Calculate Your FPS in Easy and Effective Way

[brihacharan]

Hi Basu / Harsh / Pratik,

> Although we consider "The Method Under Discussion" as a Poor Man's Chrony.... Consider the following:
> The cost of a reasonably good hand held chrony would be between 5K & 8K - This instrument is very common amongst shooters as it gives only a 2% +/- error as compared to a Standard Bench Type Chrono which can cost anywhere from 15K to 20K.
> Now consider the method you're using...
1. Cost of a lap top 25K upwards
2. Authentic software - maybe 10K????
3. The space reqd. / Setting up time + analysis time etc. add to this the big margin of error 8% to 10%!!!!
> Lastly the method used by you is solely depended upon the "Transit Time" of sound produced by AR & Target - here a lot of factors affect the sound waves such as: Wind / Humidity / Ambient temp. + interference of other external sounds.
> Whereas in the hand held / static chrony its the time taken for the specific distance travelled by the projectile within a confined & regulated space that's recorded - Hence more accurate.
> Well this is only a logical observation ....While the method used by you can be an enjoyable DIY
> In this regard my hats off to Pratik for developing a static chrony that has minimal error (costing only a small fraction)- Which can be overcome by having it caliberated with a Branded Chrony
Cheers
Briha

[joywarrior]

Dear Harshvardhan,
Hi,
I was fascinated by your forum post about 'calculating the fps of a gun' using Audacity and other mechanisms described thereof. I am deeply interested in finding the fps of my Air rifle the SDB 150 classic (.22). I also want to learn and be able to implement this system for my own guns in the future. I am a person with very little mathematical intellect and the simplicity with which you have explained the process helped me in setting up the experiment and shooting. Unfortunately the excel sheet that you have posted on scribd is locked under premium membership of scribd . Is there any way that I could get that excel sheet (with all the formulae that it already has), so I may just put my values and get my Fps. Also Your post on this forum using Audacity shows an image depicting distance between two points. I am haplessly unclear whether these two points are two separate shots fired or is it the Trigger fire time to the Target Hit time recorded of one particular shot.The bottom screen shows Start time but there is no time underneath the 'Length' section which shows all as 00.00.00.00. Also very unclear as to why we require 5-6 shots. Is an average out there to be calculated and if yes what is it average of. All these confusions would have been eliminated if I had got the Excel file. Hope to hear from you soon.

Thanking you in Advance,
Joywarrior

[Basu]

Dear jowarrior,
once you put the sound file in audacity SF,you will see some vertical lines appearing based on number of shots fired.select one such line then zoom in the same by clicking the icon.u will notice two peaks,first is the sound of gun and the second one is sound of pellet hitting the target.now click on first peak and drag the mouse upto the second peak.The time consumed,will be reflected below the screen in milisecond like 0.065.Post the same input in excel sheet to get average velocity.Now devide the same by 0.965 and you get muzzle velocity.
Please note that distance is the key factor here and it is to be calculated to nearest inches.

Basu

[harshvardhan]

you can make your own excel sheet....
in audacity you need to measure the time lap between two peaks,
the muzzle sound and the hit sound...
then distance/time....no problem in that..
or if you have a pc mic...
you can try soft chrono....
it is very easy..
follow the link..
http://www.airsoftforum.com/board/Softw ... 89424.html

[pratik_mahale]

Hi Joywarrior

check this link also

http://indiansforguns.com/viewtopic.php ... &hilit=fps

& you can download the software from
https://play.google.com/store/apps/deta ... S5saXRlIl0

[joywarrior]

Dear Mr. harshvardhan, Hi - I just experimented with the home made chrono method to check for the unknown velocity in FPS measurement as suggested by you and a few others, in this forum. Since I could not lay hands on your excel sheet, I attempted to calculate the 6 shots via manually, using your formulae on paper. I do not know if my calculations or the methodology is correct. I tried to use common sense and calculated the fps for each of the 6 shots for two types of pellets namely the heavier 'Mastershot' and the lighter Local brand. I did this by allowing audacity to Check for sound using 'sound finder' and setting the distance between two sound occurrence to .05 sec. I got 384.9 fps on my SDB 150 Classic .22 Air Rifle using a Local Pellet (Lighter in weight - Targetshot), while the reading was 306 fps using 'Mastershot' heavier pellets.I don't know if such differences std/avg deviations are normal with changes in the quality of pellets. Hope my readings were right. I did the same with a 5 year old 'Blanca' Air Pistol and the results seemed to be what I expected avg. at 150fps. It was much easier to let Audacity choose the two sounds - peaks (trigger sound and target hit sound) in a single shot ( a process that I repeated for all the 6 shots), rather than dragging the mouse to select the two peaks of sound (trigger time and target hit time), to find the difference in the time as suggested. So I guess when I buy my gun soon I would be able to verify again. Thank You again for the excellent idea you gave on this forum.

Thank You
Joywarrior

[joywarrior]

Dear jowarrior,
once you put the sound file in audacity SF,you will see some vertical lines appearing based on number of shots fired.select one such line then zoom in the same by clicking the icon.u will notice two peaks,first is the sound of gun and the second one is sound of pellet hitting the target.now click on first peak and drag the mouse upto the second peak.The time consumed,will be reflected below the screen in milisecond like 0.065.Post the same input in excel sheet to get average velocity.Now devide the same by 0.965 and you get muzzle velocity.
Please note that distance is the key factor here and it is to be calculated to nearest inches.

