Helpful tuning tips and links

[oldpro]

 So we’ve seen some pretty bad strings and odd ones but how about a really good one and what separates it from a decent string. There’s more to a good string than just the ES let’s get into the basics. So the number one goal for most shooters is to have and accurate gun regardless if the shooter is a hunter or bench rest shooter so to achieve this there are a few things that need to be achieved in the shot string to make this happen. For most people they use the ES or extreme spread this is determined by the fastest shot subtracted by the slowest shot in a shot string. The primary goal is to have a single digit ES when possible when tuning as this will yield the best performance from shot to shot. Now another useful tool is the ES as a percentage and as a percentage you want it under 2% if possible this also is a goal for tuning to get the best possible shot to shot consistency so to get the ES percentage you take the ES divide it by the fastest shot then times it by 100. The last but not least is the SD or standard deviation this is the difference in speed shot to shot it’s not the easiest to quickly figure out that’s why most people use ES or the ES percentage but most chronographs will display the SD but if you want to figure it out on paper here’s a good link.
https://www.mathsisfun.com/data/standard-deviation-formulas.html
 So below I’ll post a good string then we will go over it using the above tools.

[oldpro]

Created: 12/21/18 03:56 PM
Description: python valve test
Notes 1: 3000-1825
Notes 2: jSB beast diablo
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 16.00
Temp: 44 °F
BP: 30.23 inHg
Altitude: 0.00
#          FPS   FT-LBS       PF
49    799      22.68    12.78   
48    800      22.74    12.80   
47    799      22.68    12.78   
46    800      22.74    12.80   
45    799      22.68    12.78   
44    801      22.80    12.82   
43    802      22.86    12.83   
42    801      22.80    12.82   
41    799      22.68    12.78   
40    801      22.80    12.82   
39    799      22.68    12.78   
38    801      22.80    12.82   
37    802      22.86    12.83   
36    799      22.68    12.78   
35    798      22.63    12.77   
34    800      22.74    12.80   
33    801      22.80    12.82   
32    801      22.80    12.82   
31    800      22.74    12.80   
30    800      22.74    12.80   
29    801      22.80    12.82   
28    798      22.63    12.77   
27    802      22.86    12.83   
26    801      22.80    12.82   
25    801      22.80    12.82   
24    798      22.63    12.77   
23    799      22.68    12.78   
22    799      22.68    12.78   
21    802      22.86    12.83   
20    803      22.91    12.85   
19    799      22.68    12.78   
18    800      22.74    12.80   
17    804      22.97    12.86   
16    799      22.68    12.78   
15    799      22.68    12.78   
14    801      22.80    12.82   
13    801      22.80    12.82   
12    798      22.63    12.77   
11    801      22.80    12.82   
10    798      22.63    12.77   
9     799      22.68    12.78   
8     800      22.74    12.80   
7     801      22.80    12.82   
6     799      22.68    12.78   
5     799      22.68    12.78   
4     799      22.68    12.78   
3     798      22.63    12.77   
2     802      22.86    12.83   
1     802      22.86    12.83   
Average: 800.1 FPS
SD: 1.4 FPS
Min: 798 FPS
Max: 804 FPS
Spread: 6 FPS
Shot/sec: 0.1
True MV: 800 FPS
Group Size (in): 0.00
 So using this above string let’s look into what makes it desirable as a shooter. First our goal is to have a single digit ES when possible and we do it’s only 6 so mission number one check two we want a ES percentage under 2% so lets check it 6/804x100= .74 or .74% ES that’s very good check box 2 our third goal is the SD remember we want a single digit SD when possible and ours is a outstanding 1.4 check 3.
 So to bring it all together to be accurate you need both shot to shot consistently (SD) and consistency over the entire shot string (ES) these two things together will give you the best advantage at hitting your target which is always the primary goal when shooting at something.

[bear air]

Travis, thank you for creating a thread like this. I'm finding it to be very helpful when it comes to tuning. Do you have a set parameter when it comes to ES? For instance if it is over X amount you take it back to the tuning table and retune it and lower the ES? I know the goal is to get the gun to shoot as consistently as possible but when does it become unacceptable for you?

