Impact MK11 with power plenum 700mm .25cal. Low Power

[hotair]

Hello fellow shooters,

It seems these guns are very different as far as power output, (velocity), is concerned. All velocities were made with all the slack taken out of the hammer adjuster and the power wheel is on max. With the stock parts the reg. tops out at 120 bars. Anything over that doesn't increase velocity and after about 125-130 bars the velocity goes down. The velocity with the jsb 34 gr. tops out at 923 fps. I was informed by FXUSA that by changing the hammer spring and valve spring the gun should shoot the 34gr. up to around 1000 fps.The hammer spring was then changed from 52 to 57mm and a lighter valve spring was installed. The gun shot exactly the same like nothing was done. Not knowing for sure how far the valve was opening I did the following. A .200" stop was made out of delrin and placed in the valve adjuster cap. The cap was then screwed in until the stop made contact with the end of the valve rod. I continued to turn the cap until the valve was completely closed. Then a measurement was taken from the end of the cap to the shoulder of valve adjuster housing. Then I unscrewed the cap .100",.150", and .200''. I then put in a very lite valve spring. The purpose of all this was to make sure the valve was opening and how far. Each setting was tested at 120, 130, and 140 bars. I could see that the end of the valve rod was touching my delrin stop so I knew that the valve was opening to whatever I had it set at. After all that the reg. toped out at 130 bars and the velocity was at 943 fps. More than 130 bars and the velocity goes down. I've spoken to Ernest about this and he was able to get 1000 fps from a stock Impact MK11 .25 cal. w/pp by changing the two springs and setting the reg. around 155 - 160 bars. All the measurements that he asked me to take are what they're suposed to be. We are lost at this point on why this gun won't generate high power. Has anyone out there had a Impact in .25 cal. that started out with low power and was able to make the necessary changes to get the power up? The gun was bought specifically to shoot the heavier pellets/slugs between 900 - 1000 fps. I been told that the superior liners will be back in stock very soon. The gun has the stock pellet STX liner. The goal is to try out several slugs at velocities over 900 fps. I've done some testing with a RAW HM1000X poly under 900 fps with poor results. I know shooting slugs in .25 cal. is tough if you want 1 moa at 100yds. All one can do is try. Thank you.



















in the velocity

 

[Hanz]

I'm new to PCPs and just received an Impact MkII PP in .25 with the 700MM barrel from Utah Airguns. I asked them to tune it to shoot the JSB King Heavy Diablo 33.95gr pellets (Thinking I would shoot NSA 36.2 slugs on the same tune). The card from Utah says 940fps average. I haven't verified that but have no reason to doubt them. They made no mention of changing parts.

I have no knowledge of tuning so I'm really just here stating how my rifle arrived. I don't know if they could have gotten more velocity but I'm happy with the 940 fps they gave me.

I hope this helps somehow but realize it may not.

 

[ImpactX]

130 bar for 930fps is normal. How is that low? I was thinking you getting like 500fps or something. I also have the impact with PP 25 cal and mine is shooting 950 fps on average, highest around 960fps but that is with 140 bar and drill larger brass TP and larger pellet prob. This your stock in at 930fps with 130bar is normal. Those guys getting over 1000 fps with the heavy mk2 have modified their guns to shoot max power. Do not expect your gun to shoot the same speed. And why would you need to go over 1000fps just cause 1 dude modify his to shoot 1000fps. Mk2 heavy are more accurate at 830 to 860 fps.

 

[hotair]

Too bad you don't know what they did. I got my gun there also. I've spoken to Josh at Utah who is the main tuner and on some of the guns he was only able to get 925-930 fps. He probably didn't change any parts but it would be good to know just what he did. Your gun should shoot very well at that velocity contrary to what some people may think, which is--the velocity is too high. One inch groups at 100 yds. should be very do able without wind.

 

[hotair]

Dear Impactx,

As already stated these guns are very different when it comes to power. The 1000 fps was a reference number. I normally shoot the 34's at 905 fps with 1 moa accuracy at 100yds without wind. The "dude" that you are referring to is Ernest Rowe who is the head technican at FXUSA and probably knows more about fx guns than the factory. I spoke to him on the phone about the gun that he got 1000 fps with. It was a stock Impact MK11 .25 cal. 700 mm with the power plenum. The only mod was changing the springs--nothing else. The reg. was set at 160 bar. Some of these guns will get 960-975 fps with the reg. set at 135 -140 bars. With my gun anything higher than 120 bars with the stock springs or the mod springs and the velocity starts to go down and that's with the 57mm hammer spring and all the play taken out of the adjuster. The fact that there was no change in velocity when the springs were changed says there is something else holding up the power level.

 

[bigHUN]

When I got my Impact PP in March I did retune the stock brand new gun several times as a learning curve and I had a max of 976.1 but with aggressive deviation in speed and unnecessary air loss. JSB King Heavy 33.95 gr I am talking about, 700mm in 25 cal.

I tighten up the ES @ about 911 but the gun is still very laud and blows the dust in front of the muzzle 1.5 meter away. Here in Canada we don't have any kind of silencers and even the compensator is not vented inside shroud, only way I can strip of the big air blast installing a muzzle break but that again doesn't fit a gun in the case.

So this is a side effect, my observation playing with 900+ speeds but also I have to admit I did not got to slugs yet because all ranges still closed at my place and to build back up all the membership privileges again most likely a next 6-8 months waiting inline.