Egon_247 Posted July 9 Share Posted July 9 So, i fitted one of Ak2m4's super-duper barrels to my boys mp5 a few weeks ago and then chrono'd it using my little silver chrono. Was showing 1j there or thereabouts. cool. we get to site on saturday and go through chrono and the guy tells me its lobbing 0.28's at 0.65j. Nothing has changed on the pew after my testing, even used the same housebrick of a battery. Now either mine is off or theirs is off as you cant just lose 0.35j in the space of a few days, can you? Is there a way of checking them (without another chrono next to it, that might be a bit more of a challenge to check!) It was shooting fine, range was 50m+ and other than changing out a poor feeding mag, had no issues at all. weird. Link to comment Share on other sites More sharing options...
Skara Posted July 9 Share Posted July 9 Did you chrono on 0.28s at home? Some guns do lose an awful lot of energy by switching to heavier BBs Airpig41, Rogerborg and Egon_247 3 Link to comment Share on other sites More sharing options...
Sewdhull Posted July 9 Share Posted July 9 Yours might be off a bit, theirs might be off a bit, temperature changes things. Stuff can happen do a gun, if you drop t maybe or stuff like that. Did you chrono it again at home? Egon_247 1 Link to comment Share on other sites More sharing options...
Egon_247 Posted July 9 Author Share Posted July 9 18 minutes ago, Skara said: Did you chrono on 0.28s at home? Some guns do lose an awful lot of energy by switching to heavier BBs Yeah, all my RIF's are running on 0.28's so it was good to go. 13 minutes ago, Sewdhull said: Yours might be off a bit, theirs might be off a bit, temperature changes things. Stuff can happen do a gun, if you drop t maybe or stuff like that. Did you chrono it again at home? Strange, Yeah, its chrono'ing at 1j again at home. Maybe time to upgrade the chrono, i've had it a while now. Meh, more moneys.. Link to comment Share on other sites More sharing options...
Tommikka Posted July 9 Share Posted July 9 There are many factors Try two chronos against each other for multiple shots The angle and proximity of a chronograph can get different results If you’re using a gas based system then changes can occur with ambient temperature and also the rate of fire / length of refresh time between shots Different types of chrono can get different results, even two of the same type/model may show a different result Chronographs try to measure the velocity of distance vs time, and where applicable Airsoft chronographs add the extra step of converting velocity to energy based on the entered weight / mass Egon_247 1 Link to comment Share on other sites More sharing options...
Egon_247 Posted July 9 Author Share Posted July 9 Its an older G+G mp5 AEG. Yeah, i've seen the gbb pistols i have cause havoc with the chrono. too close and its snorting gas, giving all sorts of weirdness off. I shall endeavour to find a new one and test them back to back, i think. Tommikka 1 Link to comment Share on other sites More sharing options...
Skara Posted July 9 Share Posted July 9 5 minutes ago, Egon_247 said: I shall endeavour to find a new one and test them back to back, i think. Find one that isn't yours nor the site's, you'll have a pretty good measure of which one is busted. If you're in the market for a new one, then you may look at the Acetech 5000, it's essentially the good ol' Xcortech mk3200 but in a different casing and with a few more functions. Egon_247 and Tommikka 2 Link to comment Share on other sites More sharing options...
Supporters Rogerborg Posted July 9 Supporters Share Posted July 9 This is why I take my chrono to site to compare it to the site readings. Hudson, Egon_247, ak2m4 and 1 other 4 Link to comment Share on other sites More sharing options...
Shamal Posted July 9 Share Posted July 9 It's the same with blood pressure machines. Tried three different BP units at hospital and all three gave different readings and my home BP unit gave another result. The hosp just took an average of the three. Hope that helps....NO! Egon_247 1 Link to comment Share on other sites More sharing options...
