or a Barret 50 but a Barret might sound too loud for an assault rifle.

A little echo and delay might help “fatten” the sound further.

I think you’re fairly unlikely to encounter a critic who actually knows what a particular weapon sounds like such that (s)he would object to any nice, fat, loud sound.