Tight bore upgrade - 407mm on G&G SCAR-L

[Zack The Ripper]

So I have a question regarding barrel length in relation to cylinders. As the title suggests I have a G&G SCAR. I'm adding a tight bore barrel which is longer than the 300mm stock barrel as I have a suppressor/barrel extension. Now I have been told by some people that it can get tricky when going anywhere beyond 400mm in length as if your cylinder isn't big enough, you won't have enough compression space for the length of the barrel. I heard some talk saying you need a "full cylinder". Now I know some stuff about internals, enough to get by, but this is an area I'm clearly clueless on.

I have a 380mm TBB I ordered, but I have to option of changing that to a 407mm if I want, and I kinda want to. I'm just wondering what effects this may have as I'm not sure what kind of cylinder I have in my SCAR, nor do I have any idea if there was any fuckery in what I had heard regarding cylinder size. Basically I'm just trying to find out if the 407mm length TBB is a good choice for the SCAR.

Any info is appreciated.

Thanks!

Zack

[ThunderCactus]

What brand of barrel?
If it has the proper cyl for 300mm, it'll need a new cylinder if you go above 340ish
Between 380 and 407, no big difference

[KenTsui]

What FPS are you shooting and what weight BB?

You need to figure out the ratio between the air volume your cylinder can supply and the volume of the barrel in question. Typically, ratios are about 1.5 or higher (C:B). The heavier the BB, the higher the ratio should be to achieve better efficiency. Longer is not necessarily better. You might even be better off with stock length depending on your situation.

[Zack The Ripper]

My SCAR is hitting 360fps +/- 3fps with .20s. I normally use .25s or .28s. I may just stick with the 380mm if That's the case then, no sense going any longer if it will become less efficient.

[Hectic]

http://arniesairsoft.co.uk/?filnavn=...andbarrels.htm
This will show you what cylenders can use what barrels.
The higher of the lengths are the more efficient ones to use the shorter ones will have wasted air

[Zack The Ripper]

Sorry, just some clarification: you're saying shorter cylinders are more efficient for longer barrels, are are you saying the opposite?? Sorry, tired, long day..

[Hectic]

No im saying in the link i provided when it says s cylender is for xxx-xxx length barrel the longer barrel is making maximum use of the cylender and the shorter one is not so its less efficient.
So for a cylender with a 4/5 port a 460mm barrel uses all the volume and a 364 is wasting some (you will have lower fps and harder impact of piston to cylender head because the bb has exited the barrel befor the piston completes its cycle thus wasting air energy and lowering fps)
A vsr 10 is optimal for 500mm inne. A gspec has a 330 mm inner and with all the parts the same for a 500 fps build the 330 mm barrel will reduce fps by 100 as the inner barrel increases in length or the cylender port is moved forward (shortening the cylender) the fps increases
So if space allows in your gun (outer barrel length silencer ect) your beter to use closer to the maximum length that the cylender can support

[Zack The Ripper]

Ah I see. Unfortunately I have no clue what kind my SCAR uses.

[Hectic]

Just look at it and compare the port location to the ones in the pic. Itll most likely be a 3/4 or 4/5 (same as most m4's) lately ive found most of the m4 type rifles ive gotten use the 4/5 port i think the china brands just use that in most carbines and rifles

[KenTsui]

G&G SCAR AEG Dismantle Disassemble Airsoft Gun Rifle by AirSplat - YouTube

Look at 6:45. Looks like a full cylinder to me.