The_Lord_Poncho Posted July 9 Share Posted July 9 I've had the same. In my case, it was midcap syndrome - i.e. i was just adding a few BBs into my mag for testing at home (lightly tensioned spring, no midcap syndrome), but loading the full mag up on the game day prior to chrono resulted in the FPS drop on the first few fired through the chrono from the highly tensioned spring in the mag. Egon_247 and Rogerborg 2 Link to comment Share on other sites More sharing options...
Supporters Lozart Posted July 11 Supporters Share Posted July 11 On 09/07/2024 at 18:16, Shamal said: It's the same with blood pressure machines. Tried three different BP units at hospital and all three gave different readings and my home BP unit gave another result. The hosp just took an average of the three. Hope that helps....NO! I was concerned that I might have the same issue until I had my BP checked at the docs and they used the EXACT SAME machine I have at home. So that's nice. Shamal and Egon_247 2 Link to comment Share on other sites More sharing options...
NateChrony Posted July 13 Share Posted July 13 (full disclosure - I make chronographs) 0.66J vs 1J with 0.28gram is 225fps vs 277fps That's a huge amount of difference in terms of timing. Most of the manufacturing tolerances & timing uncertainty in designs is typically ~10-15fps when shooting 1000fps, with sensor spacing of 50-100mm or so. 50fps at that slow speed is something outside of a chrony's usual issues If it was gas - that could definitely cause an issue, anything that is a liquid & expanding can leave a vapour cloud & cause issues with optical sensors - typically you get high readings as the vapour can move faster than the BB. I'd say the chrony has a fault, take it to the field with you next time & compare side by side to rule out the conditions on the day. You could also possibly open it up & see if you can clean the sensors - cue tip & alcohol should be enough. Tommikka, Rogerborg, Lozart and 1 other 1 2 1 Link to comment Share on other sites More sharing options...
Supporters Lozart Posted July 15 Supporters Share Posted July 15 On 13/07/2024 at 09:22, NateChrony said: (full disclosure - I make chronographs) 0.66J vs 1J with 0.28gram is 225fps vs 277fps That's a huge amount of difference in terms of timing. Most of the manufacturing tolerances & timing uncertainty in designs is typically ~10-15fps when shooting 1000fps, with sensor spacing of 50-100mm or so. 50fps at that slow speed is something outside of a chrony's usual issues If it was gas - that could definitely cause an issue, anything that is a liquid & expanding can leave a vapour cloud & cause issues with optical sensors - typically you get high readings as the vapour can move faster than the BB. I'd say the chrony has a fault, take it to the field with you next time & compare side by side to rule out the conditions on the day. You could also possibly open it up & see if you can clean the sensors - cue tip & alcohol should be enough. Presumably, even at airsoft speeds, the further apart the sensors are, the more accurate the readings are likely to be? Link to comment Share on other sites More sharing options...
Skara Posted July 15 Share Posted July 15 7 minutes ago, Lozart said: Presumably, even at airsoft speeds, the further apart the sensors are, the more accurate the readings are likely to be? Given a constant velocity, yes. To have a 100% honest reading though, I guess the chrono needs to be setup in a way that the end of the barrel sits in the same exact position every time, relative to the first sensor and then needs to take into account the reduction in velocity given by drag, measured (or calculated) for each bb weight, in relation to the distance between the two sensors. And then everything needs to be certified somehow so that the readings can be used, should the need arise, in legal matters.... Something nobody hopes to resort to. Lozart 1 Link to comment Share on other sites More sharing options...
Sewdhull Posted July 15 Share Posted July 15 You'd want the sensors close to each other i think, so the measurement is less an average and more a snapshot. Timing can be done accurately over short periods and since you're matching the speed of light with a bbs doing 500fps I don't think you want the sensors far apart. The further apart the sensors are the more the averaging effect of the distance between measurement and the less you will see any differences in speed as they are lost to averaging. Link to comment Share on other sites More sharing options...
