Prior to this, the FPS was 877-882@135 bar, but now it will do that at 115-120 bar. At 125-130 bar it is averaging a tight 890fps spread. I haven't ran the regulator up any further yet. The previous modifacations were increased hammer weight by about 6-7 grams with a 1.5mm spring preload, and enlarged the valve port to 6mm.
FX Impact valve housing modifacations
- Thread starter Airgun-hobbyist
- Start date
Prior to this, the FPS was 877-882@135 bar, but now it will do that at 115-120 bar. At 125-130 bar it is averaging a tight 890fps spread. I haven't ran the regulator up any further yet. The previous modifacations were increased hammer weight by about 6-7 grams with a 1.5mm spring preload, and enlarged the valve port to 6mm.
DON'T drill these holes in the valve housing. These were drilled and filed too thin. The straps are not strong enough being this thin at the holes, causing the failure. On the second attempt to gain air space I just filed the straps thinner until satisfied with strength and still gaining air volume.
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Just my pride. ;-) Truth be told, I don't mind that it failed in my experimenting. I'll be ordering another housing on Monday, and now we know the limitations of those extremely modified (drilled and thin) straps at 150+ bar. "Kid's, don't try this at home."
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Oh man, bummer! That was some really impressive work! Sorry to hear it failed but it sounds like you understand how it goes … great results come with at least some risk! Not everything is going to work out right the first time and you've got the right attitude for doing this kind of experimentation. I hope next time the results turn out better for you. I love to see people with the cojones to go at it like this without worrying about negative outcomes. I applaud you and look forward to hearing the numbers after your next trial and success! Here's a +1 to help with that damaged pride! lol
Stoti
Stoti
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Bummer, it will be nice to know the power increase of doing that mod only, I have been told that making mods on the VH does not give much power and is not worth the job, but personally I don't know. All I know is that I get arround 930fps @150 b 700mm barrel out of the 44gn without enlongating the brass port or pellet probe, with a 2mm preload hammer weight, 5.8mm VS. I do have spare VH for mods, but I haven't tried just yet.
Anyway, thanks for sharing that!
Anyway, thanks for sharing that!
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I was thinking about power last night after trying the .30 for the first time in the Impact guise not Crown. Velocity was 860 with the .44's but 840-850 with the 50's which I thought was strange although they seemed much tigher to load.
So edosan 930FPS with the 700mm .30 barrel, did you ever have a 600mm barrel? if so what did it give you VS the 700? I found in .25 you gain 40FPS with 700 over 600, is it similar with the .30?
Don't think I will be trying the mod the OP did!
So edosan 930FPS with the 700mm .30 barrel, did you ever have a 600mm barrel? if so what did it give you VS the 700? I found in .25 you gain 40FPS with 700 over 600, is it similar with the .30?
Don't think I will be trying the mod the OP did!
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That sounds about aright as far as loosing 10-20 FPS going up from 44.75 to 50.15 pellets. Don't be afraid to experiment. My Impact would only go to 840-850fps when I first started into the power tune. First thing I found was that the probe wasn't cycling the pellet all the way into the transfer port, so the front of the probe was blocking airflow. Adjusting that and enlongating the port only gained a few fps. The biggest gain in speed prior to the port job was from additional hammer spring preload and weight coupled with the enlarged valve seat I opened up to 6mm. That gained 30 fps. It seems as though the valve stem and hammer spring struggles to keep the valve open long enough for sufficient airflow to push a 50 grain pellet past the 850 mark. With the hammer weight holding the valve open, coupled with the 6mm valve seat, the port job was by far the biggest gain in speed. Removing metal from the valve housing is not done for a performance gain, but rather to gain more air space so there is sufficient air available to flow.
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@spray1mark only the 700mm barrel on 0.25 and 0.30, I do have the 600 barrel on 0.22, the speed gain it supposed to be around 5 to 10% from 600 to 700mm, I will order the 700mm 0.22 cal soon, then I will know for sure.
For more power and speed, and with all the experiences gathering so far, the best mods for the impact probably are: elongated ports, larger valve seat, hammer weight with spring preload and larger valvetube
For more power and speed, and with all the experiences gathering so far, the best mods for the impact probably are: elongated ports, larger valve seat, hammer weight with spring preload and larger valvetube
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It's running JSB 50.15 grain pellets down range at 970 FPS at 170 bar! All I need now is the extra plenum space for more air.
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With a cold gun this morning and a few pounds of regulator creep overnight, the first shot was a 980 FPS @ 174 bar. Now that I know maximum speed is on the maximum recommended amp regulator setting, it is time to start tuning for a balance of accuracy, speed, and to gain some air reserves with a lower regulator pressure.
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Interesting, for sure. I just installed the Huma regulator, with the 30cc plenum, in my Wildcat Mkll 30 cal. With my reg pressure at 160 bar, JSB 44.75 I'm getting:
Avg 890
Hi 905 Lo 879
Spread 26 STD Dev 8.8
7 shot group
I'm happy!
Avg 890
Hi 905 Lo 879
Spread 26 STD Dev 8.8
7 shot group
I'm happy!
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