How do you correctly check the FPS of a gun?

[Snakeeyes75]

Mornin' Sounds like a silly question but I'm just about to buy my first chrono (Xcortech), I chronoed my rifle on Sunday on site and it was reading 440 using .2's, now I had been told that it was chroned at 490. Only thing I can think of is, does the hop make much difference? I've set it to lift a .43 so can it slow the BB to the extent that a .2 will read 50fps lower? are you suppose to turn the hop off before testing?

 

[n1ckh]

The hop will reduce FPS but not by much, sounds like you may need to downgrade the spring, I had to do it in my JG g36c down to an M90 spring as to hot and my M4 as upgraded internals

What rifle is it ??

 

[Sitting Duck]

The max fps of a gun will or should be with hop off

However the norm is to chrono with hop set & shooting correctly

(else it would be right bollock-ache to mess ya hop up to chrono then pi$$ ball about getting it back fine tuned etc...)

Big long line of peeps tweaking their guns in the morning I guess

Some people may try to cheat chrono a bit on a slightly warm gun by giving it a bit more - thus excess spin will reduce fps

My own site suggested (off record) if I could get a 355 down a touch by adjusting chrono to 349/350

basically marshal could not allow a gun over 350 to pass chrono - just doing his job to the letter and I respect that

Chrono stats are done on 0.20's as the standard for site rules to ensure we all use guns within the sites own safe limits

So yeah - chrono with ya gun shooting correctly like what takes place at ya site

490 it might hitwith hop off, but travel much less, might not even get past 30m MED before it hits the ground

so no way would ya hit anybody with ya sniper in that case

Good chrono - I have the 3200 btw

Reckon you may be putting a load more spin on a heavier BB then when chrono on .20's the excess spin might

just might be giving ya lower figure - sounds reasonable I guess

But - the .43 Vs .20 is a lot heavier/lighter - wow quite a difference so would of thought the .20 even with a bit extra spin

should come out like a bat of hell

(Gone Gone Gone - soz couldn't resist that bit)

Dunno - sounds right but then it don't when you look at the weight or mass difference that a .20 comes out slower

HOW BLOODY LONG IS THAT BARREL OF YOURS - a metre or so ??

(0.20 bb must have gone upwards like a Harrier or Helicopter when it exited barrel with all that hop)

The most important thing is for sniper to understand MED whatever bb's they use

You are using one heavy mofo bb btw so that is why mental hop & strange difference I'm guessing

490 for a sniper may still be within limits (up to 500 aprox if site agrees or 450 if they don't feel happy with you sniping)

but over for a DMR (425 usually)

The figures are a rough guide only as all site limits vary

 

[Snakeeyes75]

The max fps of a gun will or should be with hop off

However the norm is to chrono with hop set & shooting correctly

(else it would be right bollock-ache to mess ya hop up to chrono then pi$$ ball about getting it back fine tuned etc...)

Big long line of peeps tweaking their guns in the morning I guess

Some people may try to cheat chrono a bit on a slightly warm gun by giving it a bit more - thus excess spin will reduce fps

My own site suggested (off record) if I could get a 355 down a touch by adjusting chrono to 349/350

basically marshal could not allow a gun over 350 to pass chrono - just doing his job to the letter and I respect that

Chrono stats are done on 0.20's as the standard for site rules to ensure we all use guns within the sites own safe limits

So yeah - chrono with ya gun shooting correctly like what takes place at ya site

490 it might hitwith hop off, but travel much less, might not even get past 30m MED before it hits the ground

so no way would ya hit anybody with ya sniper in that case

Good chrono - I have the 3200 btw

Cheers, yeah with the hop off the BB's drop at just over 30m, hop on then you're adding 70+ meters to that! I just had this nasty thought that I might have been given me an M130 spring rather than a M150.

I had a Mad dog a while ago and I just couldn't trust the readout, I've heard there's copies of the Xcortech, how do I know the difference? It's was listed as genuine from a UK source at £65 is this ok?

 

[Sitting Duck]

clones don't have shot memory

helmetworld I got mine from a while back

very very close if not exact same readings as my site's old 3200 chrono

(they used to have 3200 but lost the adapter/funnel so big fatty suppressors couldn't get aligned easily so they bought another make)

the shop - helmetworld is way overpriced - ffs, plus a discount code I had no longers works

the guy on ebay - if ya worried ask him to confirm shot memory blah blah blah

I got mine on helmetworld via ebay for £60ish ooooh 10months or so ago

 

[PT247]

Aye, with the hop wound off your fps will be higher, and it will make a big difference especially when using BBs over double the weight of the chrono BBs on site. A shop will chrono all their guns (I'd hope) in a consistent way, the only way to do that imo is to wind the hop off completetly, it will also make a guns spec sheet seem more impressive if out the box it is doing 500fps. As has been said you should chrono your gun on site with the hop set for the BBs you are going to skirmish, not for the BBs they provide. This will mean that your gun on the field will be as chronoed give or take 5 fps ish.

In the past I have chopped springs due to out the box fps being hot, when I've then taken the gun to skirmish and dialed the hop in my fps was closer to 300 than the 350 limit at Holmbush!

 

[Undieing_Lust]

Thats one thing they did at greenzone which always annoyed me was they turned your hop off after you had it set...

 

[BrightCandle]

I have always set my gun to work with the hop off, mainly because I don't have the space to get the hop dialed in where I work on the gun. But chances are I am leaving a good 20 fps off the possibilities with doing this because the hop certainly reduces the speed of the projectiles. But usually when I go to a site I am there with hop off, chrono and then dial my hop in. I guess I could do it the other way and creep my speed up a little but its just not worth it, especially since my gun has a slow tendency to undo its hop which would likely result in it being hot sometimes until I fixed it. That would not be good.

I don't know if its really 50 fps but that could very well be the case. You could chrono with 0.43g BBs instead and then just use the energy level, which is what everyone ought to be doing anyway since 500 fps with 0.2g BBs isn't really what its about, its about energy levels, which is 2.32J. Your chrono will allow you to set weights and see the energy level but if it doesn't go all the way up to 0.43g then you just need to know its 341 fps with a 0.43g BB for 500 fps with 0.2.

 

[Snakeeyes75]

Thanks for the replies! I've spoken to Sam at ASPUK, he's sending me out a new spring just incase, I'll be chronoing it myself in a day or so, it might have been a combination of the B type hop lever being set to lift a .43 and it was pretty cold when tested (Plus it was my first shot of the day).

 

[jcheeseright]

cold and first shot won't have made any difference, more likely to be the hop.

 

[Sitting Duck]

M130 is usually ya DMR type spring (425 aprox)

M150 should put you at 490/500-ish

this is on 0.2's shooting correctly but still a rough guide

but ya mofo 0.43's certain must be going some on hop to lift that fatty bb

so that is where ya 0.2 is way lower on .43 hop setting I reckon

ya own chrono comes in very handy when messing/upgrading/servicing ya guns though

 

[Snakeeyes75]

It has a M150 spring in it, with the B type lever I only need it 4 clicks back. (It'd be fun to see what trajectory a .2 would take with full hop on lol)