Basu

Hello Sir - I experimented with the home made chrono method to check for the unknown velocity in FPS measurement as suggested by you and a few others, in this forum. Since I could not lay hands on any ready made excel sheet, I attempted to calculate the 6 shots manually, using the formulae on paper. I do not know if my calculations or the methodology is correct. I tried to use common sense and calculated the fps for each of the 6 shots for two types of pellets namely the heavier 'Mastershot' and the lighter Local brand. I did this by allowing audacity to Check for sound using 'sound finder' and setting the distance between two sound occurrence to .05 sec. I got 384.9 fps on my SDB 150 Classic .22 Air Rifle using a Local Pellet (Lighter in weight - Targetshot), while the reading was 306 fps using 'Mastershot' heavier pellets.I don't know if such differences std/avg deviations are normal with changes in the quality of pellets. Hope my readings were right. I did the same with a 5 year old 'Blanca' Air Pistol and the results seemed to be what I expected avg. at 150fps. It was much easier to let Audacity choose the two sounds - peaks (trigger sound and target hit sound) in a single shot ( a process that I repeated for all the 6 shots), rather than dragging the mouse by hand to select the two peaks of sound (trigger time and target hit time), to find the difference in the time as suggested. So I guess when I buy my new guns soon I would be able to verify again. Thank You again for the excellent idea you gave on this forum.

Thank You
Joywarrior

[joywarrior]

Thank you Mr. Basu for your guidance. Would keep them in mind when visiting Kolkata. Wishes and Thanks
Joywarrior

[harshvardhan]

joy warrior ,f you can arrange a pc mike..then softchrono will provide you much accurate result..and even with lots of ease of use....

[joywarrior]

joy warrior ,f you can arrange a pc mike..then softchrono will provide you much accurate result..and even with lots of ease of use....

Ok will try to get a mike and arrange the laptop such that I get a customised home made 'instant' chrono....Even Mr. Basu told me the same thing a lil' while ago.

Thank you
Regards
joywarrior

[joywarrior]

joy warrior ,f you can arrange a pc mike..then softchrono will provide you much accurate result..and even with lots of ease of use....

Dear Sir,

How many pellets must be fired before I can expect the gun to behave normally after the cleaning and oiling process of the Air Rifle. The air rifle I have was ok enough given the local and poor but known quality and most faults were related to shooters errors. But suddenly a day or two ago the gun went totally mad and started shooting pellets 'off' a 1.5 feet by 1 feet target box that I have. I have never seen this gun go mad like this. So I did the drill...checked the screws found one on the gun barrel loose so tightened it, cleaned the barrel with pull through method using anti rust WD solution till the cleaning cloth started coming out clean, set the sights as per centre position default, oiled the gun and yes I minded all the warnings of not putting oil in barrel or breach or cylinder..but on the morning after, I still found lot of dieseling effect, smoke out of every shot...So I fired 30 shots .. the first 4 were bulls eye 20 meters, thereon the next 26 shots were crazy but within the target box and only on one side, lop sided on the left side 3-6 inches...Finally after 30 shots the pellets started missing the box completely again...so I gave up and am taking the gun to a repair shop to test what is the problem. Could not check the seals and washers since I have no knowledge of how to ....Any advice or suggestion would be welcome....did I need to fire 200 rounds before going to the repair shop..I don't know..HELP ! Any and all.

[harshvardhan]

it may be the effect of dieseling
or you iron sight is loose....
check the issues....
then check the barrel screw...
happy shooting.....
in all screws wound cotton thread then tighten them..they will not loose easily

[bennedose]

The screenshot below is the waveform of my SDB rifle being fired and hitting a target. The distance between the first squiggle and second squiggle is the time of travel of pellet. The time is visible and circled at bottom - 0.106 seconds. That is the time taken to travel 10 meters

Speed= Distance/time
Speed= 10 meters/0.106 seconds
Speed= 94.3 meters per second
or speed of pellet=310 feet per second.

rifl.jpg

[harshvardhan]

Now at muzzle it will be approximately
310/.96 =333 fps

[joywarrior]

The screenshot below is the waveform of my SDB rifle being fired and hitting a target. The distance between the first squiggle and second squiggle is the time of travel of pellet. The time is visible and circled at bottom - 0.106 seconds. That is the time taken to travel 10 meters

Speed= Distance/time
Speed= 10 meters/0.106 seconds
Speed= 94.3 meters per second
or speed of pellet=310 feet per second.

rifl.jpg

Dear Sir, I see you have also chosen to select the two sounds physically using your mouse....I would suggest ( and I am no expert) let the software select the two sounds (trigger pull sound and Target hit sound) by going to 'Analyse' Menu and selecting 'Sound Finder'....Set the first option there at 10, the second box below at .05(this you can alter depending on the number of independent sound ranges the software detects, usually it should detect two sound ranges) and the remaining change them to 0. This way there is no element of human error while picking the exact value of where the sound was first created. The whole range of the sound from start to last is mapped by audacity as shown in figure 3. All there is to do is to select the base line of the first and second ranges and we get the value of T1 and T2. The difference can be calculated easily.