Short but sweet (spot)

Vinnyp

Vinnyp

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Evening folks 😀

As I’m sure some of you are well aware I’m once again dipping my toe into the fascinating world of pcp air rifles. (My first was a pr900)

After much testing chronographing etc I think I’ve found the “sweet spot” as it’s known in the un-regulated ultra clx…….🤔

Problem is I don’t know why it’s where it is, whether it’s acceptable or not etc etc…….

I wrote down the last chrono test (apologies for the handwriting) to try to get a better understanding and took a picture to share with the more knowledgeable good folks of the agf………….

Picture of results……………
1B7A59C8-8522-47AF-AC14-ACD7D718A2E5.webp


I started at 200bar as I quickly realised although you can fill the clx to 232bar the power is very low (sub 9.5ftlb) and steadily rises, why that is I don’t know 🤔

From these results I’m saying the “sweet spot” is 180-90bar (48shots/4xmags) with a spread of 20 fps across those 48 shots.

This seems a little low to me and I’m struggling to fathom why you can fill to 232bar when 180-90bar is the most consistent (and accurate) 🤔

BSA say the clx in .22 is capable of 72 shots! It is but the extreme spread and poi shift is a joke!

If anyone could shed some light on this for me in very simple complete beginner terms that would be great 😀

👍🏻
 
Unregulated PCPs have a peak power level that usually doesn't coincide with the peak cylinder pressure because the high pressure acts to force the valve shut upon firing, once you drop the pressure slightly there's less pressure acting on the valve so it can let more air through, increasing the power.

My unregulated MMC Ultra's (.177) sweet spot was 175-100 bar but only gave 25 or so decent shots, it's closer to 50 now I can take advantage of the 232 bar fill pressure whilst still staying consistent due to the reg.

It helps to create a graph of the FPS/shot count, you can visualize the sweet spot much easier. I had a half decent thread on the old AGF regarding doing this - I will see if I can recover it.
 
mattyts said:
Unregulated PCPs have a peak power level that usually doesn't coincide with the peak cylinder pressure because the high pressure acts to force the valve shut upon firing, once you drop the pressure slightly there's less pressure acting on the valve so it can let more air through, increasing the power.

My unregulated MMC Ultra's (.177) sweet spot was 175-100 bar but only gave 25 or so decent shots, it's closer to 50 now I can take advantage of the 232 bar fill pressure whilst still staying consistent due to the reg.

It helps to create a graph of the FPS/shot count, you can visualize the sweet spot much easier. I had a half decent thread on the old AGF regarding doing this - I will see if I can recover it.
Click to expand...

Thankyou 👍🏻

So should I be impressed with my findings then?, 48 shots un-regulated but a 20fps spread 🤔

I imagine your 50 regulated shots are a lot closer together in the fps department?
 
Vinnyp said:
Thankyou 👍🏻

So should I be impressed with my findings then?, 48 shots un-regulated but a 20fps spread 🤔

I imagine your 50 regulated shots are a lot closer together in the fps department?
Click to expand...

I would say your sweet spot is from shot 19 to the end of your recordings, that would give 41 shots with a max 4 FPS shot to shot variation & a max spread of 14 FPS across the whole string, perfectly acceptable for an unregged Ultra I recon.

I don't think I've any data stored anymore regarding a shot string through my Ultra but it was 1-2 FPS between shots and 8 or 9 FPS across the whole string from memory, but the increased useable shot count was the biggest thing I gained from having it done - well worth the money.
 
mattyts said:
I would say your sweet spot is from shot 19 to the end of your recordings, that would give 41 shots with a max 4 FPS shot to shot variation & a max spread of 14 FPS across the whole string, perfectly acceptable for an unregged Ultra I recon.

I don't think I've any data stored anymore regarding a shot string through my Ultra but it was 1-2 FPS between shots and 8 or 9 FPS across the whole string from memory, but the increased useable shot count was the biggest thing I gained from having it done - well worth the money.
Click to expand...

Now I’m wondering then if 180bar is still too high? Also I’ve never taken it below 90bar, would it be possible that it may just keep going 🤔

I think more testing is required here 😫
 
Vinnyp said:
Now I’m wondering then if 180bar is still too high? Also I’ve never taken it below 90bar, would it be possible that it may just keep going 🤔

I think more testing is required here 😫
Click to expand...

Fill it to 200 bar & dry fire it 18 times, put it back on the bottle (don't go off the gauge on the gun if it has one, they're not accurate enough for working sweet spots out) and see what pressure it reads - that would be my filling pressure from your string above.

It's all personal preference in the end, some people are happy to sacrifice the FPS spread and bump the gap up more if they get another 5 or 10 shots, some people aren't.

Standard deviation is something to keep in mind when working the sweet spots out, but that's a lot more involved sums wise than just circling a group of shots on a graph or a string.
 
mattyts said:
Fill it to 200 bar & dry fire it 18 times, put it back on the bottle (don't go off the gauge on the gun if it has one, they're not accurate enough for working sweet spots out) and see what pressure it reads - that would be my filling pressure from your string above.

It's all personal preference in the end, some people are happy to sacrifice the FPS spread and bump the gap up more if they get another 5 or 10 shots, some people aren't.

Standard deviation is something to keep in mind when working the sweet spots out, but that's a lot more involved sums wise than just circling a group of shots on a graph or a string.
Click to expand...

Thankyou I will try that next 👍🏻

I’ll get my head around it all eventually 😂👍🏻
 
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