KJW M700 diferrent fps and horizontal distance traveled by BBs

[dami]

Originally Posted by CDN_Stalker

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

[Mantelope]

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.

[CDN_Stalker]

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.

[dami]

Originally Posted by harleyb

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 ?F/0.45 : ?F/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.

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

[CDN_Stalker]

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

[Mantelope]

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.

[concept_8]

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.

[dami]

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!!