Tuning FX Impact Mk2/M3 - slower first shot - no reg creep - quasi-scientific analysis

Some people are fixing this issue by increasing hammer weight by 3 to 4 grams. 

I wonder if it can help. May be a heavier throw over powers the sticking force greatly.

Bhaur

48 hours and velocity is good. Done.

Are folks that run peek poppets machining those or can those peek poppers be purchased aftermarket?

ever since I got into PCP’s I’ve heard of folks upgrading to peek poppets on all sorts of pcp platforms. If it is a superior material over delrin why hasn’t the manufactures of Airguns incorporated this peek into their valve systems? Curious

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Peek is a better material it is harder to get a seal with it is a harder material and you can make it smaller than the derlin needs to be making it smaller means more air flow easier opening it doesn't deflect like the derlin does either which also helps it open easier. I don't think anyone is selling them but people make them for them selves I have changed over a marauder to peek a hm1000x and a air force condor to peek the poppet's overall size can be smaller because of strength of it versus derlin with derlin you need more overlap on the valve so it doesn't get pushed into the throat with peek you only need about 1/2 of the over lap hope that makes sense to you basically peek is stronger and can make the poppet smaller with less flex just harder to get it to seal 

48 hours and velocity is good. Done.

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That's great how low was first shot just curious 

Maybe 4fps. Fired 5 shots and didn’t even record the velocities. They were all within where I need them to be. No more warming up the old farm tractor. Weather permitting, may try a 100yrd cold shot at a 1.5 inch spinner tomorrow. 

Cool. I won't have to switch the derlin poppet then I'm glad this mod worked out 

I keep how I tune for slugs pretty close to my chest but I can say my second reg is at 126b and the hammer spring is set at least 3% below the plateau. Then another reduction with VLA.

Chronied 5 different guns yesterday, just out of queriosity. All sitting in closet for days, or week. No dryfire, but pellet or slug from first shot.The first 3 guns was within 15-20 fps starting with "best", to the worst. Fx bobcat (less than 10 fps), taipan veteran, AGT vulcan. Then a FX maverick, and FX impact, which was roughly 50 fps slower on first shot. The impact needed 4-5 shots until stable, and the mavetick maybe 3. The 3 "best" gun has been tuned for a specific pellet. The impact is in a midle tuning prosses, for slugs, and might be far under the plateu. Same with the maverick which is new, and shot with a "random" setting on the wheel, and might for all I know also be way under the plateu. 

Not sure if it makes a difference, but my impact with a mk2 plenum, had a .177 barrel. A litle reg creep and sitting a long time, might need a few more shots, than had it been a .25+ cal. which would drain plenum faster? 

Today I fired a 100 yard cold shot. Reg crept 2b, if you even want to call it creep. I was playing with the 2nd reg yesterday trying to get it to settle where I wanted it. Gun sat for 24 hours. Didn’t feel like walking down there so I took a pic through my scope on 20x. Very pleased. This is what I expect for $2k, a $2k scope and all my efforts tuning. That’s a dead mouse at 100 yards first shot accuracy. But as an Impact owner, there is a good possibility my gun will poop the bed if I brag about it.

Maybe as someone talked about earlier, having both higher hammer spring force, and valve spring force turned in at the same time will ovecome some of the stiction on the first shot?

The difference about letting the air pressure being the main force holding the valve closed, with as lilte valve spring as possible, as having more valve spring force doing the work, is that air pressure start with the highest force when valve is closed, and friction is static, and drops when air runs buy. A spring start with it weakest force when valve is closed (static friction), and increase as the valve is open (dynamic friction). As I understand the M3 has some of the old rubberball system integrated in the valve adjuster, so maybe alloving the valve to bump on the ball, will allow it to have roughly the same travel on a cold shot? It is probably not an option if the gun is maxed out at 140+ bar, as the valve spring in that scenario probably need to have as lilte force as posible, and no bumping on the ball ever will happen.

Cranking up your hammer strike is not a fix, it’s a bandaid covering a problem. As I talked about before in this topic, when you don’t have your hammer strike set in a happy place, your gun can fall off a slug tune as you approach the regs set point. Pellets might not care but I’ve never fired a pellet out of an Impact at a target since 2016. Even all my pellet guns have my hammer strike set up so my shot string looks like a dead persons EKG from a full fill to refill at the regs set point. Until FX fixes this, the only way to remedy the problem is do what we did.

As mubhaur mentioned, you can add weight to your hammer. But you will immediately have to counter that by turning your VLA in more. And from a tuning standpoint, nobody wants any more hammer weight than what is necessary because it has a negative effect on harmonics.

As mubhaur mentioned, you can add weight to your hammer. But you will immediately have to counter that by turning your VLA in more. And from a tuning standpoint, nobody wants any more hammer weight than what is necessary because it has a negative effect on harmonics.

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I can understand that. I personally work in the 100-120 bar range on my gun, as I either shoot the .22 25 grain JSB knockouts, or now the 13 grain .177 knockouts in my newest 700mm barrel. For my setup, I have more options to work with, as my powerlevel is way lower than the OP's with both hammer spring force, and valve. I have a mk2 plenum, without the ball. I have personally not been to woried about the first shots, as I am no hunter, but I noticed the overall ES improved on my last .177 pellet tune, when I added a litle morre tension on the wheel, and a lilte more force on the valve spring. But that was when I was working with 80-90 bar. The gun just seemed a litle "sloppy" with less valve spring force, and no pretension on the hammer wheel. But totally different setups I know

@mubhaur, how is your testing going?

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Testing results of RAW are promising. 

Bhaur 

Hi guys,

It's a little silent here. I've just completed one more test:

- original valve poppet (Delrin),

- Viton80 2.84x2.62 PowerPlenum oring,

- PEEK backup washer,

- weak valve return spring (the one from Huma High Power Kit).

Vmax on a given reg setting (150 bars): 276m/s

V0 set to be ~254 m/s so way below plateau.

First shots after 72 hours of a valve inactivity time: 253m/s, 255m/s, 253m/s.

No stiction issue whatsoever.

I am going to prepare a summary of the issue soon. It will be available in the first post of this thread.

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Great. 

What do you think about which individual mod played the most of the part.

Is it Viton, Peek part or light valve spring?

In my experiments when I install the light valve spring, NBR O ring and increase the hammer weight a bit, the issue gets resolved 99%.

In fact I am not after achieving the very 1st shot to be perfect. My need is that if I take my gun out after many days even if the 1st shot is at a bit lower fps, the 2nd and onward shots should be perfect.

Further if I put away the gun for a few hours to 12 hours there should not be any increase in extreme spread including the 1st shot taken after 12 hours of the last shot.

Thus if I take out the gun after many days and make a dry fire I am good to go for all the day long for hunting as well as target practice whatsoever. 

So in my case, the very 1st shot doesn't haunt me.

Dear Seeker, please don't take me wrong, I have all the respect for your achievements and have leaned from whatever you have done. 

Bhaur