FX FX Impact M3 - I Can't Tune It to Higher Velocities - Strange ???

Wolfy Smith said:

It's a 700mm Superior slug liner.

I'd have thought that most / all FX M3s were the same / similar out of the box. Unless there are lower power ones sold in the UK where I am ? But mine's on a Firearms Certificate, so I assume it's the same as all the other .25 cal M3s out there ?

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Just reading the license part… you’re in the UK? Wouldn’t be the first that comes with sub12 mods even though you get it on your ticket. If you’re hammer is maxed and you don’t get to 880 with 130b or more, chances are are you got a sub12 version or some parts/modifications thereof.

greenbeans said:

Just reading the license part… you’re in the UK? Wouldn’t be the first that comes with sub12 mods even though you get it on your ticket. If you’re hammer is maxed and you don’t get to 880 with 130b or more, chances are are you got a sub12 version or some parts/modifications thereof.

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There it is. I bet hes got a sub12.

One last think to make sure we’re not missing the obvious here: you did increase the hammer when increasing the pressure, right? Not the macro wheel, the micro adjuster. If not this is the very first thing for you to do. Micro to 5. 170b is probably way to much at this point but you’ll see substantially higher fps than what you get right now.

You have a lot of advice. You def don’t need a heavier hammer. I suspect something else is amiss. Transfer port blockage or some other blockage. I had a 600mm m3 .25 and at 120 bar it easily shot over 900 fps. Want to say like 915-920 or something. Can’t absolutely remember as it’s been awhile but I want to say the micro was at like 3.5 or at least ballpark.

When push comes to shove be sure to check the C1 adjustment.

rc4fun said:

When push comes to shove be sure to check the C1 adjustment.

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Some of us learn better by watching and reading, rather than just reading. So these are probably the 2 better tuning videos you'll find. You can achieve those numbers very easily with the 600mm and even the compact although that would require a lot of reg, hammer, and valve

Wolfy Smith said:

it's definitely not a sub-12

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You never know with FX, my .177 Maverick was a SUB 12 just dumped on the Danish FAC market,
It shot 13.43 gr MRD pellets ( factory 90 BAR on regulator and #7 / MAX ) hammer spring setting, at 575 FPS which i think if you do the math add up nicely to SUB 12
Mind you none of the regulators was capped.
Cranking the hammer spring fine adjuster in the hole in the hammer wheel got things going alright, and in 600 mm standard form it was in the end able to shoot everything up to 16 grain beasts at speed, on the negative side NONE of it flew well at those speeds,,,,, aside for the beasts which was like lasers.

My Maverick only really started to work after i put a 700 mm barrel in it, and started to experiment with heavier hammer and pin probe.

I should have sendt that Maverick back on day #1, but i am a stubborn old SOB that think he can fix everything.

Wolfy Smith said:

A big thank you to everybody above who has helped me so far - it's pouring down here so I may not be able to do much today, but tomorrow I'm going to:

- Reinstall the normal barrel, to try and eliminate the new slug liner as the problem
- Start back at around 100bar 2nd Reg pressure / 16 Macro / 3.5 micro thumbwheel / VA at '6' lines and start again.
- Go up initially in 10 bar increments, chrono 5-10 shots of the 34gr King Heavy MkIIs, then try adding a few clicks on the micro thumbwheel to assess the effect

I'll post what happened in a day or so.

Many thanks again - it's much appreciated !
Cheers
Sean

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Sounds like a plan! As mentioned wouldn’t have micro at 3.5 to start with though since you can’t be sure that this setting opens the valve completely at your pressure. It likely will but you cannot be sure. Just max out your hammer and valve to find your plateau for a given reg pressure. Then dial hammer back down to the knee and take the last 5-10 fps away with the valve adjuster. With a 700mm 120-130bar should get you to 920-940 with 34gr but obviously a good idea to start at 100 and work your way up.

What pressure gives you the plateau at around 930-940? You can obviously reach the same speed with a lot of different pressure/hammer/valve combos, but most of them will be a poop tune. You may currently be overdriving your valve and have hammer bounce, which would close the valve too fast and is not what you want for various other reasons as well.

