20 Inch Outer Barrel ? Inner Barrel

[Mad Dan]

Hello,

 

I'm new to the whole upgrade and extend thing but i figured i'd make a go of it and now i'm finding myself "stock blocked" and starting to question my numbers,

 

I have a fairly old Cyma CM.515 (M4) that's found itself being left behind, this was my first rifle and as such has two-tone polymer furniture but i wanted to give it some love and figured i'd replace these with fancy looking black alloys and maybe give it a custom paint job later down the line, at the same time I've decided i want to make her a little bit longer in the business end and settles on a 20in Barrel and 15in Freefloat handguard all looks good and i love it sofar, but now i've hit a little bit of a snag, all my early workings pointed me to needing a 509mm inner barrel (because for some reason Inner&outer barrels use different units) but now after spending a few months waiting for a  couple of 509s to drop into stock i've found another retailer who advertises "Upto 550" which has a nice gap between 455 and 550, no 509's.

 

Now this is where I'm stuck, i'd like the Inner barrel to sit flush with the CCW Thread and upon reflection i fear i may not have taken the hop connection into account and as such don't want to keep looking for a 509 to find its too short, or like wise jump on the 550 in stock to find its exactly as i expect it and be too long,

 

Can anybody please either confirm or debunk the numbers for me?

 

Thank you in advance,

 

~Mad Dan

[Adolf Hamster]

easy: go for shorter.

 

will make voluming a lot easier and in terms of accuracy there's not really much detriment to it.

[Cr0-Magnon]

Prometheus 509mm's are in stock here:

 

https://www.landwarriorairsoft.com/parts-c8/barrels-c103/prometheus-eg-6-03mm-stainless-steel-barrel-509mm-m16a1-a2-vn-steyr-aug-p8906

 

 

[Mad Dan]

Cheers Both,

 

Got this sorted now with a 509mm in, not quite as long as i'd hoped but it does the job well enough and the next longest is too long,

 

the reasoning for the longer barrel was/is more for Aesthetics rather than functionallity

 

 

Thanks,

~Mad Dan