f.p.s

[pestcontroller4u]

i have just purchased an aa s410k and i intend to do some testing with 3 different brands of pellets to find out which pellets have the better f.p.s over 60 shots and to also find the sweet spot.how do i work out the fps spread over the 60 shots?

[Dekers]

Perhaps I missed something in the question, but to get the FPS at all you will need a chrono!

 

Many have inbuilt programs to calculate averages etc, if not, simply record the speed of every shot and then divide by the total shots to give an average!

 

To get the spread, it's the lowest to highest speed!

Edited November 30, 2010 by Dekers

[pestcontroller4u]

Perhaps I missed something in the question, but to get the FPS at all you will need a chrono!

 

Many have inbuilt programs to calculate averages etc, if not, simply record the speed of every shot and then divide by the total shots to give an average!

 

To get the spread, it's the lowest to highest speed!

yes i have a chrono to do this,i just was not sure on how to work the overall spread out.

[inshallah]

If you are going to the trouble of shooting 60 shots for different batches of pellets, it would be well worth plotting the results. You could do this in Matlab or Octave or something similar, or even excel if you must. Plot f.p.s on the vertical axis against shot number. Then you should be able to see the flattest part of the power curve. Plotting all the pellets on the same plot would be interesting. (Make sure you start at the same pressure.)

 

Variation between shots will be seen as more scatter on the curves. If you want a numerical indication of the shot-to-shot scatter you could fit a parabola to the measurements and look at the chi-squared value from the fit.

 

If you get some results then please post them on PW. I've wanted to do this for ages with my .22 S310, but I don't have a chrono., so I'd love to see your results.

 

If you just post the values I'll plot them if you like. Might even do the parabola fit, but not promising because with college 4 days a week and work 3 days, I'm a bit busy...

[John_R]

yes i have a chrono to do this,i just was not sure on how to work the overall spread out.

 

If that is all you want, simply subtract the lowest figure from the highest, and that is your overall spread. If you are wanting more statistical numbers then you have a little more work ahead of you.

[pestcontroller4u]

If you are going to the trouble of shooting 60 shots for different batches of pellets, it would be well worth plotting the results. You could do this in Matlab or Octave or something similar, or even excel if you must. Plot f.p.s on the vertical axis against shot number. Then you should be able to see the flattest part of the power curve. Plotting all the pellets on the same plot would be interesting. (Make sure you start at the same pressure.)

 

Variation between shots will be seen as more scatter on the curves. If you want a numerical indication of the shot-to-shot scatter you could fit a parabola to the measurements and look at the chi-squared value from the fit.

 

If you get some results then please post them on PW. I've wanted to do this for ages with my .22 S310, but I don't have a chrono., so I'd love to see your results.

 

If you just post the values I'll plot them if you like. Might even do the parabola fit, but not promising because with college 4 days a week and work 3 days, I'm a bit busy...

you have baffled me with all this matlab/octave stuff,im simply going to chrono with 3 different brands of pellets and at 3 different pressure fills per brand of pellet,i will then subtract the lowest fps from the highest to find the overall spread and then post my findings

[UKPoacher]

i have just purchased an aa s410k and i intend to do some testing with 3 different brands of pellets to find out which pellets have the better f.p.s over 60 shots and to also find the sweet spot.how do i work out the fps spread over the 60 shots?

 

If you don't understand how to achieve an average or a spread from a series of figures how the hell is that going to help you? :blink:

 

Why 60 shots? Why not just 10? Or 100? What is a better f.p.s - the highest or the most consistent?

 

 

you have baffled me with all this matlab/octave stuff,im simply going to chrono with 3 different brands of pellets and at 3 different pressure fills per brand of pellet,i will then subtract the lowest fps from the highest to find the overall spread and then post my findings

 

You and me both mate

Edited November 30, 2010 by UKPoacher

[Sha Bu Le]

I'm with UKP its got to be consistancy (the most frequently occuring or modal value) 60 per pellet seems excessive, given the manufacturing accuracy of decent quality brands I would have thought 20-30 should be sufficient to give a reliable modal value.

Edited November 30, 2010 by Sha Bu Le

[pestcontroller4u]

If you don't understand how to achieve an average or a spread from a series of figures how the hell is that going to help you? :blink:

 

Why 60 shots? Why not just 10? Or 100? What is a better f.p.s - the highest or the most consistent?

 

 

 

 

You and me both mate

i have chosen 60 has this is what i beleive is the amount of shots you get before the power starts to drop off

[inshallah]

i have chosen 60 has this is what i beleive is the amount of shots you get before the power starts to drop off

 

I don't really understand the experiment you're trying to do. You say you will try 3 different pellet brands at 3 different pressures. But you also say you will do 60 shots. Is this all at the same pressure? Will you pump the gun up after each shot? Or if you don't, you have a different pressure each shot?

