Extra cylinder volume will give you better consistency with heavy BBs. Since you are going to build it under 400 fps and probably use only .30g bbs I think its not worth it. You are better off with standard v2 gearbox.

 

That is virtually the same question i asked myself recently. 400fps max at my usual field as well

I can't say for sure, however based on internet research there are two questions you need to ask.

1) do you believe a longer barrel is more accurate
general consensus was ~450mm was ideal however there are some posts on this site about joule creap that i believe suggest a shorter is better (not 100% sure on this idea)

2) do you believe a tight bore is better than 6.05 or a wide bore like orga
for a non HPA gun i thing the very wide bore are a no go, but the general consensus seemed to be that a slightly wider bore barrel was good at range while the tight bore was best for medium range shots

If you want a longer barrel or to run wide bore barrel and want the proper cylinder volume to barrel volume ratio it could be worth it.

see my post for a volume comparison
http://www.airsoftsniperforum.com/43-longrange-aegs/15411-sr25-vs-m4-m16-volume.html

I ended up getting the A&K sr25K from air rattle (best price with all time free shipping)
A&K SR-25K URX Full Metal Electric DMR Airsoft Rifle

i plan on running ~450mm 6.05 barrel

I will update once my build is complete

 

Good to see I'm not the only one who's unsure about this lol. About the barrel, I intend on going 6.03 mm so no widebore for me. Lenght wise I'm not too sure... going to have to look that up...

 

From what I've seen you should be fine on a conventional v2 with a type 0 cylinder if your barrel is shorter and you use lighter bbs. Basically summarising ish200's post V2.5 is for >.3g bbs with >450mm barrel (approximately).

http://www.airsoftsniperforum.com/showthread.php?t=15411

 

I might be an odd one out here, but I actually prefer 6.03 barrels in all of my aeg's. I've had problems running a 6.01 with a gun shooting a little bit too fast (~30 rps) I think vibrations started to do a number on my accuracy. Maybe I just had a bad 6.01 In general though, you should be fine with that 6.03

 

You are not an odd one lol, 6.01 barrels yield similar results to 6.03 barrels, they just tend to jam more.

 

I guess the other question you need to ask is what weight BB you plan to use because that too will affect the desired cylinder to barrel volume ration. In general what i have seen is some where between 1.7:1 to 3:1 cylinder:barrel ratios with most saying 2.3 or 2.5:1. The heavier the BB you plan to use I have seen more people recommend a higher ratio.

I plan on testing out some different weights in my new build but based on internet research .3 has been recommend the most for ~400fps guns

 

Well .3g bbs is what I was looking for. Would you happen to know the volume of both a v2 and v2.5 gearbox cylinder?

 

If your shooting 500+ fps and using ultra heavy weight ammo then yes, it's worth it. If you want to use a ultra wide bore, then yes its worth it (bore up cylinder in this case).

I'm going to skip the math and just tell you I've tested both 2.0 and 2.5 gearboxes at 500 fps and its just easier to do 500+ and use .43 with the 2.5. Just make sure you use a quality gearbox. CA at min, Retro Arms at max OR brace it with a well lock if using a cheeper A&K gearbox. This applies to springs m150 or above.

At 400 to 450, a standard gearbox is fine even in full 509mm barrel length.

 

V2: 72mm long cylinder

V2 extended: 82mm long cylinder

inner diameter should be roughly the same ~23.5mm

 

Inner diameter is usually 25.4.

 

My idea was to go with a krytac since the internals are so good ootb. I wouldn't need to change a thing except a new air nozzle maybe and some tweaks around the hop up.

 

i am not 100% sure but measured my CA sport line m15a4 and was ~23.5. Note i did this with a ruler so not perfect.

figured it was close enough based on this post
Pyramyd Airsoft Blog: Calculating the Optimal Inner Barrel Length for Your Upgraded AEG (Using a Classic Army CA25 AEG)

Zero: you talking about a bore up set?

 

For a v2.5, it should have more length and bigger diameter, so yes.

 

Damn its so hard to choose! I love the look of the sr25, but I like the Idea of an almost perfect krytac right from the start...