Tuning A Tuning Curiosity

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Drumsnguns

Member
Jun 14, 2016
959
19
North Carolina, United States
I have an Impact MK2 with PP/700 mm Superior Heavy/ Huma Dual TP/ FX pin Probe and the 57 mm HS. (not using the power kit...only the pin probe).

I'm tuning for 980 fps+ with NSA 33.5. In order to get there I am at 130 Bar on the reg. and have the HSTA almost all the way in. I settled on 995 at MAX and tuned down the HTSA a bit just until I just see the velocity drop. I'll use the power wheel to get me to the setting where I get the best groups....which on my gun is usually 4.

I'm wondering what reg pressures others are getting with a similar setup and speed?

Reason I ask is I have heard of a similar set up achieving 1000 fps with only 115 Bar! The difference is they are using the Power kit with (I assume) the 52 mm HS and the Nielsen Pin Probe.

This has caused me to cock at least one eyebrow.

Not calling anybody out but if he's getting that then more power to him and I wonder where I might be going wrong...and yes I do realize all guns are different.

Cheers.
 
I've found similar results, the only difference is I have the Slug A liner and use the lighter valve spring from the Slug Power kit. I too cock an eyebrow about getting 1000 FPS with the NSA 34 grain at 110 or 115 bar (if no hammer weights). Maybe their gauge is off by 15 or 20 bar, that would not be unusual. The only thing I can think of is if they used the two washers (hammer weights) that the reg pressure could be reduced by 10 to 15 bar. I ended up on MAX with no slop in the HST adjust, reg. at 135 bar, light valve spring (two lines), Ernest dual transfer port, no hammer weight, stock 52mm hammer spring, FX Power Plenum, 700mm Slug A liner shooting the NSA 43.5 grain at 895 FPS. Super accurate out to 175 yards, haven't gone farther.
 
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Centercut

I got to thinking about it and it dawned on me that he might be using the power kit’s lighter valve spring. I bought the power kit just to get the pin probe but decided to try the included valve spring. It proved too powerful so I took it out. I could hardly get it to come down at the settings I had. It was shooting well over 1000 FPS. 
Now I’m thinking that using that lighter spring w the 57 mm HS could indeed get me to 1000 FPS at a much lower reg setting. 


I’m curious but I finally found a setting that is giving me 0.273” and 0.405” groups at 62 yards. I really think I can’t do much better than that and after all of the air and slugs I went through to get there.... I think I can be happy with that. ....... for while😉😉😉

...and the weather is total s%#! right now. I’m shooting at night and early morning w flashlights when the rain lets up and winds are calm. Would rather shoot than tune when I get those fleeting opportunities

Been reading some of your posts lately. Super impressed with your results. I might have to try that sometime. 
Best

KP
 
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Agree, if you use that light valve spring at lower power levels (under 70 FPE), it will be very hard to get a reasonable ES. If I was shooting 34 grain slugs at 950 to 970 FPS, I would use the stock valve spring for consistent shot velocity. I didn't even use the hammer weights to get to 80 FPE with my .25 Impact. I did use the pin probe and dual transfer port, but stock hammer spring and no weight. I could go higher with the hammer weights, but why? The gun just gets harder to shoot, uses more air, and has no reasonable benefit. 80 FPE with a .25 slug is pretty good and the gun is very accurate.
 
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Interesting. When I first bought the MK2 I had trouble getting past 900 FPS. No amount of reg pressure could get me higher but of course I was shooting out of the box with standard HS and FX TP and pellet probe. The 57 mm allowed me to move higher in velocity. And at the time the Power Kit had not been released.
I’ll stay where I am for a while. I’m tired and going broke tuning but I’m Interested in the 43 gn slugs. I have a sample pack of them. Might try them next good weather day which should only be in two weeks here in NC 🙄🙄

Appreciate your input and knowledge, Centercut. 
Best

KP
 
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