 

The way to do it is to fill the gun up to max, fire your 60 pellets (first brand) and take a chrono reading for each one. Then pump it up again and go on to the next brand of pellets, shot another 60 and record all the velocities. Then do the next brand. Then you have a record of each pellet over the whole pressure range. Just from the list of numbers you will get some idea of when the power drops off and and also some idea of the shot to shot consistency.

 

What I was suggesting in my previous post is if you plot these numbers on a graph you should see a nice curve. I would expect the power to drop off at both ends of the pressure range (very high pressure and when the pressure drops very low). In the middle you will hopefully see a nice flat part of the curve (typically with a pressure of 160 down to 120 or so) where the power doesn't change much. You then know that if you keep your gun in this pressure region, the accuracy will be OK as far as pressure goes.

 

The other thing that effects accuracy is the shot to shot consistency. Again, from the list of numbers, you can see if the velocity jumps around a lot. But if you plot the results (same plot as before, just plot the velocity against shot number) you will visually see how much the velocity jumps around shot to shot. If you get less scatter on one of the brands of pellets, that might be the one to go for. You might also see that the shot-to-shot consistency varies at different parts of the power curve for different pellets. My S310 less consistent at higher pressures for example. This will be obvious from the plot too - just look at the amount of scatter you have at different parts of the power curve.

 

Probably the easiest way to produce the plot is just to type the numbers from one of the pellet runs into a single column in excel, select that column and then just plot it as a line or scatter plot. You will then see the power curve and the scatter. Do the other pellet brands just the same. You can also plot all the pellet brands on a single graph, in different colours, and then you will very easily be able to see which one's the best.

 

The next step is only of you're feeling very geeky. It's a bit harder to do, but it will give you a numerical value of the shot to shot consistency and make the graph easier to see the scatter.

What you need to do is fit a curve through the points. Think of this as a 'model' of your power curve. If the gun was 'perfect' in terms of shot-to-shot consistency then all the readings would fall exactly on this line. In reality there will always be some inconsistency, so each velocity will be slightly off the line. Plot the curve on the same plot as the measured results. The better the pellet, the closer to the 'ideal' line they would be. You can also turn this into a single number that describes the shot-to-shot performance by summing the differences of the squares of the model and data at each point. The one with the lowest number might be the best pellet. The model that you use would be

 

2

v = a(n-n0) + b(n-n0) + c

 

v is the velocity and n is the shot number. You have to calculate a, b and c and n0 to be values that produce the best fit of the curve to your measurements. You will need a computer and and statistical software to do this. You can do this in excel by using 'fit trendline -> polynomial -> order 2'

I've attached a plot that I've just made with simulated data (I don't have a chrono) to show you what it should look like

pelets.tiff

[Lez325]

i have just purchased an aa s410k and i intend to do some testing with 3 different brands of pellets to find out which pellets have the better f.p.s over 60 shots and to also find the sweet spot.how do i work out the fps spread over the 60 shots?

 

 

Chrono- no other way around that

 

Les

[UKPoacher]

To be perfectly honest all this testing and plotting makes very little difference in real terms. Take a ten shot string at a target at say 30yds, and I would bet that you wouldn't notice the difference on POI if your gun varied one foot pound either way.

 

Modern air rifles, even some of the cheaper ones are far more consistent than the shooter.

[paul87]

very well explained inshallah, it makes sense to go to the extra trouble, once the numbers are recorded, to fully understand the optimum performance of the air rifle and best pellet for the job especially where shot to shot accuracy is required.

[pestcontroller4u]

maybe i should have explained my intentions better,all i am trying to do is find the sweet spot of the rifle and to find which of the 3 brands of pellet gives the better shot to shot consistancy.i have up to now filled to a 190 bar fill and using aa field 4.52 have chrono'd and recorded 60 shots,is was not until the 23rd shot that the power went up into the 11ftlb bracket,i think i will need to fill to 170bar to get a good 50-60 shots in the sweet spot.

[inshallah]

To be perfectly honest all this testing and plotting makes very little difference in real terms. Take a ten shot string at a target at say 30yds, and I would bet that you wouldn't notice the difference on POI if your gun varied one foot pound either way.

 

Modern air rifles, even some of the cheaper ones are far more consistent than the shooter.

 

When I bought my S310 I had all sorts of trouble with it. OK, it's a 10 year old gun, and maybe it needs a service, but I couldn't hit (inanimate) targets consistently. I spent 3 months practicing and trying to learn how to shoot. Eventually I convinced myself it wasn't me, it was the gun.

