Tuning Impact tuning

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madeintheuk

madeintheuk

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Apr 19, 2020
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Washington depot, Connecticut, United States
So after some hard reading on various posts in this section, it seems the general consensus to tuning for most efficiency and quiet factor is higher reg pressures, and less valve dwell (am I using correct terms). Does this sound right? Also does this mean less hammer preload also?

I recently picked up an impact compact that has been built and tuned by the one and only Ernest Rowe, and I’m absolutely ecstatic with the gun, BUT (there’s always a ‘but,) it’s shooting crazy HOT right now (currently too loud for me to shoot in my backyard so no current chrony numbers) and I would like to tune it down for both velocity, and noise. It also currently has no shroud, and so my moderator doesn’t fit, so the loudness might not be a factor when I get those parts, but for my personal craving for knowledge, I would like to know from you experts what to adjust first. It’s currently on the lowest power setting also but the hammer weight is substantially larger along with having a slug probe, and dual transfer port. 


thanks in advance for any help.
 
"most efficiency and quiet factor is higher reg pressures, and less valve dwell" Yes this is so.

"Also does this mean less hammer preload also?" Higher reg pressures require more hammer not less.

If the gun is already on its lowest hammer setting and is still to much for you then you can turn the valve adjuster in a ways and if that is not enough you will need to lower the reg and readjust your hammer spring to a a lower power via the Allen set screw.

Remember to remove your tank and then purge the gun of any remaining air before you adjust the reg down to avoid damage.




 
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"most efficiency and quiet factor is higher reg pressures, and less valve dwell" Yes this is so.

"Also does this mean less hammer preload also?" Higher reg pressures require more hammer not less.

If the gun is already on its lowest hammer setting and is still to much for you then you can turn the valve adjuster in a ways and if that is not enough you will need to lower the reg and readjust your hammer spring to a a lower power via the Allen set screw.

Remember to remove your tank and then purge the gun of any remaining air before you adjust the reg down to avoid damage.



Click to expand...

Thankyou for the info. 
 
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With the Ernest gun you need to know is it has internal work and a heavy hammer weight more than normal so everyone's tune advice not work all the time but its always great to get ad much information as possible. As for it being loud a moderator will or should take that bark out you would be surprised how much. Before anything let's get you setup with a moderator or shroud or both and run some numbers. 
 
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Shroud and moderator (Sumo) mad a big difference on my compact 30 pushing 44gr pellets at 880, tried it without once and that was enough. Still quiet considering the energy. I sent ~ 50 down the tube tweaking the tune for the right sound and as noted the higher reg, heavy hammer were key.

Separately, re: backyard concerns, I've found early morning lawn service quite helpful. Not sure why, but it seems certain critters of interest head to my yard as soon as the mowers fire up. Zero turn mowers are great noise cover.
 
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I would imagine Ernest had that airgun flowing air really well. You could probably pull the two added slug kit spacer weights (Just two spacer rings added to the back of the hammer for more hammer weight) out to lower the hammer energy a little more allowing you to lower the reg pressure a little more, too. Then there's the light valve spring from the slug kit that could be changed back to a stock valve spring. It's just a little longer to take up the spacer weights removed. Basically removing the slug kit effect on the valve and hammer, but keeping the pin probe. These two items would help you to back the power down more while still keeping a decent reg pressure for short fast blast of air needed for quietness, especially for a compact barrel length.

I use a DonnyFL Shogun, swapping it between on my .25 and .30 cal. barrel setups This along with being tuned so that the valve closes before the pellet exits the muzzle allows mine to be "backyard friendly" at 90 FPE or less in .30 cal. Ironically, to me, more so than my beefed up .25 cal Marauder is using a pickle tuned to only 55 FPE. The report frequency is much lower on the FX thus less noticeable to the ears while shooting at a rubber mulch filled tote/bin.
 
