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Does the weight of bbs affect the fps?


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14 replies to this topic

#1
sarni307

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As above I'm thinking of using .25's tomorrow will this affect my fps I currently use .20
Thanks
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#2
-Ub3R-

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Simple answer: Yes.

If you've got a hot gun and want to bring it under the site's limits using heavier BB's is the way to go. Although it depends how strict the site is.

Generally using heavier BB's will decrease your fps but the BB will fly much straighter and be less affected by wind.

#3
sarni307

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Does it affect the range much?
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#4
Devastator

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It'll be reduced (theoretically) since you're trying to shift more weight with the same amount of power.

#5
bigshep

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Using heavier BB's to decrease FPS is a no no to get through site limits. They have the same energy as a .2 at a higher FPS and are therefore potentially dangerous. For example a 500FPS sniper hits you with one .36g shot, you feel it and it stings. A full auto running at 350 fps on .25's is around 400fps on .2's and on full auto that will hurt a lot (bearing in mind you may be getting hit with 20-30 shots per second in the same area.

As for a 350fps on .2's, it will be around 315 fps on .25's. Range will be the same, within about 5 feet or so. However the bb will take a bit longer to get there, but will be less affected by wind, and foiliage. I like to run .25's as I play in woodland and like to punch through bushes. My gun runs at 340 on .2's and about 310 on .25's, but range is about the same, accuracy is better on .25's

#6
kejot

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Simple answer: Yes.

If you've got a hot gun and want to bring it under the site's limits using heavier BB's is the way to go. Although it depends how strict the site is.



i dont know any site that would allow hot guns to use heaver bb's to pass the site limit, i know f&o use their own mags & 0.2g's to chrono so you cant use hot guns

#7
sarni307

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I've used my gun a fair few times at combat south so I know it's within the limits just was not sure if it actually affects the fps
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#8
kejot

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yes it will but u need to chrono with 0.2 and then check if you can use anything heavier

this might help


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#9
M_P

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That is a good table,thanks
saved

#10
-Ub3R-

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Just to clear it up.
I wasn't recommending using heavier BB's to lower your FPS. Hence I said, 'how strict the site is'.

Some sites just chrono as a formality.
I've seen people chrono one gun then go back to their car and get an M249 and not chrono it into the game. Then get shot by said gun and be bleeding fairly heavily afterwards.

But that's a different topic.
And yes, good table. :)

#11
bigshep

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if I was on the recieving end of said 249, then I would be hollering for an umpire and get him banned for life. This is a hobby where we are playing games. In my mind someone who intentionally goes out to hurt someone while playing a game has no place in the sport.

#12
JEZZ

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I've been doing Airsoft for a long time, 10 + years and the rest. Re this post you are missing a key factor. BB weight only effects stability of flight in wind and as I run a site as Chief Marshall all guns are tested with .2 grm. bb's.
Read below as to what I mean.

PLEASE ALL READ AS IT SAVES A LOT OF AGGRO ON THE FIELD

This has come from demoncase over on

www.ukairsoftzone.co.uk/forums/topic/150...of-taking-your-hits/

So I take no credit for the effort it took to work out the maths and for him, he has done the airsoft world a huge service in providing the facts.

Thank You Demoncase. (www.ukairsoftzone.co.uk)

Read on
Jezz.

Scenario:
You are tucked away behind a tree in a woodland game
The chatter of AEGs is carrying on the wind as your team engauges the enemy on a broad front
You scan the next row of trees for that tell-tale elbow or barrel that indicates the other team lying in wait.
Your RIF is loaded, ready to shoot and the HOP is dead flat out to 50 meters
About 30 meters is the next treeline...Suddenly, in that treeline: movement!
You spot the head and arm of one of the other team poke from behind a tree.
No consicous thought is involved:

What happens now
~Human reaction time from sense to movement starting is about 0.2-0.5s (it varies by person, fatigue levels, experience of the stimulus in question and by stimulus type)
~The movement to raise/aim your weapon takes an appreciable 0.1-0.3s, depending on practice and 'muscle memory'
~So let's be generous and say that from seeing a opponent to aiming your RIF and pulling the trigger takes 0.4s- that's with a well practiced and instinctive reaction from an experienced player.
~30m equates to about 100 feet.
~Your AEG fires at 330fps- the notional 1J 'Yardstick' for UK RIFs
~100feet/330fps= 0.3 seconds (0.3s)
:~Thus It takes 0.3s for a BB to travel from your muzzle to your target 30m away.
~ 0.3s Travel Time + 0.4s Reaction Time= 0.7s Total
Therefore, at 30 metres, the total time from observation to first hit is 0.7s.

