Tuning How do I tune the FX Impact to be quieter?

I wonder if you could pad and may poke some holes in the shroud. 

The key is to run higher pressure and less valve dwell. Small high pressure burst that exerts its energy fast and early, and has mostly expanded by the time the projectile leaves = quiet 

Too many variables to honestly say. Gona have to mess with it and see how the gun repaonda to what inputs. I'd adjust pressure first to at least 125 bar and see if your power wheel won't still do 850fps without adjust the preset screw.

I have a pistol I tuned to be quiet and I left it at 135 bar. Compromise of volume and shot count. Higher pressure would have been quieter, but it gets over 100 shots as is and is sufficiently quiet. 

Pretty sure your reg pressure is way to low and your hammer spring to strong turn your reg pressure to like 150 bar and it could take up to 2000 pellets to brake your gun in 

I found with my 22 impact that it was much quieter with more regulator less hammer spring and then turn the valve adjuster until you notice the gun quiet down. I’d think the regulator should be in the 150 range. Maybe 145 but well above 100 

Mine is shooting 23gr nsa at over 1000 FPS with the reg set a 128 bars hammer max and valve open till the 4th line.. power plenum Ernest dual transfer port slug power kit and the superior 700mm barrel, after backing up the hammer spring a few turns and closing the valve till the 2nd line it’s shooting at 970 FPS very accurate and very quiet..

I know you live in canada put a donny fl on it and the sound will go away 

I know you live in canada put a donny fl on it and the sound will go away

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sure, we will invite you come and visit us, we can take you to a range and you just feel free to do that

There are couple of ways to quiet down the impact:



1. Raise the regulator to 120 bars and lower HS till you get 860FPS again and definitely will be quieter. 

2. raise the HS and reduce the valve to achieve 860 FPS again



The most effective way is actually use both but being 700 mm you can just leave the valve at 3 lines and usually it's good unless your reg is very low and 100 bars is a little low IMHO. If you want quiet and efficient you need higher regulator pressure. My impact .25 700mm is set at 125 bars but don't remember the preload. However at low I can get down to 700 FPS with the HADES and HS cranked up I can shoot 34 grain slugs over 900FPS. All I hear from my impact is the hammer noise and this is with just a small FX moderator. 



EDIT: Just realized you are in canada and no moderator, maybe try 140 bars and find 920-940FPS with one of the HS setting and then crank the valve down to 2 lines or till you get to 860 again. You want the valve to close well before the pellet leave the barrel! 

Going back to the advice from Long_Gun_Dallas earlier in the thread, that fundamental strategy is what works. 

1. Higher pressure
2. Short dwell

The idea is to smack the pellet on the rear end with a judicious pulse of high pressure air to get it started accelerating quickly, have the valve snap closed quickly while the pellet is perhaps only 1/4 to 1/3 of the way down the barrel, and allow this finely metered volume of air to continue to expand and accelerate it all the way to the muzzle. By the time the pellet makes it to the muzzle, the pressure will have decayed a substantial amount--the air having been allowed to expand into the final 2/3 to 3/4 of the barrel--and that's what determines the loudness of the report. A search on the term "residual pressure" or "residual pressure at the muzzle" may turn up some other useful threads.

Note, how well this "get it moving and then cut off the air supply" works is dependent on the porting. If you are trying to accelerate a pellet to a high velocity with a very short burst of air, that burst of air needs to be delivered to the back of the pellet in the most unrestricted fashion possible. For example, straining it through a restricted transfer port (a "power wheel" for example) defeats the purpose. You would need to keep the valve open longer to flow enough air to achieve the velocity you want, and that will make it loud.

Reducing the dwell time can be achieved a number of ways. With a design like the Impact, you have a valve limiter adjustment to manipulate it. Lacking such an adjustment, one may use a lightweight hammer. Either grind, drill, or turn material from it to reduce its weight, or make a new one from a lightweight material. A lot of people have replaced heavy steel hammers with plastic ones (MDS-impregnated nylon, PEEK, etc.). That approach is advisable only if the trigger design is a drop sear...a direct sear is apt to wear a groove in the hammer and create an unsafe condition. Yet another option is to use a valve with an assisted closing cycle (e.g. Cobra valve which uses a lossy pressurized chamber acting as an air spring, tuned by way of an orifice, that acts to snap the valve closed).

Just be aware that, like most things, it can be taken too far. Attempting to shave the dwell down to ever more fleeting levels will wreak havoc on consistency. That is to say the extreme spread may go through the roof, so think of it more as a balancing act than a singular goal.

nervoustrig ... Excellent play on the fundamentals.



Patrick