pellet velocity chart

[Miguel]

Hello All,
I wonder if there is any way to prepair an easy chart with the readings of the chronograph to have a clear idea of the air gun consistency.
Or any database already prepaired, (I´m not very good with excell)
Thank you all

[WIanB]

I have created an excel spreadsheet that will do that. You are more than welcome to have a copy. I'll have to change it a bit so that it doesn't show "ILLEGAL" for over 12ft/lbs. 12ft/lbs is our power limit here in the UK.

[Scotchmo]

Hello All,
I wonder if there is any way to prepair an easy chart with the readings of the chronograph to have a clear idea of the air gun consistency.
Or any database already prepaired, (I´m not very good with excell)
Thank you all

You don't necessarily need to use a chart. You could use something as simple as this:
http://www.calculator.net/standard-deviation-calculator.html

Enter the velocity readings and get your Average and Standard Deviation.

For consistency, an SD of 1% of the average is barely OK for my target guns. I prefer to see a 1/2% or even less.

So an 800fps average needs to have an SD of 8fps or less.

[RAJOD]

Hello All,
I wonder if there is any way to prepair an easy chart with the readings of the chronograph to have a clear idea of the air gun consistency.
Or any database already prepaired, (I´m not very good with excell)
Thank you all

You don't necessarily need to use a chart. You could use something as simple as this:
http://www.calculator.net/standard-deviation-calculator.html

Enter the velocity readings and get your Average and Standard Deviation.

For consistency, an SD of 1% of the average is barely OK for my target guns. I prefer to see a 1/2% or even less.

So an 800fps average needs to have an SD of 8fps or less.

At what distance does that 1% SD start to make a noticeable difference?  I can see 30 yards it might but not 10.

[Scotchmo]

Hello All,
I wonder if there is any way to prepair an easy chart with the readings of the chronograph to have a clear idea of the air gun consistency.
Or any database already prepaired, (I´m not very good with excell)
Thank you all

You don't necessarily need to use a chart. You could use something as simple as this:
http://www.calculator.net/standard-deviation-calculator.html

Enter the velocity readings and get your Average and Standard Deviation.

For consistency, an SD of 1% of the average is barely OK for my target guns. I prefer to see a 1/2% or even less.

So an 800fps average needs to have an SD of 8fps or less.

At what distance does that 1% SD start to make a noticeable difference?  I can see 30 yards it might but not 10.

Velocity variation at 10 yards is almost inconsequential.

Keeping 1% variation helps the long shots.

With a muzzle velocity of 800fps, an SD of 8fps, and distance of 55yards, and perfect shooting:

68.2% of the shots will be within 1/4" vertical spread (1s)
95.5% of the shots will be within 1/2" vertical spread (2s)
99.7% of the shots will be within 3/4" vertical spread (3s)

Assuming the barrel is capable of 1moa, most every miss will be my fault (mis-range or mis-read wind). A smaller SD gives me more leeway for error.

[Miguel]

I finally went to Hawke website and get the Chairgun pro, which is free, and now I have a ton of features, the only problem is understand all of them :-)
I have just converted my hammerli 850 to hpa and I was absolutely amazed.
With JSB 8.44 over 56 good shots betwen 960 and 928 fps, spread 32 SD 6.503 and with AA heavies 40 good shots (and I had to go back home) betwen 893 and 881, spread 12, SD 2.776.
I guess that I should short the first sesion to 40 which gives me way more consistency.
Any way,
Thank you all for your help, the learning process continues.
Best

[WIanB]

As promised - hope you find it useful.

[Miguel]

Thank you very much WIanB,
I´m certain that will be very helpfull.
Best.