At the same time:
~The sound of your AEG travels at over 1100fps. (Note: this varies by about 50fps due to the density of air varying with temperature/humidity but it's never LESS than 1100fps)
~At 30m, the sound takes less than 0.09s to reach your target- 0.21s AHEAD of your BBs.
~Ducking when you hear AEG fire is probably the very first instinct you learn in Airsoft- it's an automatic reaction and thus faster
~Let's say that the 'duck' reaction of your opponent is thus 0.2s
So Time from you pulling the trigger to your target begining to duck is 0.29s
You opponent is therefore already beginning to move as your first BB reaches where they were when you took aim- if it was just an arm you were aiming at then the chances are, at 30m, you've hit the tree they are hiding behind.

So: when you shoot at someone and they duck DON'T automatically bellow "TEK YER HITS YER ***********"
Fundamentally: it's rude and not in keeping with the sportsmanship of the game.
For another it's entirely possible that they heard you AEG and began ducking before the BBs reached them- mathematically and actually possible.

Some 'Caveats'
0: THE BIG ONE: This assumes that your opponent has only heard your shot and was STATIC before you shot
~If they see you at the same time as YOU see them then they have 0.3s in hand - the 0.3s it takes your BBs to travel to them- to dive to cover - while a third of a second might not seem much, it can be the difference between yelling "HIT!" or suddenly getting rounds back from your target!
Likewise, if your target was already moving obliquely to the line of fire (and you didn't lead them enough) then it's likely your BBs are landing where they were, rather than where they are.

1. These figures are idealised-
MOST FUNDAMENTALLY: You may not actually be hitting your target with that first BB.....
EVERY subsequent BB will take 0.3s to reach it's target, (in our example) with the additional delay between shots based on your RPM- with a notional 1000rpm, each BB is 0.06s apart
Thus your next BB is 0.36s from pulling the trigger, the next is 0.42s etc etc.
Initially, You might be slower at getting on target/pulling the trigger- new kit, being out of practice, being cold,tired or overheated all affect this.Your opponent might have a slower reaction time.
What I'm trying to illustrate is that it's entirely possible at even 30m to be ducking, just by HEARING the sound of the gun BEFORE the BBs get to you WITHOUT being a cheating so 'n' so.

2. The automatic reaction to this might be "I'll up me FPS then- the BB's'll get there quicker, innit."....
Sorry- The difference in travel time between a 330fps gun and a 350fps gun is 0.02s- So 0.28s rather than 0.3s...SO small that it won't make all that much difference to the outcome.
EVEN with a sniper rifle doing 500FPS, the travel time at 30m is STILL 0.20s.
AND the sound of your RIF ALWAYS gets there in 0.09s, REGARDLESS of the fps of the BB.
Only very good silencing or getting VERY close are solutions to this!

3. This is at 30m- A distance where most woodland skirmishers will happily enguage an opponent with high confidence of a kill...
Up that to the 50m (160ish feet) common these days then time taken from seeing your opponent to pulling the trigger is now in the region of leisurely 1 full second: plenty of time for your opponent to dive behind another tree!

Conclusions
At 30metres:
1. FPS is largely irrelevant.
2. Stealth, sound supression and accuracy at range are more important than sheer muzzle FPS
3. Not being seen adds an extra 0.3s to your chances of a kill.
4. You will ALWAYS hear the RIF before the BBs get to you- unless it's perfectly silent.
5. The best way to increase your kill ratio is to improve your reaction time with PRACTICE and STEALTH.
6. When being shot at from 30m, the best thing to do is MOVE rather than begin shooting back.

At 50metres
1. There will be approximately 1 second between seeing and hitting your target.
2. 1 Second is plenty of time for your opponent to duck, run, dive or begin shooting back (or open a newspaper and start doing sudoku)

#13
Devastator

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Very nice 'theoretical' post even if slightly irrelevant to what has been asked. Would be great to see it added to with some more 'real world' physics used in the calculations, I think you'd find that the gap for reacting would be increased by a fair amount.

BB weight only effects stability of flight in wind


Re the above, yes but it does also affect the FPS of the BB. It shouldn't be assumed heavier ammo will result in the gun firing the same FPS.

#14
JEZZ

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Should have put this first though (Hindsight) , be interesting if the 2 tables match.

http://ukairsoftzone...eight-to-power/

Jezz.

#15
Devastator

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Short answer:
On the measurements that are the same, they are identical.

However:
The table you linked goes up in random amounts where as the one above just increases in 0.25J. You'd probably get a nicer shaped curve if you were to use the initial table (the one with the 0.25J steps).




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