KJW M700 diferrent fps and horizontal distance traveled by BBs
 

The tables shows how different weight BBs would work with your m700 clone.
The formula is:

m1/m2=V2/V1

can be applied to find fps or m/s and then convert.
m1 and m2 is the weight of BBs. Starting with store 0.2g BB at 500fps and
keep going.

The formula is the horizontal maximum distance traveled by a BB=Xmax:

Xmax=Vinitial * (radical of (2*h/g))

Vinit= initial speed of BB when leaving the barrel
h=1m(measurements made at 1m height)
g=9.81m/s2(gravitation)
example 0.36g
Xmax= 83.33 * (radical of(2*1/9.81))=37.62m
To find the m/s or fps of your beloved m700 using 0.36g BBs:
m1/m2=V2/V1--->0.2/0.36=V2/150----->V2=(150*0.2)/0.36--->V2=83.33m/s

(150m/s)500fps-----------------------------0.2g_____Xmax=67.72m
(120m/s)400fps-----------------------------0.25g____Xmax=54.18m
(107.14m/s)357.14fps--------------------------0.28g____Xmax=48.37m
(83.33m/s) 277.77fps--------------------------0.36g____Xmax=37.62m
(69.76m/s) 232.55fps------------------------0.43g____Xmax=31.49m

These are measurements made on paper with formulas without taking in consideration the wind speed, rain, temperature or even the air friction.
Use them if you wish. They are accurate if the M700 is left to the same speed. If tweaked to higher speeds with 0.36g to reach 400~fps not sure if a smart idea. As you see it's already around 280~fps but for some people that's not enough.
Have a look and tell me what you think,
Danny

hop-up?

assuming the hop-up is fixed(found the right position for it), which data is being given to us...at least that's the way I see it. It doesn't say anything that's your suppossed to position hop-up max or min. I suppossed minimun.

So, assuming the hop up is "off" then?

I only ask because the forumula assumes a regular projectile path, right?

Adding backspin would change the formula to be quite a bit different, I thought.

It should not make lots of difference, but you're right..... the first formula 1 calculates the speeds and weight and the second(Xmax) 2 calculates maximum horizontal projectile distance(BB).... including the height, and initial speed of BB for a KJW M700 stock.

also, this doesnt factor in the fact that the gas expelled by the gun to push the bb out is more than is needed. in other words, when a lighter bb is expelled, a smaller amount of gas is pressurized behind it in the barrel because it moves faster than a heavier bb would. the excess gas just poofs out after the bb leaves the barrel, thus a heavier bb would use more of that poof to power it out which explains why chronied shots of the gun, using different bb weights, resulted in shots with similar velocities. heavier bb's, because they use more of the energy supplied by the gas, carry more energy (the chart becomes non-linear) and thus travel further.

the idea behind this table is the Force applied to the BB cocked. Once the trigger is pulled it will release the same amount of gas, no matter if the BB is 0.36 or 0.20 or even 0.43g. Of course the amount of gas will increase/decrease if you tweak with it. I found from other postings that it is under the bolt. The hop-up didn't take into consideration. Left it off. Another thing, m700 is not a computer/human to know if you added a ligher/heavier BB to the mag. That's why I'm considering the same amount of gas being "poofed" along with the BBs.

i'm not saying a different amount of gas is expelled depending on the bb weight, i'm saying a different amount of energy is transferred to differently weighted bb's because of the speed at which they exit the gun. if a heavier bb moves slower out of the barrel, the gas behind it is under high pressure until it leaves the barrel. a lighter bb moves faster out of the barrel thus the gas behind it would be less pressurized.

Just a thought, but I've previously found 0.36g BBs to fly about 100fps lower than 0.20g BBs from the same gun. That's from chrony results in my M24. Hadn't done a lot of testing with my M700 though, aside from 0.20g BBs.

My $0.02 worth.

Though I might share.
I did the calculatios of barrel length and starting pressure.

Very interesting litte math exercise.

I could plot the velocity of the bb as it travels down the barrel and the drop in pressure. I could also find the time it takes to clear the barrel (ie, if someone wants to investigate the suck back theory).

I could also find the difference in barrel diameter and if I had a chrony I could calculate fricton and back force exerted by the air before the bb through empirical methods.

manchovie what you are saying is right. if BB is lighter it will be pushed with greater force, therefore greater m/s, higher enegy(but I don't know where you are going with this).
Here only the initial speed determined is used by the second formula(Xmax). Weight of the BB is considered to find that initial speed to clear barrel with.
In the table those are virtual calcs from barrel tip to whereever the BB will start falling to the ground.
Danny

how were the 0.2g testing results?
Danny

Well, let's just say after the first 3 shots, temp was the hottest day we had this summer, about 43C with the humidex, they settled down to about 550fps. Duster ran in under 450fps with the same conditions, fps sat between 435 and 445fps. Is why I insist people use duster in hot weather, and pay attention to engagement distances, no closer than 100ft. Propane works well in cooler weather, we played and the M700 was used all day on Nov. 16th, temp went to a high of +10C that day, and the M700 worked just fine (mags kept in pockets) and no one hit complained at all. I used my M24/MP5 all day, let a friend use the M700 (he played on the other team, so we were his targets).

