New VFC VR16 mod 0 saber low fps

[shavas]

Hi all, I bought a new VFC Vr16 mod-0 saber (full length version) last week and played on the weekend at Panther. I had .25 bb's and when I had it chono'd it only shot at about 325fps. I was using a 11.1 lipo battery. I was expecting it to shoot 370-390fps as that's what all the reviews said and also the store I bought it from said it would shoot 390 fps. Im going to call the store later today and also ask. But does anyone know why a new stock VFC VR16 might be shooting at 325 fps instead of 370+?? Thanks in advance for anyone who can help!

[Red Dot]

Is the hop-up cranked up?

[EOD Steve]

370-390fps is clocked with .20g ammo.

You're using 0.25g ammo to chrono. AEGs have fixed power ouptut. Simply put - when you feed a gun heavier ammo, the FPS will lower because it can only pump out a fixed amount of energy.

[BioRage]

[shavas]

I was probably about 6 clicks positve on the hop-up. Should I have had the hop-up on zero? Didn't think about that at the time. Also it was pretty cold out and raining but not sure that would have affected anything or not.

[shavas]

Originally Posted by EOD Steve

370-390fps is clocked with .20g ammo.

You're using 0.25g ammo to chrono. AEGs have fixed power ouptut. Simply put - when you feed a gun heavier ammo, the FPS will lower because it can only pump out a fixed amount of energy.

Yeah I was just reading the fps can drop 30-50fps going from .20 to .25g ammo. didn't think about that before. Does anyone here have any experience of how fast a VR16 should shoot with .25g (stock).

[BioRage]

Should be anywhere from 16-20 RPS as per google, on 11.1 (stock)

[shavas]

I was looking at an energy chart for airsoft guns and at 328fps for .25g bb would have 1.25j of energy. Does anyone know if that's in the ballpark for a stock VFC?

[pestobanana]

VFCs nowadays generally shoot 360-400 out of the box. It is a range, not an exact specification. There is nothing wrong with your gun.

[BenG]

FPS is such a poor measurment, use the formula Ek=0.5(m)(v)^2 where v is the velocity in meters per second, m is the mass in kilograms Ek is the kenetic energy.

To convert FPS to mps either use the google calculator for it or if you want a rough estimate go fps/3.3 ex: 390/3.3= 118.18mps

to get your bb weight from grams to kilograms divide by 1000 ex: 0.20/1000= 0.0002kg

then calculate the energy Ek = 0.5(0.0002)(118.18)^2 = 1.396j now, we can take this energy and find out what your fps should be on .25g bb by rearranging the formula to the following root(2Ek/m)
your new bb weight: 0.25g = 0.00025kg

so root(2(1.396)/0.00025)=105.67mps which is roughly 348fps which you are 30 shy from, or in terms of the energy your currently producing at 328fps /w.25g bb 1.234j so your "missing" 0.162j of energy from the max quoted potential of your gun, or 0.02311j from the lowest quoted potential for your gun (I didnt show the math for this last one).

So what we can deduce from this math is that you could be:

1) on the low end of the 370-390fps quoted for your gun AND you are reverse joule creeping a tiny bit, which means your having a minor voluming issue, or one of the slew of things that causes joule creep,

OR

2) you could be on the high end of the fps spectrum quoted and have some slightly larger reverse joule creeping issues, either way its perfectly normal.

Its typical for (stock) AEGs to loose some energy when going to a heavier bb, if you chrono your gun on .20g bbs to be around 370 fps I wouldn't worry at all, if you chrono it at 390fps on .20g id have someone redo the voluming in your gun, the easiest way would be by getting a slightly tighter barrel (0.01mm tighter should do the trick, ex: if your at a 6.04 go to a 6.03, etc) or messing with the cylinder, you could also try lightening the piston, this wont give you much but as your only loosing a tiny amount it could be enough. You dont have to do this, but typically I always over volume my AEGs slightly because im more concerned with not loosing energy on heavy weight bbs then I am with getting a bit more efficiency. Regardless, this is perfectly normal and I wouldn't expect anything less from any stock gun, and furthermore the extra inertia that you get from having a heavier bb far outweighs the loss of energy in either case. Your better off running the .25s or heavier no matter what you choose to do, even if you just leave it.

