FX impact tune - bottom up or top down?

[mschlee]

apologies if this is covered somewhere but I cant find it, seems there are at least 2 different methods for tuning the impacts and i'm wondering what most people use

1, what I'll call bottom up (start hammer and reg low and go up):
reg set low
hammer set low
valve open around 4
increase hammer till no increase in fps then stop, increase reg and start increasing hammer again till no increase in fps- continue till you hit target fps. then close the valve to the point it drops fps about 5 fps or so.

2, top down (hammer full on and then reduce)
reg set low
hammer set to max
valve wide open
increase reg pressure till your about 20 fps above target fps. then reduce hammer spring till fps drops by about 10 fps (you are at the knee). then close valve till fps drops another 10 and now you are right on target

I always use top down mainly because it seems easier adjusting 1 thing at a time but wondering if I should try bottom up?

I am also seen people fine tune fps with hammer and some with the valve - but maybe i'll start another thread on that.....

 

[greenbeans]

To me it depends on the tune you’re looking for. Bottom up makes sense if you are going for a lower power tune where you might end up on the wrong side of the plateau with the top down and you might see speed increasing with lower hammer. But I virtually always go top down since you’ll notice fairly quick if your on the wrong side of the plateau and can adjust accordingly.

 

[Trucker3573]

Always bottom up. Why slam the valve unnecessarily hard ? If you do a little research you can basically find out the reg pressure you will need for your tune. Well at least very close so little adjustment to that will be needed.

 

[6gun]

To me it depends on the tune you’re looking for. Bottom up makes sense if you are going for a lower power tune where you might end up on the wrong side of the plateau with the top down and you might see speed increasing with lower hammer. But I virtually always go top down since you’ll notice fairly quick if your on the wrong side of the plateau and can adjust accordingly.

This. Is it pellet life or low power, as much power as the rifle can achieve as delivered or max power moneybags tune? Each had a different reasoning but harmony and precision first or high power and reduce to to precision.

 

[greenbeans]

Always bottom up. Why slam the valve unnecessarily hard ? If you do a little research you can basically find out the reg pressure you will need for your tune. Well at least very close so little adjustment to that will be needed.

Fair point on the valve. I guess I rarely have reg low enough and don’t use tungsten hammer and the likes so never really concerned about smacking the valve too hard…

 

[mschlee]

interesting. so if I'm going for the most efficient tune I'll go bottom up, slinging high power for slugs etc top down,
i'm currently set up for 30 cal pellets and want quiet effiecient tune. I'll give bottom up a try ( btw I do normally start the reg a little bit below the recommended fx setting the hammer a little above when doing top down to try to avoid over slamming the reg but point taken)

 

[6gun]

If it makes you feel better ive been using the tungsten hammer with low spring energies for a few thousand rounds now. When I break a valve I will report back. The impact has rubber balls in the valve adjuster to act as a damper which I'm probably leaning on.

 

[greenbeans]

interesting. so if I'm going for the most efficient tune I'll go bottom up, slinging high power for slugs etc top down,
i'm currently set up for 30 cal pellets and want quiet effiecient tune. I'll give bottom up a try ( btw I do normally start the reg a little bit below the recommended fx setting the hammer a little above when doing top down to try to avoid over slamming the reg but point taken)

A high power tune can still be efficient it’s more about whether you push the gun or not. For example, my M4 with stock hammer gets valve locked at around 135-140bar. Stock hammer simply can’t do more. I have it set at 130 and it shoots 34gr pellets at 900, 30-34gr slugs between 950 and 910 with the same hammer/valve setting. So whenever I tune it for something else, all go top down if I know reg will be above 120ish. If I would want to tune for lighter/slower, I’d probably think about bottom up.

 

[Vetmx]

Bottom up. All the time no matter what projectile. Probably partially because it’s how we were taught when regs became the norm. And mostly because you can see how your gun evolves as you increase. Once all of that is in your notes, then your brain, it’s a lot of very valuable data down the road when you want to try something new. And knowing when your gun starts to run out of gas. Thus requiring a power do-dad.