ICS m4 R.A.S. having trouble shooting
 

Hi fellow airsofters, I just recently purchased a ics m4 R.A.S, wanting to use this gun for CQB, i changed the spring in the gear box be my self, but some problems started occurring after i done that, when i try to shoot it some times it wont even shoot bb's, when it does that the sound is also muffled, some times it shoots multiple bb's at once, very rarely does it actually shoot normaly, and sometimes when i shoot in semi it will shoot in full auto for a second. Any help would be greatly appreciated:hammer:.

Take it to someone who knows what they're doing.

Is this ics m4 brand new or used

it's brand new, but i probably messed something up.

i am actually taking it to the store where i bought it tomorrow, just wondering if i could fix it for a cheaper price.