[oldpro]

Travis, thank you for creating a thread like this. I'm finding it to be very helpful when it comes to tuning. Do you have a set parameter when it comes to ES? For instance if it is over X amount you take it back to the tuning table and retune it and lower the ES? I know the goal is to get the gun to shoot as consistently as possible but when does it become unacceptable for you?

I use a single digit over the entire shot string as my goal it’s not always possible but it’s the goal. So if I have to fill higher or stop shooting lower in the fill to get my single digit that’s what I do. It’s all determined by what the gun does from the first to the last shot to get it to that single digit ES

[bear air]

That makes sense. Thanks Travis.

[oldpro]

That makes sense. Thanks Travis.

Your Welcome!

[oldpro]

 OK Test time!!!
 Here’s a string that needs help! You’ve read threw(hopefully) some of the tuning guide and have and idea what to do so now let’s all work together and fix this gun. There’s several ways to fix this so I’ll give you my version after I hear your thoughts.
Created: 10/06/17 11:07 AM
Description:
Notes 1:
Notes 2:
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 0.00
Temp: 64 °F
BP: 30.26 inHg
Altitude: 0.00
#          FPS   FT-LBS       PF
25    690      0.00     0.00   
24    715      0.00     0.00   
23    718      0.00     0.00   
22    729      0.00     0.00   
21    725      0.00     0.00   
20    748      0.00     0.00   
19    756      0.00     0.00   
18    754      0.00     0.00   
17    756      0.00     0.00   
16    763      0.00     0.00   
15    757      0.00     0.00   
14    754      0.00     0.00   
13    747      0.00     0.00   
12    747      0.00     0.00   
11    741      0.00     0.00   
10    732      0.00     0.00   
9     723      0.00     0.00   
8     719      0.00     0.00   
7     713      0.00     0.00   
6     709      0.00     0.00   
5     709      0.00     0.00   
4     700      0.00     0.00   
3     693      0.00     0.00   
2     682      0.00     0.00   
1     671      0.00     0.00   
Average: 726.0 FPS
SD: 26.1 FPS
Min: 671 FPS
Max: 763 FPS
Spread: 92 FPS
Shot/sec: 0.1
True MV: 726 FPS
Group Size (in): 0.00

[triggertreat]

Increase HS or lower fill pressure.

[PoolDoc]

Thanks for this.
1) increase hammer spring tension to cause a "cliff" shot string? or
2) restrict transfer port size?

[RDB]

What gun? Hammer throw adjustments? What are we working with?

I agree with Pool, choke the t port to flatten it out, add a buffer and lean on the hammer spring a little more.But there's more than one way to skin a cat.

[oldpro]

 Good work guys! I strangled the TP and lowered the fill pressure 100 psi then adjusted the hammer strike to accommodate the changes

[Bigragu]

Just read thru this entire thread. Thank you, Travis, and looking at the time of your last post, you better hit the sack, lol. It’s almost midnight and you’re holding Airgun tuning class!

[Hawkeye51]

Why isn't this pinned in the PCP forum?

Great general info, would be a good sticky!

[Madd Hatter]

Bump for those who haven't had the chance to read this thread. Lots and lots of good info.

[oldpro]

Bump for those who haven't had the chance to read this thread. Lots and lots of good info.

Thanks Robert! I totally forgot about this!!! Ill throw some current info in this week.

[avator]

Well, there's 45 minutes I'll never get back...
I wanted to take a stab at every one of them but I don't have a time machine.... 

Thanks Travis, good info.

BTW.... did Jason ever get to punch you?

[bear air]

I enjoyed this thread a lot when it was going. Hopefully you got some time to continue on with it Travis.

[oldpro]

I enjoyed this thread a lot when it was going. Hopefully you got some time to continue on with it Travis.

To be honest I forgot about it. I’ll tally on. Would you like some short videos also?

[bear air]

That'd be awesome. These scenarios help out a lot to learning how to diagnose problems and how to fix them.

[oldpro]

That'd be awesome. These scenarios help out a lot to learning how to diagnose problems and how to fix them.

Thats awesome Chris. Im working on a few things to post