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Does "as heavy as you can hop" always apply?

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9.3K views 25 replies 13 participants last post by  philbegas  
#1 ·
I was testing muzzle energy for different weights to try and get an idea of which BB to use in my CYMA CM.701b (428mm barrel VSR). I found that 0.45g were firing at 1.7J, 0.4g at 1.8J and 0.36g at 1.9J.

The rule you tend to hear is go as heavy as you can hop but there has to be a point at which the initial energy of the lighter BB is so much larger than that of the heavier BB that the effective range of the lighter BB will be higher. Is there a formula for energy loss over distance for given BB weights I can use to determine this?
 
#2 ·
An exact formula? Not that I know of, but you can approach it from an optimum BB for a set velocity kind of thing. For example, if you gun chronos at say 410 fps with a .2g BB, then you can say that a .3 would probably be the optimum BB for that gun. This is strictly a numbers trick, but there are factors in there such as what you're using for a hop.

You are correct, though. As heavy as you can is not always optimum. The r hop in my EBR will lift way over .4g. But, the initial capability of the rifle doesn't provide enough power to take full advantage of the .4. My L96 chronos at 474fps...perfect for a .4g BB. Now, the EBR chronos at 415 fps and can lift a .4, but here's the rub...the magazines have a hard time lifting a .4, especially on full auto. I could use a .36 but that's still a tad heavy to make the system run correctly. .32's are nowhere to be found here, so .3's it is!

So, it's a combination of the many factors that decide which ammo is best. The fire rate, the magazines, etc. Bolt guns don't suffer from this problem so much, but it's still a thing...more than what the chrono says, you might actually have an anomoly where the numbers don't quite make sense, but the physical results do. As long as you're under field limits, fool around with a few different weights and go with good old fashioned trial and error. :)
 
#3 ·
I agree with zero on this one. The "as heavy as you can hop" rule is usually applied when joule limits aren't really being considered. As a rule of thumb, I find that if I'm dropping below 320 fps with whatever weight BB I am using, the BB takes too long to reach its target. Sometimes this isn't a problem if it's a slower paced game, but where I play, gameplay is typically very fast and aggressive which makes for a rather rough time for snipers. Now, as everyone knows, the heavier the bb is, the less it is impacted by external factors like wind and what not. It's ultimately a balance that is up to the user to decide what they would like to trade for what.
 
#6 · (Edited)
It kind of depends how deep down the chairsoft rabbit hole you want to go. I mean you could take a look at the following
ATP - Closing Remarks
Image

Image

and discern given your average engagement distance which BB will get there the fastest, or you could focus on the volume-matching theory where you use whichever BB yields the most energy- and if you wanted to apply both, you'd likely need to alter barrel length.
And all of the above assumes all BBs are of equal quality, which is NOT true >:D

I think personally I would use the following to pick a couple potential BBs to use, then test to see which yields the most energy in your rifle.
https://www.airsoftsniperforum.com/32-general-sniper-talk/37433-magic-marker-s-bb-analysis.html
 
#8 · (Edited)
I made this earlier:
https://docs.google.com/spreadsheets/d/1_ZkGx_l-1dOppvGsG9w7vEiVVOB1CI2co6JkO_1_JtI/edit?usp=sharing

Downloadable Excel file: https://www.dropbox.com/s/v6093fxjeme36h1/Volume and BB Weight Calculator by Sev (Excel).xlsx?dl=0

It won't give you the loss over distance, but it will tell you what weight to run providing you know the cylinder inner diameter, compression stroke length and you can see resulting fps conversion too.
(If you don't know those numbers, use the base VSR numbers 1tonne used of 22.5mm ID and stroke of 90.2mm)
 
#9 ·
I made this earlier:
https://docs.google.com/spreadsheets/d/1zivv54BjB9F3rocH0tUwIKVzhjuW4TPN9qL59ZyJGpw/edit?usp=sharing

It won't give you the loss over distance, but it will tell you what weight to run providing you know the cylinder inner diameter, compression stroke length and you can see resulting fps conversion too.
(If you don't know those numbers, use the base VSR numbers 1tonne used of 22.5mm ID and stroke of 90.2mm)
Can you enable edit access? Or make it so it can be downloaded for offline use?

Also what formula did you use to determine the optimum weight?
 
