Helpful tuning tips and links

[bear air]

Would this one be too much hammer spring?

[PoolDoc]

Looks like it has a bell curve of sorts. regulation issue?

[oldpro]

 Both good guesses but still not it and it’s a non regulated string.

[mobilehomer]

I ain't the sharpest knife in the drawer when it comes to reading strings, but it seems like the hammer is sticking a little. There is a lot of variance shot to shot.

[oldpro]

 Another good guess but it’s not a mechanical problem. Very common with High power tuning.

[PoolDoc]

Hmmm I hate problem children lol
Pressure too low for given fpe?

[oldpro]

Hmmm I hate problem children lol
Pressure too low for given fpe?

Not that. Hint, think what mods are common with high power tunes.

[Dairyboy]

Too heavy of a hammer? I'm not sure. But if it were my gun I'd just turn hammer spring in alittle to get the first shot to start at 920ish fps lol

[PoolDoc]

Since I dislike "problem children" and also mechanical mysteries Ill keep guessing
Porting over sized?

[oldpro]

Since I dislike "problem children" and also mechanical mysteries Ill keep guessing
Porting over sized?

There ya go! The Transfer port is too large in this case. The valve in this gun has its peak velocity at around 2600 psi so when the valve gets to that point and the big transfer port is not restricting the flow it starts really shooting fast till the pressure drops this sort of over porting will also cause very poor ES/Sd across the board. To fix this you would either tune it for a declining string for hunting or put in a smaller transfer port to slow the flow in the middle power band area and smooth out the string. Very common issue with those seeking Power in their PCP guns.   

[oldpro]

Here’s another one what do you think the problem is
 

Created: 10/16/14 10:10 AM
Description: WAR .25 carbine
Notes 1: 6 turns HT 3 turns HS
Notes 2:
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 25.39
Temp: 61 °F
BP: 30.06 inHg
Altitude: 0.00
#          FPS   FT-LBS       PF
16    844      40.17    21.43   
15    851      40.84    21.61   
14    861      41.80    21.86   
13    863      42.00    21.91   
12    865      42.19    21.96   
11    872      42.88    22.14   
10    871      42.78    22.11   
9     872      42.88    22.14   
8     873      42.97    22.17   
7     867      42.39    22.01   
6     864      42.09    21.94   
5     875      43.17    22.22   
4     870      42.68    22.09   
3     846      40.36    21.48   
2     860      41.70    21.84   
1     850      40.74    21.58   
Average: 862.8 FPS
SD: 10.0 FPS
Min: 844 FPS
Max: 875 FPS
Spread: 31 FPS
Shot/sec: 0.1
True MV: 863 FPS
Group Size (in): 0.00

[bear air]

Too much HT?

[oldpro]

Too much HT?

No Sir. Hint This is a mechanical problem

[Jacob_M]

This is a war .25 carbine so I’m assuming the gun has a bottle on it. To only get that many shots and Have such a short bell curve, the valve is probably over dwelling.

Or if the gun has a small air cylinder. It doesn’t look like a bad string lol.

[PoolDoc]

Hmmm this is fun...
sticky hammer or greased hammer?

[oldpro]

Hmmm this is fun...
sticky hammer or greased hammer?

This is not a full string I chopped it short due to the issue.Not a hammer issue. This is fun I could do this for months I have 1100 saved strings LOL!!!!

[PoolDoc]

Im no expert lol but I don't give up easy haha.
How about pellets not being seated past transfer port?

[oldpro]

Im no expert lol but I don't give up easy haha.
How about pellets not being seated past transfer port?

Ow thats a good one and I have a string of that also but not the case here.

[Jacob_M]

Not consistent pressure from the regulator.

[bear air]

Is the hammer hanging up on the sear? This is fun and I'm learning a lot. This is tuning 101!