Fx Impact Fix & Mods for more FPS / FPE

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Hey guys! 

Sorry, I know the thread is old.

Was just wondering what gives;

I have a relatively New Impact X in 25 caliber, 700 millimeter Barrel. It came from the factory set on 150 bar, there is no slack in the hammer spring side piece to adjust out, and on max I'm only getting 835 feet per second with the regular jsb King 2 6 grain. I was sure hoping it would be more like 900.

Now mind you, it shoots a ragged hole with three different pellets, the jsb, the jsb heavy, and poly. mags.
 
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Hey guys! 

Sorry, I know the thread is old.

Was just wondering what gives;

I have a relatively New Impact X in 25 caliber, 700 millimeter Barrel. It came from the factory set on 150 bar, there is no slack in the hammer spring side piece to adjust out, and on max I'm only getting 835 feet per second with the regular jsb King 2 6 grain. I was sure hoping it would be more like 900.

Now mind you, it shoots a ragged hole with three different pellets, the jsb, the jsb heavy, and poly. mags.
Click to expand...

Turn it down to 135 and work your way up a couple / few bar at a time and see where the velocity starts to decrease. You'll hit a point where the hammer cannot open the valve all the way, identify the pressure at that point and that is the max pressure that you can use without a (brass) hammer weight or modified hammer system.
 
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Hi again gents!

I did try the recommendations y'all gave me of dropping my reg from 150 to 1:35 ish. Velocity only dropped more from 835 2 around 8:10.

Reminder, this being in 25 caliber with regular jsb King 27 grain. I finally decided my gauge must be reading very high, after seeing the video about the adjustment screw being flushed at its limits. Mine was steel recessed. I adjusted it slightly where I'm reading 1:56 or so. Then I threaded the valve bumper outward to the fourth line. Was too dark to read the chronograph, but there was a noticeable increase in velocity just by sense. I was wondering if I just got a really weak tune, or build for that matter. Thank you all for your help
 
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Hi again gents!

I did try the recommendations y'all gave me of dropping my reg from 150 to 1:35 ish. Velocity only dropped more from 835 2 around 8:10.

Reminder, this being in 25 caliber with regular jsb King 27 grain. I finally decided my gauge must be reading very high, after seeing the video about the adjustment screw being flushed at its limits. Mine was steel recessed. I adjusted it slightly where I'm reading 1:56 or so. Then I threaded the valve bumper outward to the fourth line. Was too dark to read the chronograph, but there was a noticeable increase in velocity just by sense. I was wondering if I just got a really weak tune, or build for that matter. Thank you all for your help
Click to expand...

You'd still want to find out at what point your velocity drops off by starting at a low pressure > shooting over a chrono > raising pressure a few bars > recording the speed > repeating until the climbing velocity begins to drop. It may be that the fastest velocity that your rifle is capable of is lower than where you think it is (regardless of what the dial reads).
 
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Yes, I understand fully the principles of valve lock and how its encountered. I'm saying that velocity dropped when going from 150 bar down to 135, and gained when the gauge read 156. That's why I was wondering why I seemed so weak, because I know it's not into valve lock at 150 bar.

If I seem to still be missing something, I do wanna listen to ideas.

Thanks, guys!
 
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@2fast2furious I read about your jamming, I shoot with both mags and no problems...it might be that you remove too much O?, if you check my pic, mine has "flaps" and you remove that ... check this one, all in 0.25 that I made a few months ago:

1571222441_3661734655da6f3a9665278.24661043_pic.png


0.25 cal O removal on PP and enlargement and countersink on BP

That is how I do it, maybe you took too much O and that is pushing the slug down and you get your jamming. Donno, is something never happend to me (but is key to understand where is the problem). You need to figure why is jamming, could be the brass tp? (I shoot mainly slugs in all cals for hunting and never got a problem with jamming). PP are cheap and you can get those easy FX. BTW is mentioned several times, as an advice: Get the parts before making any mods, so you can go back in case you are not ok with your change.

Click to expand...

Hi there, I’m about to begin with the modifications on my FX Impact X, I have already collected all the parts that I need to proceed, and have almost all the tooling ready to began with this project. Only question that I have (maybe a lot more will come for sure) is what sort of dremel bits are you using to perform the elongated brass port. I have several bits meant to be used for that purpose but so many different shapes and I’m not quite sure which one would work best. If you could share with us an picture of the recommended bits for grinding the brass port, it would be highly appreciated.

Gracias de antemano Eduardo


 
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I do this work with a li-ion rotary tool and a carbide burr, second one from the right in pic ⑲. Single cut burrs are for non ferrous metals while the double cuts are for ferrous.

Polish the area last using a felt tip and red polishing compound.

