yes the b2k3 and b2k3 are not very much different
the only big difference is the regulator
they made a new one for the b2k4
everyone said the b2k3 reg. was inconsistant so they just put a new one on the b2k4
but the b2k3's reg is not as bad as everyone says and u should be fine as long as u are shooting nitro.
and u will probly plan on upgrading ur gun so a new reg may be in the near future
go b2k3 and you will be fine
zeo