So you want to replace the M4 metal body because the dust cover on yout current one don't close properly? Isn't that a little... extreme?
Replacing M4 metal body involves a lot of adjustment work and the metal bodies can be expensive, so that's typically only done when very necessary. Probably you should try fix the problem on the current body set before considering replacment.
Some informaton for your gun and maybe picture on your current dust cover / ejection port may help.
Last edited by ccyg8774; May 1st, 2015 at 10:36..