I’m going to say it one last time: If you don’t know the pressure you need for 103-104% of your desired speed (“the” pressure, not a range), your tune will very likely not be right. To figure it out, open valve AND hammer to maximum. By that I mean the micro wheel. The macro wheel doesn’t to anything other than moving the micro wheel in larger increments, so put the macro on 14,15 or 16 and LEAVE it there during the ENTIRE process. Micro on 5. Then adjust the reg until you hit 940ish. Once you hit 940ish you KNOW the pressure that gives you what you need. No other pressure will do. More pressure will not do anything good for you because your hammer will not be able to do more or you’ll be too fast, less will not give you the target speed at the knee. Now dial back the MICRO 5 clicks tops at a time until you reach 910-915fps. Now start turning the valve, half or quarter times at a time until you are stable at 905 or whatever you’re trying to achieve. The valve is sensitive, so don’t overdo it. As always, 5-10 shots between adjustments. Note that we didn’t touch the Macro wheel at any time during this process.

If your valve still needs to be fully open for your speed, your C3 might be loose/too far out.

Wolfy Smith said:

Hello again Guys,

Kinda getting there now - solved one problem - the low muzzle velocity - but I now have another odd thing going on.

I basically solved the initial low MV by, as you all suggested, playing with the micro and macro adjustments.

So now I can easily reach 900+ fps with a wide range of parameters:

Reg 2 - 100 to 120bar
Macro at 8 to 16
Micro around 3.5

The gun will happily fire at 900+ fps - so I thought I just needed to optimise the tune. It was looking good - only a few fps spread, 2nd Reg pressure not too high...

But I can only get 900+ fps with the Valve adjuster at 6+ lines (backed all the way out). If I turn the VA to 4 lines, to try to finely tune the last few fps off for air efficiency etc - as almost all tuning guides suggest - then my muzzle velocity falls way off - back down to 750fps.

This happens whether the 2nd Reg pressure is at 100 or 120 bar - even if I keep Macro at 16 and push the Micro thumbwheel up to 5 - the MV still falls right away. I assume the VA is shutting the valve before it's fully discharged all its pressure behind the pelklet - but I thought the VA wasn't usually this far open ?

Am I doing anything wrong ? Do I need to increase 2nd Reg pressure still further ? Any ideas would be very welcome.

Thanks and best regards
Sean

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Some impacts have 6 lines on the VA rather than 4. I don't know the exact reasoning behind it or when the change occurred. Most of the advice that you've been given is assuming that your VA only had 4 lines. The VA is quite sensitive and the change between 6 and 4 would be significant.

I would leave it at 6 lines, get the velocity and SD close to where you want using the other adjustments and then gradually reduce the VA. The sound of the rifle will change a bit as it starts to run more efficiently. You'll need to test your tune on paper at 50+ yards to know if it's producing good results. Two tunes can achieve similar velocities, but one may perform better than another on paper.

You just need to fine tune it to where the velocity drops just a little bit. Forget the line number you are “supposed” to land on according to the internet and go with what gives results. You are just simply over shooting the sweet spot turning it in way too far.

Wolfy Smith said:

Thanks for all the input guys - I'm pretty much there now - alas I've run out of pellets over the weekend...

As Greenbeans alluded to, I was simply over-thinking things - especially with respect to the Micro and Macro adjustments. It turns out my VA will be over 4 lines at the sweet spot - but as Trucker 3573 says, it is where it is.

So I'll polish the tune tomorrow, after I've got a few more tins of MkII's - the process really seems to be a lot more straightforward than I thought, so once I've tested the accuracy on the range, I'll try out some slugs with the slug liner and see how they behave.

Many thanks again - it's really appreciated !
Best wishes Sean

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Good luck to you on a separate note: I sometimes wish I would have never started shooting slugs… that’s a separate rabbit hole and waaaay deeper than tuning for a pellet you’ll have to try many different slugs and speeds until you find one that’ll shoot consistently good…

greenbeans said:

Good luck to you on a separate note: I sometimes wish I would have never started shooting slugs… that’s a separate rabbit hole and waaaay deeper than tuning for a pellet you’ll have to try many different slugs and speeds until you find one that’ll shoot consistently good…

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That's why I only shoot slugs in similar weight of pellet I'm currently shooting. Its a lot easier.