ICS M4 Inner Barrel Upgrade Compression Query

[cpldave]

Hi All,

I was just wondering if the stock M4 ported cylinder that came with my ICS M4 will cope with a 455mm inner barrel, or whether I will need to use a full-cylinder. It's currently 308fps on the dot and I expect to lose some FPS when increasing the barrel while keeping the stock cylinder, but there would be no point if it does something silly like drop to 208fps :P

My main point of concern is that I went from a standard M4 length barrel in my 416 to a 509mm and that did require a full-cylinder in order to maintain the correct volume ration between cylinder/barrel. I've seen lots of generalisations saying that up-to 455mm on an M4 ported cylinder is OK. Just wanted to see if anyone can confirm.

Any advice is appreciated.

Cpl Dave.