how to chrono a GBBR?
 

Hey I got a quick question.
When at a field and its time to chrono guns, how do you guys chrono in your GBBRs.

With a GBBR I have read alot of places that a heavier round can actually up the FPS if not keep it the same as the lighter round as its in the barrel longer to allow the gases to expand behind it. So do you use .20s? or do you use what you will be playing with.... or do you calculate in energy?

GBBR's are chronied the exact same as AEG's.

I am not sure how a heavier round can make the FPS go up though. that does not sound logical.

Chrono with 0.20's, same as AEG's.

But yes GBB's have a different effect when moving up in BB weight.
They retain more energy because of the gas expansion and having more time in the barrel to use that pressure.

For example when I had a KJW P229 (which has a really short barrel) it would chrony 270-280 with 0.20's and 260 with 0.28's.
If you did the same thing with an AEG it would go down about 60fps to 210-220 or so.

Fixed that for you to reduce confusion.

It's all due to the compressed gases expanding. heavier bb = more time in barrel (initially slower) for the gas to expand and fully release it's energy.

But yes, most fields measure it the exact same way as AEGs, though some host may do a joule calculation if they take the expansion effect on heavier bbs into account. Though I doubt, at least for M4 or shorter length barrels, it will have too drastic an effect, may be wrong on that though.

get a good chrono, it should be able to measure in joules, set it to what weight you want to fire, fire with the weight you're gonna be using and see what the Joule rating is.

yah I tried the tac shops out here. says my rifle is firing at 2.49J.... thats DMR/sniper territory. I measured with .25g and set it to .25g on the thingy....

So I guess its npas time eh? lol.

lol that's 518 FPS on a .20.. Unless your club's cool with that... Npas time!

The Gen2 Wetti M4's shot around 600fps out of the box... and (without knowing this at the time) we shot a buddy in the ass from 15 feet away with a .28.

It dented his jeans. :\

yah its about 460 fps on .25, 140m/s I think is what it said I can't remember. our sniper limit is 550fps so I do fit under the bar there. I have my mac11 for close range or my hi capa.

Still trying to figure out the stupid bolt lock issue.

Well although the theory behind heavier ammo = more joules works, and it does make a difference, the difference is like a mere 10 fps
I chrono'd a WE M16 on .20s and .30s, and the difference between the joules of force equated out to around 10fps on .20s
The biggest factor for GBBR is the heat, they shoot harder when they warm up