FX Impact M3 Tuning Advice

[Jerkeejoe]

I know there are tons of tuning threads, but after doing a ton of searching and reading I’m still not sure I understand what’s going on with mine.

I bought it new as a .22 but installed a .30 barrel on it today. Reg pressure was 90 with the .22. I shot it at 90 just to see what it would do and it was around 550 fps with 44gr pellets.

I went ahead and increased reg pressure to 110, backed the micro off to 3, and opened the valve to around 4.5. Velocity was very low still, so I started dialing up the hammer. Ended up with hammer at max setting and was only getting around 860 fps. So I bumped the reg pressure up to around 120 and backed the hammer off again. Shot some more which resulted in pretty much the same situation.

Ended up at around 875 fps with max hammer pressure, valve wide open, and reg at 125. I can’t get it to shoot faster.

On the upside, the accuracy is fantastic, but I’d like a little more latitude with the tuning.

Is it possible I have the reg too high? Do I need a different hammer spring?

Any input is appreciated.

 

[25.cal]

Macro is at 16 correct?
Also, what is your barrel length?
How fast are you trying to go?

Put the hammer on 16, back your micro out until the gun doesn’t cock then give it some clicks back in until the sear catches and it stays cocked. That’s essentially your max speed at your given reg pressure.

If you want faster you need to up the reg. Try overshooting your speed by 3-5%. Then back down the hammer to get within 5-10FPS of target. Then slowly turn your valve in.

 

[dens228]

Barrel length matters greatly in this thread.
Right off the bat I'm thinking our second reg is too low. I'm shooting 35 grain pellets at 915 using a reg pressure of 108 in a 700 mm barrel. A shorter barrel would require me to increase the pressure, a heavier pellet would also require more pressure. Put your hammer spring at 3.5 and your pressure at 115 and go from there.

 

[Jerkeejoe]

Barrel length matters greatly in this thread.
Right off the bat I'm thinking our second reg is too low. I'm shooting 35 grain pellets at 915 using a reg pressure of 108 in a 700 mm barrel. A shorter barrel would require me to increase the pressure, a heavier pellet would also require more pressure. Put your hammer spring at 3.5 and your pressure at 115 and go from there.

It’s a 700mm barrel.

 

[dens228]

What speed are you looking for??
I still think your 2nd reg needs to be higher. I'd also close the valve a bit, maybe at line 4. That's the last thing I'd touch and only after, if needed, I got the FPS I was looking for with reg and hammer spring. I forgot you were shooting 44 grains. I'd bet you need at least 140 at the 2nd reg plus a hammer spring around 4+.

 

[Jerkeejoe]

Ok, cool. I'll try to bump the second reg up to bring the hammer spring down.

 

[MikeVV]

Why...do you need to go any faster with the pellet speed ? Hunting buffalo ?
875fps, should be enough for most any shooting, unless you are going for 200yrd distances.

Mike

 

[Jerkeejoe]

I'm more of a pterodactyl hunter actually. But I do some airgun elephant hunting as well.

Really though, I might not go any faster, but your question is akin to someone asking why their new Porsche won't go more than 100 mph and you asking why they feel the need to go any faster than that.

At the end of the day, I want to have a full understanding of how the gun functions and tunes. Researching and asking questions here is the best way I know of to learn that stuff. I also want to know if there is a problem with my gun as I've read a ton of anecdotal posts about others getting higher velocities with lower pressures and spring tensions.

 

[Trucker3573]

This is about right I think. I had a 700mm mk2 in .30 that at a 120 bar did a little closer to 900 but not much. Where I left it. I would first open the valve limiter up well past line 4. Bump the reg up to 125 bar and ease the hammer spring up as you shoot over an chrono and see how much of a velocity climb you can get. Go up small amounts so as not to go way past the sweet spot. Why you don’t want to crank the reg up a bunch at a time either. At some point you will hit a reg pressure that a stock m3 won’t open the valve effectively. Once you hit that top speed then slowly close the valve limiter until the velocity drops a little. That is usually a good spot. When you start all this just remember to have that valve limiter opened up as you don’t want that to be the limiting factor when you start tuning you want it being a limiting factor only at the end.