FPS vrs bb weight

[sp00n]

We all know that increasing bb weight reduces the bb's FPS, that's a fact.

however today i received my madbull chrono (not the most accurate but it gives me an idea etc), and decided to chono my mp5k and G18c AEP

my glock was coming in at 190'ish fps with 0.25 blasters, and 14bb/s on its lipo's

I had some old 0.2's in my mp5's mag, and i was only getting 170 - 190'ish results, after 3 or 4 shots the mag was out, so i refilled it with 0.25 blasters.

i was then getting 220 - 230'ish FPS ... a 30FPS increase when going up in bb weight!!!

(on auto i was getting 17 - 18 bb/s)

i am at a loss to explain how i gained FPS, it should be impossible .... then again the 0.2's were some old cheap ones .... they may have been fireball's i cannot remember.

anyone have any idea's???

 

[Ian_Gere]

If you haven't used it for a while, maybe it took a few shots to get the air seal working properly...?

 

[Airsoft-Ed]

Glitchy chrono.

Physics simply cannot be broken like that. Fire into the distance and see how the shots fly. That ought to clarify what's happening better. I can roughly gauge fps by eye I've switched it about on my L85 so much.

 

[sp00n]

If you haven't used it for a while, maybe it took a few shots to get the air seal working properly...?

Click to shrink...

i hadnt use my mp5 in a week, and then it had been cleaned and lub'ed.

Glitchy chrono.

Physics simply cannot be broken like that. Fire into the distance and see how the shots fly. That ought to clarify what's happening better. I can roughly gauge fps by eye I've switched it about on my L85 so much.

Click to shrink...

the chrono is brand new out of the box (so i would hope its ok), the only thing i could think off is that the 0.2 bb's are fireballs, and i am unsure of there quality .... if small air could be going round the bb???

i completely agree with you there Ed, physics cannot lie! .... this whole thing has left me puzzled ....

 

[Airsoft-Ed]

Some chronograph readers can glitch out, unless they're those epic £200+ ones. There are a few things that can make it read wrong - the angle you fire it though, whether it hits the edge or not, how close the back end of the chrono is to a back stop, how far the muzzle is from the front end.

Firing through at an angle shows a lower reading, hitting the edge can make it say anything, if you're holding the back end close to something to stop the BB, like a pillow or whatever, then the BB can bounce back in and screw up the reading. Lastly, if you have the muzzle too close, sometimes you get stupid readings of about 10fps... Maybe it can measure the residual air passing through...? I've no idea.

Did you try it consistently over 10 shots or more and see the same results throughout?

Did you alter the hop?

Have you tested it again since?

Only other thing I can think of is that you must have .30s when you think they're .20s, maybe they were bagged up wrong in the factory or something, 'cos otherwise it's just completely impossible...

Unless the BB diameter is wider than usual and they're scraping down the sides of the barrel or something, or thinner to the point where air escapes past the .20s significantly more than the .25s, to the point where the .25s are propelled more evenly, by more air, and end up having a higher reading... Though the amount higher that they read is ridiculous, 30fps is about the drop difference between a .2 and a .25 generally speaking.

You couldn't have just been having the most epic derp moment ever and got the BBs mixed up, could you? Lol.

 

[sp00n]

like i said my chrono isn't the best, its a bulldog, it is consistent though. I never touched the hop at all on my MP5K, and it is secure enough not to move.

i ran out of my original test 0.2g bb's (i only normally have 0.25 blasters, a unopened bag of 0.23 G&G bb's, and a pot of 0.4 black sniper bb's), which were fireball's, they bottle did say 0.2g but you are right they could have been anything.

i was firing as close as i could, the bb's didn't bounce off the side as far as i know, or i didn't feel anything if they did.

today i got a bag of some BB king 0.2g's bb's (i cannot justify wasting blasters when plinking), the results i got were all in the 240 range (238 - 245), much more consistent and more inline with what i should have seen in the first place. (using my TM MP5K, though i still think i am missing 100fps some where :angry: :angry: but i have no air leaks as far as i can tell)

i just tried some of the same ammo through my G&G raider (its hop is still set for 0.25 blasters), and got a consistent 320fps (with the odd 330), which is right where it should be (with zero hop, when new, it originally chrono'd at 350fps at a skirmish), testing with 0.25 blasters i got 275fps with the odd 313fps.

Interesting though, my G18c AEP chrono'd at 197fps with this 0.2 ammo, and 190fps with my 0.25 blasters, this may be because i have not set the hop yet.

Well thinking about it, you must be right Ed, as the only reasonable explanation is as a miss labelled bottle on the fireball's