Quick Question (changed)

I have 2 simple questions I have no clue as to what the answer is.
1: What is the inner barrel length of this http://www.airsoftpost.com/product_info.php?cPath=25_86_267&products_id=28683 Also, would it fit on a combat machine m4 with no upgrades?

Sorry for double post, but for anyone who saw it, 1st question is changed and my second question was answered.

It should be the standard M16 barrel length...which is...509mm. I recommend using a 6.03 tbb.

Pending on what kind of frontset you have on your G&G, if it is free-float there should be no problem.

I have a normal combat machine nonblowback so would that work? Also, was planning on getting a Prommy 6.03, SCS nub and systema hopup. Since my gun is still front wired, I assume I could get the wires through this thing and put on a PEQ box, right?

It should work fine.
Yes, if you do not wire it to the back you will have to get a PEQ box. (i had the same problem recently)