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FPS Limits at fields with hop up on or off?

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Old July 28th, 2013, 12:27   #1
gilps03
 
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FPS Limits at fields with hop up on or off?

So when I have everything set perfect for how I am going to game my gun it shoots 391-393. When I turn the hop up all the way off it shoots 408-411. If the field limit is 400 max. Am I trying to pass a hot gun? I have no intention of firing the gun with the hop up all the way off. Who would?

Just want to be clear as I see many hosts state that they will be dialing hop up's back for the chrono tests.

Thanks.
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Old July 28th, 2013, 12:36   #2
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Hop up off universally is the only true measurement that is equal for everyone.

However, for airsoft guns, a gun shooting 410 fps with no hop would get 100 feet of range at best, but 390 with hop could get 250 feet of range.

Which is a better situation for controlling velocity in a manner consistant with safe play?
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Old July 28th, 2013, 12:40   #3
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The field limit is the FPS the gun shoots while playing: it would be pointless and utterly asinine to force players to "unset" hopup for chrony, specially considering how much time/effort goes into tuning hopup properly. I've never seen anyone do that.

10fps is pretty negligible and most places I play would allow it with a warning (YMMV).
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Old July 28th, 2013, 13:21   #4
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The field limit is the FPS the gun shoots while playing: it would be pointless and utterly asinine to force players to "unset" hopup for chrony, specially considering how much time/effort goes into tuning hopup properly. I've never seen anyone do that.

10fps is pretty negligible and most places I play would allow it with a warning (YMMV).
Yet, when you have a gun that shoots 340 fps with 0.30g BB yet will chrony 180 with 0.20g because of the excessive resistance the hopup presents, you are not getting anywhere near an accurate measure of the gun. In essence, the chrony is useless and a complete and utter waste of time.

I have argued for years that chrony is meaningless, it should be an energy measurement. Then, you leave the hopup were it is, you chrono with the BB weight you actually use and your energy is the limit, not the velocity.

ASC even has a nice colour chart for this purpose. I printed it off, laminated it and it goes everywhere my chrony does.
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Old July 28th, 2013, 14:27   #5
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Originally Posted by mcguyver View Post
Yet, when you have a gun that shoots 340 fps with 0.30g BB yet will chrony 180 with 0.20g because of the excessive resistance the hopup presents, you are not getting anywhere near an accurate measure of the gun. In essence, the chrony is useless and a complete and utter waste of time.
Dunno what setup would produce those results; I've played with .30 for years and have never witnessed anything even remotely like that.

I somewhat agree that a super strict chrony limit (max 400, 401 you're a no go) is pointless, moreso since FPS will vary slightly with altitude and weather conditions, and the energy being carried over range is different based on BB weights, etc. It does have value as a guide though: if someone is chronying 430 w/ .20s then there's a problem that needs to be looked at and I think that's the real purpose of it, not normalizing velocities across all players.
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Old July 28th, 2013, 14:37   #6
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Yeah, that seems a bit drastic.

Though I do agree that everything should be measured for muzzle energy with the weight of BB intended for use, especially with the amount of gas guns out there these days.
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Old July 31st, 2013, 15:09   #7
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I have argued for years that chrony is meaningless, it should be an energy measurement. Then, you leave the hopup were it is, you chrono with the BB weight you actually use and your energy is the limit, not the velocity.
BAM. this is where it's at. People should be chronoing with the weight they will be shooting and muzzle energy should be calculated from that.

It's WAY too easy to cheat a chrono if you know how the gearbox and air voluming works.

You could build a gearbox that would chrono 400fps with .2s which is 1.48J but with a .4 it might chrono something that's 1.7 or 1.8J... I pulled those numbers out of my ass, but it's possible to get higher J with heavier ammo with a setup that gets proper fps/J with a .2
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Old July 31st, 2013, 15:18   #8
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Its not really that easy to do with AEGs, any increases in energy from using a heavier BB would be minute, if existent at all.

With gas guns its extremely easy to do though.
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Old July 31st, 2013, 15:24   #9
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I agree it would be difficult to get anything significant from joule creep in an AEG, but it's still possible to get a benefit from it, even though a little.

I have read some technical threads on overvoluming AEGs to produce certain effects. Done right, it's not insignificant. but we're not talking a magical half a joule either.
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Old July 31st, 2013, 15:39   #10
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That is somewhat true when using a cylender much larger then the barrel volume. Once you swap to a heavier round it allows the cylender volume to be used more fully thus an increase in energy will likely happen.
Again tho itll be prety small. And also the J rating method can also be cheated by simply upping bb weight for game play.
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Old July 31st, 2013, 15:50   #11
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What it comes down to on average, is AEG's just don't fluctuate very much in terms of muzzle energy from heavy to light ammo.
GBBRs however, do. And by a lot.

So (at least in Mb), we've made it mandatory to chrono GBBRs with the weight they'll be using in field. From that it's naturally an easy step to do the same with AEGs.
On our chrono's we've got a list of what BB yields what fps at 1.6J, so we're always determining muzzle energy.


-you're definitely not playing with the hop OFF
-some guns, like bolt action rifles and GBBRs, actually GAIN fps by applying proper hop pressure
-some guns yield minimal fps with the hop off. Sometimes the air nozzle will push a BB past the hop rubber if it's off and it'll roll halfway down the barrel before it's fired
-some guns, AEG's included, can gain muzzle energy by switching to heavier rounds

So chrono with the hopup set properly, and ideally with the weight of ammo you'll be using in the field
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Old July 31st, 2013, 16:29   #12
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We bring two chronos to our games. One set to .25 and one to .28, which covers most of the ammo brought. The one with .25 has all the weights programmed in and can be changed quickly to any weight the player is using (from .20 up to .38).

This last weekend we had a couple of guys that where just over the 425 limit on one or two of the chrono shots (427 and 428) but under on a couple of others (420 and 421). No big deal.

We did turn away a gun the was running 525 FPS. Player had it fresh out of the box. He was told to go get a different gun to game (he had a couple) until he downgraded that one.
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Old July 31st, 2013, 16:40   #13
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We did turn away a gun the was running 525 FPS. Player had it fresh out of the box. He was told to go get a different gun to game (he had a couple) until he downgraded that one.
That's why people with couple of guns should buy a chrono... Even if they are not doing the gun doc work themselves.
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Old July 31st, 2013, 17:50   #14
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If you're not working on your guns....why would you need a chrono?
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Old July 31st, 2013, 18:13   #15
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I am going to come in and support Brad,

This type of example is very apparent with gas guns. Any of my gas guns chrono clean 420 w/0.2g, however when I shoot my "desired" weight .40g BB the velocity only drops to 350 ish. This is a HUGE increase in muzzle energy.

Another example. my AEG shoots consistently at around 420 w/0.2. It also shoots the very close to 420 with 0.32g

420 w/0.2g = 1.61j
350 w/0.4g = 2.24j
420 w0.32g = 2.58j

In both cases, after i walk past the chrono station, my muzzle energy has climbed ~38% or ~60% respectively. In the one case my AEG is over the equivalent 500 fps considered field safe.
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