I'm sure you'll be happy with the results with a 22 barrel! It didn't take much to reach 1000fps with 30gr. Do you have molds for anything over 36gr in 22 cal? My goal there is 40-42gr.
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Fx Impact Fix & Mods for more FPS / FPE
- Thread starter AirSupply
- Start date
I know myself too well i just haaaad to try. Guess i got lucky and have adequate space between barrel and plenum, this is at 148bar reg.
Measure the thickness of the plenum wall.
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Nice to see that your plenum is fine. Can You pull out and put back the barrel when plenum and the whole gun is under pressure? Thanks.
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Where did you get the walnut parts ? They look awesome .
One more question , is the valve adapter threaded into the plenum? From the pics it looks as though it is a slide fit . This would put some real stress on the rest of the gun once filled.
One more question , is the valve adapter threaded into the plenum? From the pics it looks as though it is a slide fit . This would put some real stress on the rest of the gun once filled.
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I will try and measure when im home from work. Having some issues with my calipers but will try
Yes i can, its ever so slightly tighter than before but not by much. Gun is pressurized in the pics i showed. Showing clearance between plenum and barrel.
Thanks! I made the butt, cheekrest and forward grip, the pistol grip i bought from a guy in the states but he doesn't ship to Canada unfortunately.
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Thanks Guys . Love that walnut .
Now, if the ledge edge in the plenum is only preventing the housing from being pushed into the plenum too far . It will still push outwards when pressurized . This will for certain , put huge stress on the upper rail . To fix this , I would use retaining screws ( SHCS 10-32 shallow ) that go through both the plenum and housing . Similar to how the valve is retained in a Benjamin Discovery. https://www.ebay.com/itm/CUSTOM-VALVE-SCREW-KIT-for-BENJAMIN-DISCOVERY-safely-allows-up-to-3200-PSI/111868133852?pageci=c3c35406-0c76-4755-8128-c8718381743f&epid=1661966949
Now, if the ledge edge in the plenum is only preventing the housing from being pushed into the plenum too far . It will still push outwards when pressurized . This will for certain , put huge stress on the upper rail . To fix this , I would use retaining screws ( SHCS 10-32 shallow ) that go through both the plenum and housing . Similar to how the valve is retained in a Benjamin Discovery. https://www.ebay.com/itm/CUSTOM-VALVE-SCREW-KIT-for-BENJAMIN-DISCOVERY-safely-allows-up-to-3200-PSI/111868133852?pageci=c3c35406-0c76-4755-8128-c8718381743f&epid=1661966949
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Well then . Thanks Heavy for that info. What is causing the shift in barrel locations when pressurized ? Certainly the plenum can’t be swelling to the point of twisting the upper channel. Is there a radius cut into the ledge , maybe it is pushing the valve housing out of alignment .
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I think they all arent identical, some are basically touching when not charged with air. So once aired up its binding with barrel. I suggested in an email to not have it such a tight tolerance to the barrel on future ones. No one cares im sure if it's down another 1/8th or so.
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I believe there is run out from the part flexing while turning the OD. This causes the binding when pressurized. The walls are thinner than they should be for this diameter and pressure. There is also no radius on the inside corners. Even though the part is not properly engineered as a pressure vessel and tested to 2.5 times it's working pressure, I believe it is still safe for the way we will use it. It's not enduring large pressure cycles so I don't see metal fatigue being a problem.
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After reasemble all parts, I put barrel in place and then rotate plenum to get biggest gap and slowly tighten the screw to fix it... believe this is the best way.
Barrel slide without any problem with or wthout pressure so ... happy days.
Will see over night will hold the pressure.
Tomorrow will be done some testing with 70cc plenum and also + external 45cc ... let see what will be results.... 70 VS 115
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Plenum tested ... not sure what to say but looks like the same as I had with my 45cc external plenum. Maybe I gain 10fps more.
Good thing is that on 118bar, hamer at 17.3mm ( no hamer weight), valve on 2.8 lines ... jsb king heavy mk1 33.95gn at 935fps.
If on same presure max hamer and line 4 on valve ... I can get 965fps.
If I lift regulator on 150bar ... no to much speed increase ... 1050fps. I was expecting more but its almoust the same benefit I had from external plenum of 45cc.
So no diference if you use external plenum or this one. Just with this one you dont need to cut VH and no need to mod gauge hole.
Adding 45cc to 70cc ... no diference between 70 and 115cc up to 150bar. Speed with 70cc 1050fps adding 45cc speed was the same.
Good thing is that on 118bar, hamer at 17.3mm ( no hamer weight), valve on 2.8 lines ... jsb king heavy mk1 33.95gn at 935fps.
If on same presure max hamer and line 4 on valve ... I can get 965fps.
If I lift regulator on 150bar ... no to much speed increase ... 1050fps. I was expecting more but its almoust the same benefit I had from external plenum of 45cc.
So no diference if you use external plenum or this one. Just with this one you dont need to cut VH and no need to mod gauge hole.
Adding 45cc to 70cc ... no diference between 70 and 115cc up to 150bar. Speed with 70cc 1050fps adding 45cc speed was the same.
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So it would seem you have reached the point of diminishing returns . If you use the 1cc per FPE rule of thumb that makes perfect sense . I’m certain that with the added plenum what you are not considering is the gain in efficiency . It should do a bit better with the gain in regulated volume . I can’t wait to install my plenum . Michal contacted me this wee’ and it should be shippin* soon . I really didn’t want to go with the ER type plenum , one for looks and second I just didn’t like how it is secured to the block .
Thanks for the update .
Thanks for the update .
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When installing a hammerweight, do i leave out the plastic spring guide? I assume the rear part of fhe weight acts as the guide
*Edit seems like the right thing to do, i crescent mooned the probe and installed the HW. 900 with kh on minimum, can't do high power testing atm. And getting REAL comfortable with the guts of the Impact, was intimidating a bit at first coming from the super simple Royale/Boss but i got it now.
*Edit seems like the right thing to do, i crescent mooned the probe and installed the HW. 900 with kh on minimum, can't do high power testing atm. And getting REAL comfortable with the guts of the Impact, was intimidating a bit at first coming from the super simple Royale/Boss but i got it now.
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