Checking your figures out more now and comparing them to my experiences with the M700, using propane 0.36g BBs fly out to about 150ft (45m) then drop right off. Not enough hop up available to make them fly farther. 0.43g wouldn't go much farther. 0.30 and .29 SGM are ideal for the M700 (sure 0.28g are fine as well, I just haven't used them), but 0.20 and 0.25g are too light to effectively use.

Oh man 43Celcius...that's freaking hot, You'll get "barbequed" under the sun.
CDN_Stalker did you leave the settings as they were or you played around with them a bit to reach higher fps for 0.36g BBs?
Never used Duster, only Propane and Green Gas..that was on my pistol(Dark Hawk).
What's the name of the duster you used?
Danny

Ya, 43C with the humidity, actual temp was about 36C. I actually did a couple things to drop the fps down, one was to trim off a couple coils from the striker spring (hits too hard) yielding a more level gas release (hae a Tanaka striker spring on order as recommended), and backed off the loading adustment rod (striker spring guide rod) a bit (found that mine only turns 1/4 turn when it should be 2 full turns).

Duster, not sure the brand, but it was the tetraflouroethane, I make sure of that when I buy the stuff (only need it now for the M700, all my other GBBs use propane.)

Only played counter sniper up to now...wanna see if sniping can bring the adrenaline level even higher.
You say it hits too hard...does it matter if u use .36gBBs(graphite coted ones) or .43gBBs. Let's say you take it from the box, do you actually have to trim the coil, turn down the fps from the screw...or should be just fine as it comes.
Danny

Your original table is flawed. It's assuming that the kinetic energy of the BBs is the same at the muzzle, when in fact, heavier BBs will have more KE because the force applied by the gas will have longer to act on a heavier BB as it accelerates down the barrel.

F=ma, right? Assuming a constant force, (this is plausible at least in the gas pistols i've studied because of the floating/backpressure valve) acceleration is inversely proportional to the mass, a=F/m
final velocity can be found with vf^2 = vi^2 + 2ad
assuming a 500mm barrel vf = sqrt(0 + 2*0.5*F/m) = sqrt(F/m)
so hypothetical exit velocity of a 0.2g BB compared to a 0.36g is sqrtF/0.45 : sqrtF/0.6
this means that the 0.36g BB will be about 25% slower, even though it's almost 75% heavier.

if your M700 is shooting a 0.2g at 500FPS, it should hypothetically be shooting a 0.36g at 375FPS, and not the 277FPS you stated.



Edit: I forgot to mention that all of this is completely invalidated because of hopup. To get a straight flight path, the heavier your BB, the more hop needs to be applied. This gets into extremely complicated physics.

Hence the need to wash the graphite off your heavier (Straight) BBs. The graphite acts like a dry oil, it coats your hop up with slippery graphite, causing you to lose friction, thereby adding more hop up to compensate, resulting in lower fps out of the muzzle.

Overall, from my experience with my M700, if you want max range, don't use anything heavier than 0.30g BBs. The fps will spit them out fast enough to reach the point farther away when the lift caused by hop up takes over from fps. Can easily get 200ft out of a 0.30g BB on propane, even if the temp is +10C. Duster will do the same at hotter temps.

I only cut a couple coils off my spring, Dami, and was satisfied with the results. Was only after that point that I read you CAN indeed adjust the striker spring tension, tried it to find I could only get a 1/4 turn out of it, not worth following.

That's what I wanted ..prove me wrong. I'll recheck my calculations tonight. I see where you are going with this. Hopefully next time I'll get them right.
Thanks you and all,
Danny

Better to just get chrony results. Hey, sue me, I'm simple (online anyways, different on the field! :twisted: )

Even if we're going with equal muzzle energy, your math is still incorrect. 150m/s at 0.0002kg = m/2 * v^2 = 2.25J
v = sqrt(2.25*2/0.00036) = 112m/s, not the 83 you have up there.

If you realy want to get the distance of bb travel correct don't forget to compensate for bb decay so to speak, (the farther from the muzzle the bb gets the more energy lost leading to a more rapid drop as it travels).
Without hop up it might be easier to compensate for decay or drop, but once you throw hop up into the equation the variables might just be infinite and way to much to precisely account for.

As it stands it looks like the numbers you've come up with are a generic bb weight+fps=distance which might be usefull in figuring out what distance one would acheive using different weight bb's in a single specific gun that is running consistant fps with say .20's.
I don't see anything dealing with specifics of the gun itself or the bb's for that matter though since from model to model and even gun to gun of the same model variables would change dramtically, and from bb brand to brand some changes are likely also.(size, material make up, shape,)

Even still though as a specific chart for a single model, you have a couple of variables to compensate for (harley's suggestions, decay, bb consistancy, and any more you can figure out like temp humidity ect. if you realy want to crunch out all the details) and it might end up close to precise.

Good luck n keep at it, n maybe in the end you'll have a usefull chart that can be helpfull for m700 owners and maybe even easily tweakable for other models also.

AFTER I'M GETTING MY M700, DO CHRONY, SOME PPL SAY MY TABLE ANSWERS AREN'T RIGHT!!! AFTER CHRONNING I'LL MAKE SURE OF THAT!!