TM MP5 Ras Upgrades
 

After finding a crack in my mechbox i replaced it with a newer black version, and having a lack of 7mm metal busings its going to require another strip down..

While adding new bushings, im thinking of doing a few upgrades, right now it has the stock 230mm barrel. Im debating doing a tight bore 363m -400mm
If i do a 363-400mm tight bore should i do a bore up kit?
also what is the difference in a m4/m16 bore up kit or are they the same? (should all be v2 unless the port is difference? ) although im thinking non ported to accommodate the longer barrel and get a bit more umph out of it..

http://www.airsoftcanada.com/showthread.php?p=978493

Should have all the info you need for information on cylinder porting and barrel length.