Chronos vs shot-to-shot consistency

[Gunboat Diplomat]

I recently picked up a cheap chrono from AliExpress so have been doing some testing to see how my Double Eagle fairs in terms of consistency, but I'm wondering what the benchmark is? 

 

I've done several runs of between 10 and 20 shots and nearly all are between 1-3FPS of one another, but then occasionally one shot may deviate by maybe 10-12FPS.  I'm not really sure here if that is an error in the chrono reading or a sporadic inconsistency in the gun.  

 

Here's an egregious example where one shot drops by 28fps, but the variance can be up or down and is usually less dramatic:

 

I had another example of a shot reading at 307fps, which for a .28g BB puts me well over the UK limit, but I'm struggling to see where it suddenly gained all that extra power from for a single shot.

 

For reference the gun has a Guarder 100 spring, ZCI hop unit, Macron 60 and Omega nub.

 

I'll frame this all by saying I don't really have any complaints about the gun in the field, this is all the the name of science/being a geek.

Edited June 30 by Gunboat Diplomat

[Cannonfodder]

If you're unsure whether it's the chrono then try borrowing one next time you're on site and doing the test again over lunchtime.

[Nick G]

307 fps on .28 is about 1.2j so still inside legal limit.

 

Sporadic air seal change is a possibility, a BB may be fractionally different in size for example , changing how it behaves in the hop rubber.

 

Are you holding the muzzle in exactly the same position relatice to the chrono every time ? I hind altering the angle or distance from the chrono can change readings some times.

[ak2m4]

You often get strange BB's acting different, it's not an accurate science as many variables.  I'm certainly in the "don't overthink it" camp. 

 

You're flying close to the sun there though.  A Guarder sp100 spring is roughly equivalent to a M110.  As @Cannonfodder says try another chrono and see.  You can spend ££ trying to eliminate the odd inconsistency however often better to just leave it alone and enjoy.

[Gunboat Diplomat]

33 minutes ago, ak2m4 said:

You often get strange BB's acting different, it's not an accurate science as many variables.  I'm certainly in the "don't overthink it" camp. 

 

You're flying close to the sun there though.  A Guarder sp100 spring is roughly equivalent to a M110.  As @Cannonfodder says try another chrono and see.  You can spend ££ trying to eliminate the odd inconsistency however often better to just leave it alone and enjoy.

Close to the sun indeed, didn’t realise at the time just how close to the limit the Guarder 100 would take me. I’ve kept the factory spring in my game day kit so I can do a quick change should I fail chrono. 
 

Oh I’ve no plans to try and chase any more consistency, it shoots fine irrespective of the numbers. This thread is really just for curiosity sake, the result of a quiet afternoon when I probably should have been fixing my garden fence but instead decided to play with my toys.

 

39 minutes ago, Nick G said:

Are you holding the muzzle in exactly the same position relatice to the chrono every time ? I hind altering the angle or distance from the chrono can change readings some times.

I am yes, as you say shifting the muzzle around can make quite a difference so for each group of shots I keep it pretty much static. 

[ak2m4]

yep Guarder certainly caught out a few people with their springs.  Funny enough when I initially started selling them I emailed the manufacturer many times asking if they could confirm what BB weight they rated their spring with, they said to me 0.2g which didn't make sense.   After coming across way too many stories of broken springs and people with the same issue as yourself I ended up getting my own springs made.

 

 

[Lozart]

Unfortunately, airsoft is an inexact beast at the best of times. Throw into the mix a chrono that is very possibly not terribly accurate or consistent in and of itself and you're on a hiding to nothing. Having been down the rabbit hole of diminishing returns myself, unless you're going to spend the money on a proper calibrated unit like a Skan or something similar then as long as your flyers are within the limits when tested on the site chrono, I'd take the win and leave it at that.