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Ok guys, so I jumped the gun here when I made this post. I should have waited till it was moderated and I could shoot a string. 
Brawler1588 was nice enough to loan me his shroud and snipe to get this thing shooting in my back yard, and so I ran some strings over the chrony this evening. On low power im getting around 830 with 34 grain jsbs, and at high power it’s just shy of 900. It is an air hog right now, but me thinks the combination of heavy pellets and short barrel probably aren’t ideal for that. I’m going to try some hades in it tomorrow evening along with some 25 grain nsa slugs I have, and see what I get for speeds on those, then it’ll be accuracy testing. 
thanks for everyones help, I’ll be using what I learned here to tweak it in the future if need be, and I now have a better understanding of how these things work in harmony. 
thanks again!
 
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All good advice given above, Andy, and that was super cool of Matt to help you out with a shroud and moderator.

At those speeds, if you decide to keep it there or go lower, don’t disregard the factory, 3 piece tube that FX sends with their new guns, as a moderator. Those things actually work well for those speeds. If more hush is needed, combine two center sections of these tubes. That set up is what I actually favor and have one on my Impact, and one on my wildcat 30, both of which shoot hot enough to burn your hands if you pick them up, ha ha!

I had 3D tapered baffles custom made to stack inside these tubes from end to end. 7 total inside. I’ve heard of others doing the same with these tubes, except they source hair curlers from the local dollar store, that supposedly fit just inside the I.D. Oof the FX tubes. I’m gonna one day try the hair curlers to see how they compare to the baffles.

As far as a shroud, you should be able to buy one from FX for around $60 or so, and that’s just the shroud, no ends and the fitting inside that threads onto your liner lock. I just bought a set up for a 600mm barrel and it came out to just under a $100. DonnyFL also sells FX Impact barrel shrouds, all ready to go. Same length as factory.
 
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I saw Donny sold shrouds, but his 500mm was only 177/22. I didn’t know if it would work being mine is a .25, but I also didn’t know what is so different about them 🤷🏻‍♂️


this is all great advice. I haven’t shot any large shot strings yet, and I’d like to get my extreme spreads down a little as well as lowering the air use. I won’t really need to shoot heavy pellets out of this being s pesting gun, and I should probably save them till my wildcat is done anyway. Lol

you guys are great with all these response. Thanks again!!
 
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Been pretty nasty weather up here for chrony work, so haven’t had a chance to get out and chrony the lighter pellets yet. 
2 things are going through my mind at the moment, 1 being how crazy high the extreme spread is, and 2 is how much air it’s currently using. I know it’s only a 300cc bottle right now, and it takes more to get the pellet up to speed with a short barrel, but I wasn’t expecting only to get 20 or so shots before it drops below reg pressure of 150 bar. Also when it does this , the extreme spread tightens right up as it fall off the reg. So does this mean the reg pressure is too high for the speeds I’m getting? Or is there other causes im overlooking.

keep in mind this is the first time I’ve ever tinkered with an impact. The valve adjustment has never been there in any of my other guns, so tuning this is all brand new to me. 
thanks!
 
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So finally got some nice weather and a chance to do some more chrony numbers. This time with the hades. All I can say is WOW. who would have thought that pellet weight made such a HUGE difference in extreme spreads!

6ABEF4EE-9620-42A7-B785-71CBF22512FA.1623273749.jpeg



Yes, that’s 66 shots to get these extreme spreads and standard deviation, and with unsorted hades pellets!

Ernest obviously tuned this with these pellets in mind, and tuned it PERFECT for them. I haven’t tested accuracy too much, but for chrony purposes I was shooting into my wood pile burm at about 25 yards and stacking them. 
im over the moon pleased with this setup. Thanks all for the lessons in tuning. I’ll be leaving this alone for now unless accuracy out to further distances isn’t that good. It would be nice if the hades shot good at this speed just for the flatter trajectory. I’m also getting 38+ shots from a 300cc bottle. I didn’t go too far because I didn’t want to fall off the reg and ruin my shot string. 
another happy impact owner here!
 
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