how do i make my gun not as loud

yea so i got a echo1 vector arms mp5 a4 and its really loud anyone know how i can make it not as loud

Foam. Pick up some foam sealer and fill in all the empty spaces in the stock and body.

proper shim job, AoE using a felt tip door stopper, non ported cylinder, and enough white lithium lube should get you pretty quiet when it comes to internals.

Some gearboxes you can seal in a foam case...especially bull-pups. But anything like a V2, V3 you can't because you have the selector assemblies in the way.

Just seal all openings on the gun body excluding cosmetic openings in the RIS, or free floating system. Focus on openings on the receiver alone.