NateChrony Posted July 16 Share Posted July 16 23 hours ago, Lozart said: Presumably, even at airsoft speeds, the further apart the sensors are, the more accurate the readings are likely to be? yeah to a point (as others have noted) - as the wider apart you have them, the more the pellet/BB may be slowing down between them. This could be even more pronounced with airsoft BBs - the BC may be very different. Looking at rough size/spacing of common chronographs: At Airsoft speeds (250fps) - its a pretty trivial task on the electronics, you're talking ~500+ microseconds between sensors. 1 microsecond at 1000fps is the difference between 1000fps & 1008fps 1 microsecond at 250fps is about 1/2fps difference Another way of of looking at it is tolerance of assembly/dimensions: @200fps - 0.1mm = 0.2fps @1000fps - 0.1mm = 1.25fps The mounting is probably the most critical - i'm constantly amazed at how much vibrations & slight wobble have on the readings. But this is when I calibrate at 1,000fps - expect something like a 5fps variance if there's bad mounting, thats why I chose muzzle mount. Lozart, ak2m4, Egon_247 and 1 other 2 1 1 Link to comment Share on other sites More sharing options...
Egon_247 Posted July 22 Author Share Posted July 22 Sooo..... Tiny update as I hate threads that just die with no resolution... Went again to our site and had a great day. His mp5 was chrono'd at 0.7j on .28's. checked mine against theirs and was pretty much bob on. Cool. I used my G3 which was embarrassing and generally poo, but that's another story. Through the day he lost power and eventually used the back up DE badger. Yesterday I stripped it out and then realised that it was a "toptec" with the air cylinder blow back thing. So I swapped cylinders so no more blowback and on the SAME SPRING, chrono'd at 1.4j!!!! One point four. That's nuts. Also a tad illegal but I'm redoing the spring today. So remember kids: keep it simple. Blowback stuff on toptec is poo. Lol 😂 Rogerborg and ak2m4 1 1 Link to comment Share on other sites More sharing options...
Skara Posted July 22 Share Posted July 22 9 minutes ago, Egon_247 said: "toptec" Ah yes, that genius idea from G&G to create a huge air leak to move a completely unrealistic and unnecessary part Good riddance. Rogerborg and Egon_247 1 1 Link to comment Share on other sites More sharing options...
Supporters Lozart Posted July 22 Supporters Share Posted July 22 5 hours ago, Egon_247 said: Yesterday I stripped it out and then realised that it was a "toptec" with the air cylinder blow back thing. 5 hours ago, Skara said: Ah yes, that genius idea from G&G to create a huge air leak to move a completely unrealistic and unnecessary part Good riddance. TopTech isn't the name for the flappy horrible pneumatic blowback. It's just the range of guns that had an MP5 with it on. But yes, good riddance. Stupid idea. Egon_247 1 Link to comment Share on other sites More sharing options...
Egon_247 Posted July 22 Author Share Posted July 22 Shootin' a healthy 1.05j consistent now with added MOSFET goodness with a three round auto. Just occasionally I get it right 😂😂 Lozart 1 Link to comment Share on other sites More sharing options...
Skara Posted July 22 Share Posted July 22 3 hours ago, Lozart said: TopTech isn't the name for the flappy horrible pneumatic blowback. It's just the range of guns that had an MP5 with it on. My bad. I've always associated the name with the horribad system. In any case it's an ancient name I haven't heard in literal years, back then they were "the poop" alongside Classic Army funny to see how well the whole thing turned out Egon_247 and Lozart 2 Link to comment Share on other sites More sharing options...
Sewdhull Posted July 24 Share Posted July 24 On 22/07/2024 at 17:50, Egon_247 said: Shootin' a healthy 1.05j consistent now with added MOSFET goodness with a three round auto. Just occasionally I get it right 😂😂 Excellent, what MOSFET are you using? Link to comment Share on other sites More sharing options...
Egon_247 Posted July 29 Author Share Posted July 29 On 24/07/2024 at 18:11, Sewdhull said: Excellent, what MOSFET are you using? I believe it's a gate merf 3.2. I need to go through the settings and make sure the active brake is off as the grip seems to get hot quite quick. 👍 ak2m4 1 Link to comment Share on other sites More sharing options...
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