#13 ·
The formula for ideal weight is:

0.0816497 * √(20r-31)

where r is the cylinder/barrel volume ratio
 
#14 ·
When I click on the values to change them it wont allow me to. The document says it's currently set to "View Only" so that may be why it wont allow any changes.

It would likely be best to make it downloadable instead of allowing any and everyone who is viewing it to change it at will since it is a Live document.
 
#15 ·
When I click on the values to change them it wont allow me to. The document says it's currently set to "View Only" so that may be why it wont allow any changes.

It would likely be best to make it downloadable instead of allowing any and everyone who is viewing it to change it at will since it is a Live document.
Sorry, I was hoping for an interactive online sheet. It's now downloadable though.
 
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#18 ·
Makes sense. Playing around with it all of the calculations are spot on what I would expect for barrel length on a VSR platform.

.43g with my VSR and 430mm barrel is what I've seen give the best results so far, and thats exactly what it calculated.

Nice job!
 
#19 ·
Here are the correct ratios for a VSR10 with different bb weights and an Action Army cylinder. These have the ratio on the end and then it can be converted for your own cylinder volume:


Action Army Cylinder Dimensions
Piston Travel Length: 90.2mm
Cylinder diameter: 22.5mm
Compression Volume: 35864 mm^3


0.3gm bb use a 554mm barrel (15821 mm^3) = 2.26:1
0.32gm bb use a 530mm barrel (15136 mm^3) = 2.36:1
0.36gm bb use a 500mm barrel (14279 mm^3) = 2.51:1
0.4gm bb use a 470mm barrel (13422 mm^3) = 2.67:1
0.43gm bb use a 430mm barrel (12279 mm^3) = 2.92:1
0.45gm bb use a 400mm Barrel (11423 mm^3) = 3.13:1

Also this may help too: AirsoftTech.dk - Calculator to calculate, Speed, Rate of Fire, Gearsets, etc.
You can alter the numbers down the bottom of the page to get the correct barrel length but the lengths above are pretty spot on.
 
#20 ·
Here are the correct ratios for a VSR10 with different bb weights and an Action Army cylinder. These have the ratio on the end and then it can be converted for your own cylinder volume:


Action Army Cylinder Dimensions
Piston Travel Length: 90.2mm
Cylinder diameter: 22.5mm
Compression Volume: 35864 mm^3


0.3gm bb use a 554mm barrel (15821 mm^3) = 2.26:1
0.32gm bb use a 530mm barrel (15136 mm^3) = 2.36:1
0.36gm bb use a 500mm barrel (14279 mm^3) = 2.51:1
0.4gm bb use a 470mm barrel (13422 mm^3) = 2.67:1
0.43gm bb use a 430mm barrel (12279 mm^3) = 2.92:1
0.45gm bb use a 400mm Barrel (11423 mm^3) = 3.13:1

Also this may help too: AirsoftTech.dk - Calculator to calculate, Speed, Rate of Fire, Gearsets, etc.
You can alter the numbers down the bottom of the page to get the correct barrel length but the lengths above are pretty spot on.
Have you done research/calculations for bbs heavier than .45? (Ie. .46, .48, and .49)
 
#21 ·
No. But if you look at the data, you will notice that there is a trend where the heavier the bb, the shorter the barrel. 0.46gm will be about 390mm, 0.48gm is about 370mm and 0.49gm will be similar. From what others have said, 0.66gm is around 300mm.
 
#23 ·
Any idea what the stroke length on Springers piston is? How does an air break effect stroke length?

I have always just shot .40g bbs, but now with this fancy google doc I kinda want to try to optimize it a little better.

Thanks for putting that together Ding!


Sent from my iPhone using Tapatalk
 
#24 ·
It also sort-of depends on your play style. If you lay and wait for your prey, an extra half second to reach your target doesn't matter, but if you're up on a hill and you've been spotted, or you're sniping from a known perch, people can see your BBs coming and just duck, I've been able to do it lmao.
 
#25 ·
Same here, philbegas. I may have been known to even flip the bird to the shooter on occasion as well.:bird: Close...but no cigar. hehehe. That and knowingly standing about 5-10 yards out of range and laughing. Ok, this would be a form of taunting, but also a form of distraction. It tends to give the shooter tunnel vision, as in, wants to shoot you so bad that he doesn't see anything else around....like your buddy walking right up to him from the flank and scoring a point blank kill. Love it when that happens. :tup: Sniper down!:hehe:
 
#26 ·
I've definitely waved to the shooter before hahaha