 

After a lot of testing I found that it shoots very straight with Bisley Magnums with a pressure of between 120 and 150 bar. AA Fields, JSB exacts and many others just spray around all over the place. I have chrono'd a few shots with it at my local club just to make sure it was at the right power (11.2 ft lb measured). But the test I have described on this thread is exactly what I needed to do to sort out the problem, and it would have saved me weeks of guessing if I'd had a chrono and could have done the tests.

 

Now, at the club, resting the gun on a pile of carpet tiles, I can hit a pound coin sized object at 35 yards pretty much every time with the bisleys and at the right fill presure. With any other pellets I'd be lucky to hit a tennis ball every shot. The down side is that Bisley Magnums in .22 drop like bricks, and this limits my hunting range to about 28 yards due to my chosen zero of 25 yards. I'm not a great shot, so in the field shooting from, e.g., a sitting position, this is about my limit anyway, so it's not too much of a problem. 45 yard rabbiting is out of my league.

[pestcontroller4u]

To be perfectly honest all this testing and plotting makes very little difference in real terms. Take a ten shot string at a target at say 30yds, and I would bet that you wouldn't notice the difference on POI if your gun varied one foot pound either way.

 

Modern air rifles, even some of the cheaper ones are far more consistent than the shooter.

if this is indded the case i could get more shots from a fill rather than trying to find the correct fill pressure for the sweet spot?

[John_R]

To be honest, why not go to the AA Owners club web site, and have a look round there? You are highly likely to find others have already found the sweet spot and other such info, and that could get you on the right track a lot faster.

 

Sweet spots do make a difference, I found that if I go over 160 Bar in my Daystate the power dropped off enough to matter at longer range.

 

As for pellets, I bet you'll find the AA Fields and JSB Exacts are the ones you settle on.

[turbo33]

To be honest, why not go to the AA Owners club web site, and have a look round there? You are highly likely to find others have already found the sweet spot and other such info, and that could get you on the right track a lot faster.

 

Sweet spots do make a difference, I found that if I go over 160 Bar in my Daystate the power dropped off enough to matter at longer range.

 

As for pellets, I bet you'll find the AA Fields and JSB Exacts are the ones you settle on.

 

Bang on John, good call I have found 165 down to 100 the sweet spot on my AA's and found that from advice of others with them. I now only fill to 165. The only other experimenting to do is with different sizes of AA pellets. Mine all prefer 4.52's. There was no difference with the JSB's who I believe make the AA pellets anyway. I have found the AA diablo field the most accurate and deadly pellets so never use anything else.

[pestcontroller4u]

Bang on John, good call I have found 165 down to 100 the sweet spot on my AA's and found that from advice of others with them. I now only fill to 165. The only other experimenting to do is with different sizes of AA pellets. Mine all prefer 4.52's. There was no difference with the JSB's who I believe make the AA pellets anyway. I have found the AA diablo field the most accurate and deadly pellets so never use anything else.

im trying aa field 4.52,jsb exact 4.52 and bisley magnums

[kent]

i have just purchased an aa s410k and i intend to do some testing with 3 different brands of pellets to find out which pellets have the better f.p.s over 60 shots and to also find the sweet spot.how do i work out the fps spread over the 60 shots?

Don't be too conserned with FPS at muzzle other than staying legal, far more important is downrange spread. You can put the chrono downrange to find this however consider trying different pellets and different fill pressures to build a picture of what works for your gun as regards accuraccy.

[The Duncan]

chrono'ing has its place, but try shooting 60 pellets in 10 shot strings at, say, 35 yards and note group sizes and vertical drop through the string.

This will give you a good idea of when power drops off where it counts - at target.

It should also demonstrate the rifles accuracy and consistency generally. A good exercise.

Edited December 1, 2010 by The Duncan

[inshallah]

Here's the results from pertcontroller4u's rifle, just in case anyone's interested.

 

Looks pretty good between 120 and 160. I'm not sure if the scatter is genuine shot-to-shot variation or the error associated with the chrono. Just depends on how good the chrono is! Probably a bit of both.

 

Really drops off at low pressure just as I have seen from my S310 from looking at the point of impact.

Edited December 2, 2010 by inshallah

[The Duncan]

Here's the results from pertcontroller4u's rifle, just in case anyone's interested.

 

Looks pretty good between 120 and 160. I'm not sure if the scatter is genuine shot-to-shot variation or the error associated with the chrono. Just depends on how good the chrono is! Probably a bit of both.

 

Really drops off at low pressure just as I have seen from my S310 from looking at the point of impact.

 

Thanks for your consideration; I'm definitely interested.

I was thinking whilst looking at the graph - "120-160 seems about right".

 

I might even try it with my HW100, but right down to 90bar the poi doesn't seem to drop at all, so probably not worth my effort .

I think Weihrauch put a regulating chamber in the rifle (so they can claim it's unregulated), which negates the 'sweet spot idea'. That or the sweet spot is 200 bar to 90 bar

Thanks again Inshallah