If the Classic Army M4 is a sportline (ie, costs less than 400 bucks), I don't recommend any of the four guns you listed.
I get that they're cheaper, but remember that you get what you pay for. They're not as well built, internals are prone to breakage, and in general will require a lot more work/money before they can be reliable
H&K G36c (KWA) / Glock 18c (TM) / Kimber LAPD SWAT Custom (TM) / Mossberg M500 (ACM)
Last edited by ap27; July 16th, 2012 at 20:16..