Use low to medium speed when removing metal for best control. Light pressure and a tight grip. Polish at high speed.

1572045775_9393476105db383cf3e8b71.27592898_1566849471_231067135d6439bf5cb1d1.45688243_61BMycI...jpg
1570814052_3612213255da0b86475d435.16036272_Port1 - (2).jpg
1570814052_18948973155da0b864a24ad3.38412677_Port2 -.jpg

 
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@2fast2furious I read about your jamming, I shoot with both mags and no problems...it might be that you remove too much O?, if you check my pic, mine has "flaps" and you remove that ... check this one, all in 0.25 that I made a few months ago:

1571222441_3661734655da6f3a9665278.24661043_pic.png


0.25 cal O removal on PP and enlargement and countersink on BP

That is how I do it, maybe you took too much O and that is pushing the slug down and you get your jamming. Donno, is something never happend to me (but is key to understand where is the problem). You need to figure why is jamming, could be the brass tp? (I shoot mainly slugs in all cals for hunting and never got a problem with jamming). PP are cheap and you can get those easy FX. BTW is mentioned several times, as an advice: Get the parts before making any mods, so you can go back in case you are not ok with your change.

Click to expand...

Hi there, I’m about to begin with the modifications on my FX Impact X, I have already collected all the parts that I need to proceed, and have almost all the tooling ready to began with this project. Only question that I have (maybe a lot more will come for sure) is what sort of dremel bits are you using to perform the elongated brass port. I have several bits meant to be used for that purpose but so many different shapes and I’m not quite sure which one would work best. If you could share with us an picture of the recommended bits for grinding the brass port, it would be highly appreciated.

Gracias de antemano Eduardo

Click to expand...

The green Dremel bits work really well
 
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Just .22 for the ID.

This porting gives the most gain in .22 caliber. Larger bores also benefit, just not as much as .22

First seat a pellet before removing the barrel.

Flare the brass port to 7.4mm at it's entrance

Elongate the inside of the port getting close to the back of the seated pellet. The goal is to have a smooth radius that air can follow. Do not make the port wider or you can have feeding problems.

Blend the flared area into the elongated portion so that all surfaces have a smooth transition.

Enlarge the bottom hole in the pellet probe so that it's larger than the brass port. Knife edge the hole so that air crosses it smoothly.

Remove the top of the pellet probe above the feed hole. Don't square the back edge or it won't feed smoothly. Knife edge the parts you ground so that air crosses them without turbulence.

When done correctly the gun will feed any ammo the same as before modifications but you will get the same velocities with 20-30 bar less pressure in .22 caliber. The larger bores will gain performance but .22 gains the most.

When going above 145 bar a 4 gram hammer weight is necessary but the gun gives better performance and less ping with the hammer weight at any pressure.

Replace the C3 bumper with a Delrin washer.
 
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@ImpactHunter. Those images above, not the sizes, can be used to visualise the shape of the port your trying to achieve if you're porting a different caliber Impact than shown. The one thing that you don't want to do is widen the port down by the bore at all. The drawing's represent widening and elongating the outside and funnelling it down to the original drilled port and bore. You can enlongate the port a little bit, but the gains are negligible since the port has been funneled like that. The enlongated funnel shape created a Venturi and flows the air faster through the Venturi. 

Here's my latest port job for the .30 caliber. As you can see I did go into the back of the port a little, but I shaped it a little at a time while testing it with a slug and pellet. If you get it wrong the pellet or slug will go nose first through the port hole and clip or jam. Slow and steady wins the race. Trust your work and test as you go.

1572132500_1727758075db4d6942a5a00.90802155_IMG_20191026_192035814~2.jpg
1572132500_11119534585db4d69496e7a3.38720917_IMG_20191026_191937372~2.jpg
1572132501_3474531005db4d6951bf295.28913971_IMG_20191026_191611474~2.jpg

 
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Thank you heavy-impact and Airgun-hobbyist for your response

I read all the posts from the first to the last page,and since english is not my first language,there are a few

things (words) that I dont understand.and even Google can not translate to me.

I have Impact mk1 in 25 cal.I shoot only pellest for now.

I want to tune it but before I start doing it I want to know every detail of it how to do it on the right way. Thanks to you all, I have a place where to learn

I have replaced C3 bumper to Delrin,

I bought two spare pellet probes,45 cc external plenum and 6.35 valve seat.

heavy-impact

Hamer weight I did not plan to use since I will not go above 130 bar reg pressure.But thanks for advice I will put some 4 gram

One thing that worries me is BRASS transfer port and how to open (elongate) it properly.

If I understand you well it is important that inside hole in the brass port where pellet slides to barrel must stay the same to avoid jam issue?

Airgun-hobbyist 

The picture I found on the internet, if it is yours you did a excellent job




 
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