[shavas]

Originally Posted by BenG

FPS is such a poor measurment, use the formula Ek=0.5(m)(v)^2 where m is the velocity in meters per second, m is the mass in kilograms Ek is the kenetic energy.

To convert FPS to mps either use the google calculator for it or if you want a rough estimate go fps/3.3 ex: 390/3.3= 118.18mps

to get your bb weight from grams to kilograms divide by 1000 ex: 0.20/1000= 0.0002kg

then calculate the energy Ek = 0.5(0.0002)(118.18)^2 = 1.396j now, we can take this energy and find out what your fps should be on .25g bb by rearranging the formula to the following root(2Ek/m)
your new bb weight: 0.25g = 0.00025kg

so root(2(1.396)/0.00025)=105.67mps which is roughly 348fps which you are 30 shy from, or in terms of the energy your currently producing at 328fps /w.25g bb 1.234j so your "missing" 0.162j of energy from the max quoted potential of your gun, or 0.02311j from the lowest quoted potential for your gun (I didnt show the math for this last one).

So what we can deduce from this math is that you could be:

1) on the low end of the 370-390fps quoted for your gun AND you are reverse joule creeping a tiny bit, which means your having a minor voluming issue, or one of the slew of things that causes joule creep,

OR

2) you could be on the high end of the fps spectrum quoted and have some slightly larger reverse joule creeping issues, either way its perfectly normal.

Its typical for (stock) AEGs to loose some energy when going to a heavier bb, if you chrono your gun on .20g bbs to be around 370 fps I wouldn't worry at all, if you chrono it at 390fps on .20g id have someone redo the voluming in your gun, the easiest way would be by getting a slightly tighter barrel (0.01mm tighter should do the trick, ex: if your at a 6.04 go to a 6.03, etc) or messing with the cylinder, you could also try lightening the piston, this wont give you much but as your only loosing a tiny amount it could be enough. You dont have to do this, but typically I always over volume my AEGs slightly because im more concerned with not loosing energy on heavy weight bbs then I am with getting a bit more efficiency. Regardless, this is perfectly normal and I wouldn't expect anything less from any stock gun, and furthermore the extra inertia that you get from having a heavier bb far outweighs the loss of energy in either case. Your better off running the .25s or heavier no matter what you choose to do, even if you just leave it.

Thank you for that detailed answer, so much to learn when starting off in airsoft!

[Red Dot]

Fook dat is a lot of numbers mate, me eyes went crossed rite dare.

[Desmodus]

Originally Posted by BenG

FPS is such a poor measurment, use the formula Ek=0.5(m)(v)^2 where m is the velocity in meters per second, m is the mass in kilograms Ek is the kenetic energy.

To convert FPS to mps either use the google calculator for it or if you want a rough estimate go fps/3.3 ex: 390/3.3= 118.18mps

to get your bb weight from grams to kilograms divide by 1000 ex: 0.20/1000= 0.0002kg

then calculate the energy Ek = 0.5(0.0002)(118.18)^2 = 1.396j now, we can take this energy and find out what your fps should be on .25g bb by rearranging the formula to the following root(2Ek/m)
your new bb weight: 0.25g = 0.00025kg

so root(2(1.396)/0.00025)=105.67mps which is roughly 348fps which you are 30 shy from, or in terms of the energy your currently producing at 328fps /w.25g bb 1.234j so your "missing" 0.162j of energy from the max quoted potential of your gun, or 0.02311j from the lowest quoted potential for your gun (I didnt show the math for this last one).

Fucking math. I hate math.

[pestobanana]

Originally Posted by Desmodus

Fucking math. I hate math.

Should have just been born an Asian.

[shavas]

I spoke to the owner of the store, he said the chrono at the field where I was playing reads low. Also said to bring it in to the store and they would test it and if it is sub-par at all that they'll tune it up!