Bit of a head-scratcher, here

[Drumsnguns]

So, as I wait for my 700 mm barrel/slug liner to come back from warranty at FX..(its been there 3 weeks and not even in the queue yet ), I have taken my 600 mm barrel and pellet liner off my gen 1 Impact and put it on my Gen2.

I had tuned it to 880 fps w JSB MKII 34 gn and though it was pretty good, it wasn't where I know it could be.

After some reading I decided that it was perhaps going too fast so retuned down from 120 bar to 100 bar and re-adjusted the HSTA and put the valve at 4 lines.The plan was to turn the valve in and to bring it down to 840 at max on the PW

I shot targets at 60 m and 89 m (far as I could go) and was like "Meh"

So on a whim re-shot at PW 3; PW 4; PW 5 and Max.

Some interesting results:

PW 3: 829 fps.....0.959" ctc

PW 4: 846 fps....0.730" ctc

PW 5: 843 fps.....0.287" ctc

PW Max: 849 fps...1.122 ctc

So all of this to get to my question ( I have a biology background so I get long-winded with details...sorry, it's a curse)...

Shouldn't my velocities be a bit further spread apart on the PW?

It indicates that the HSTA might be too far in (strong) but thought I had backed the HSTA back out far enough to get a good tune for the 100 Bar setting. I do have the 57 mm HS in for slugs so maybe it's still too far in for the reg setting.

But, My targets at PW 5 are so good, I'm tempted to just leave things 'wrong" haha.

Would anyone, who actually knows what they are doing, like to leave a comment? I could use a little guidance.

Thanks and Happy Memorial Day

 4 shots ea (conserving air)

 5 shots, three in one hole

 

[Vetmx]

Before guys start chiming in, some more data please. Are the groups at PW5 repeatable? Or is that just one shooting session. 

 

[Drumsnguns]

 The 4 groups were shot in the morning and then when the wind died down, I shot the 89 Meter, PW 5 group in the evening right before sunset when the winds calmed.

I plan to get back out today and try to repeat. Winds are good, but can't say the same for my air supply. Plenty though to try to repeat a few times more, so stand by.

Oh and I forgot ....shooting straight out of the tin...no weighing or sorting.

 

[sonny]

I shoot my Impact orig S/T barrel (600mm) @ 910 with 34gr kings, 1/2 inch 5 shot groups at 60 yards consistently. 

 

[stoti]

Your best group and worst group are separated by only 6fps. That's not much at all to make that kind of difference in accuracy. Most air guns have a higher ES than that. I'd start your testing at like 30-40yds to make sure your results are caused by changes to the settings and not you. 60 meters and 88meters are a long way to be shooting when tuning an air gun.

Good luck. Stoti

 

[elh0102]

I can't answer your question regarding the rifle's adjustments, but I'll offer this observation. I think you are trying to draw conclusions from a way too small sample, and, as mentioned above, you're shooting too far for general tuning. 

 

[Drumsnguns]

Posting my shoot from today. And as it would have it, what happens on Day 1 won't necessarily happen on Day 2. So with that, I shot again at 60 M, (sorry Stoti, didn't see your post until after the fact), and there were some slight differences.

Now PW Max is the tightest group.

PW 5 not as good though when I did a 3 shot sighter group on another target, it was all 3 in one. 

The wind did pick up some and the target was moving a bit from time to time.

I guess my big question is why not much of a spread between PW settings? I expect something more like 10-15 fps between say 3-4 or 4-5.

Chrony results as I shot targets.....

PW 3: 828 FPS; ES 11; SD 8

PW 4 834 FPS; ES 9; SD 2

PW 5 839 FPS; ES 9; SD 3

PW 6 841 FPS; ES 6; SD 2

I'm not unhappy with the results here but if I'm doing something wrong then I'd be happy w more input.

I will come in closer to 30 yards and shoot a few more targets; maybe around late evening when winds are calmer.. Thanks for the input so far guys

 

[sonny]

i would suggest increasing reg pressure to about 130 bar bring up your speed to around 930-940with h/s then drop your v/s to bring speed down to 900- 910 and remember the mini gauges are usually off a few bar.

 

[Drumsnguns]

Sonny, so you're getting great groups with the non-liner ST barrel? Man that's fantastic. I still have my original barrel. Would be interesting to see what mine does. Ernest enlarged the TP port on is so I'm sure it will be shooting hotter at my current settings. 

Thanks for throwing that out there.

 

[Drumsnguns]

One thing I like with the lower setting is air conservation. And the accuracy is the best I've gotten. I'll stay here for a while. I was at 120 for 880 fps with the valve on 3.5 lines and it was good but not consistent and really not all THAT good.

When I get more air I might record settings then try some other stuff. Hard getting hooked up with paintball shop's Covid hours right now. They close before I get off work. Snd not open on the weekends yet.

 

[sonny]

I have heard from others the pellet liners were not as good but the new superior liners I haven't heard anything negative. maybe they shoot slugs better?

 

[Drumsnguns]

Glad I named this the big head scratcher because its spot on.

I shot more targets at 30 as some suggested I do. And I repeated several times and it was quite consistent. Now PW 3 is the tightest. Hmmmm what does this tell me? Absolutely nothing.

Am I tuning wrong??? This is how I tune:

Open valve to to 4 lines

Pick a target velocity for said pellet...what this magical velocity is? ....I haven't a clue and probably a lot of other people don't either. As far as I know MKII 34 gn does well between 800 and 900 fps and then there's guys tuning Impact MK2 w power plenum up to 965 fps for JSB MKII....so who knows???

So I choose 880 fps....sounds like a good speed, right?

Then I slowly bring up the reg and adjust the HSTA to the max V and if still too low then I bring the reg up some more, adjustiing HTSA as I go along until I'm about 15 fps OVER my target. 

Then finally I turn in the Valve until I get to 880 fps and hope all is Good. 

At the end I'm shooting at PW Max.

One thing I notice with shooting on PW 3 today is the gun is quiet and vibration is minimal. When I shoot at PW Max things get clanky and loud and I'm sure a bad vibration is set up.

If I'm doing something wrong please chime in. otherwise I guess I'll be hanging around PW 3 until it all changes tomorrow...

 

[stoti]

If you like the way the shot cycle feels when you're shooting on power wheel number three, then leave it. You can't complain about that accuracy, .245", .330" and .339" are awesome! You know the gun is shooting accurately as it is, now you can shoot longer groups, fine tune with the valve adjuster, leave it or whatever you want. Great job man!

Stoti 

 

[Drumsnguns]

Appreciate the input/ Thanks Stoti and others. It really is shooting great right now.



KP

 

[Rj]

Thanks for the data. Always nice to see it on paper. As to your first question, the 57 mm spring is longer, but the shorter one is stronger. Measured by a member here on the forum with digital scale. If you want more spread between power wheel settings, I would put the other spring in and go from there. I think you'll have better results finding that relaxed shot cycle in a more linear fashion. 

 

[Drumsnguns]

Thanks Rj

This gun is going to be a dedicated slug gun which is why I put the 57 mm spring in. I couldn't get past the very low 900's with the shorter spring for slugs. My slug liner is at FX right now as I was having accuracy issues with it and my gen 1 impact is suffering from a serious air leak so I'm just using the barrel/liner from the gen.1 while I wait for the 700 mm to come back.

So I won't be swapping out the 57 mm on this particular gun.

I'm not sure what is in the gen 1 but I'm going to tear it down so I'll measure it.

Interesting info on the strength of the springs and how they work with the power wheel. Thanks for that.