You can...if you look in gundata.ini
see this
you will see its sound ...GunFireSound=50cal
you can either copy the gun...and copy the ini entry...and create a new sound and add the new name..via the gun editor..
easy
[GunData001]
TypeName=30CAL_M2
FullName=0.30-cal M2 Machinegun
Caliber=7.620000
ROF=1200.000000
MuzzleVel=835.000000
AmmoWt=0.009730
WarheadWt=0.000000
Reliability=97.000000
Accuracy=70.000000
AddLight=FALSE
MaxLightRange=1000.000000
FireColor=0.150000,0.150000,0.150000
GunFireEffect=LmgFireEffect
GunFireSound=50cal
EffectClassName=LmgEffects
EffectTime=0.100000
TracerTexture=Tracer.tga
TracerSize=0.150000
TracerDistFactor=0.002000
TracerLength=0.015000
MaxVisibleDist=4000.000000
MaxStreakVisibleDist=1000.000000
TimeFuzed=FALSE
btw...you can do all the above with the gun editor...apart from making the new .wav file but thats easy too..