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Tuning Impact M3 compact .25 tuning question

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Jsbhunter

Jsbhunter

Member
Sep 25, 2021
7
0
Ohio, United States
Hello, so I've recently purchased an impact m3 compact that I would like to set up to shoot 33.95 gr pellets. I've been searching relentlessly to find someone that has posted their tunes for this set up but I've not been able to find what I'm looking for. So do any of you that have this same gun have the tune set up that will get me close? I'm pretty sure that I'll have to make some significant changes from the factory tune to shoot this weight pellet in the recommended speed range. Thanks. 
 
@jsbhunter, what have you done to your impact? any extras or just stock? i know there is a thread on tunes but if you haven't found it there you may need to do some testing. 
What are your current settings and what have you heard is the preferred speed for the jsb's? 

you checked here https://www.airgunnation.com/topic/your-m3-tunes-here/?referrer=1
 
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My gun is completely stock, I've have not adjusted anything as of yet and won't be adjusting anything for the time being. Currently chasing deer with my bow, but after that has ran its course I'm going to jump into getting this gun set up to shoot the 33.95gr pellets. 



The factory tune on the gun is : 1st reg 150 2nd reg 110 macro wheel 16 and micro 3.5. The gun was tested at my dealer shooting jsb pellets weighing in at around 16gr. If my memory serves me right the paper shows an average of around 900fps and a SD of just under 3. I will have to take a look at the paper to be sure.



I understand that every gun can have differences in tuning. From my research you can actually have a wide range of differences between tunes depending on whether you want to run high 2nd reg pressure to control how quickly the value closes, basically eliminating the valve adjuster all together. I'm actually leaning towards this type of tune vs running low 2nd reg pressure and hammer spring just below the max velocity. Then using valve adjuster to bring you fps within desired range. Again, just trying to use all my resources, I figure someone has already figured this out through significant testing and can save me some time. If not, I'll share my tune when I get it figured out. Thanks. 
 
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With short barrel, id be looking to dial in around 135bar + or - maybe 140

You want to get a lot of pressure behind that 33gr to get it moving quickly. Especially in a short barrel. But also don't want a lot of valve dwell. I'd start there, and see what your peak output is across the range of hammer adjustment. (make sure to dial out valve adjuster so it isn't stopping your valve travel short) Adjust maybe 10-15fps lower (backing off hammer) below its max output, and see where that puts you. Then you can tweak reg pressure further if need be and valve adjuster to reign in dwell or output if need be. Then check the hammer again to verify you're under its peak output. Or maybe you need to adjust closer to peak if you're falling to far off (this will happen if you increase reg pressure, opposite will be true if you decrease) 

Some guys do several shots to verify one adjustment. I only do one or two. I don't see the need to spend more time or ammo. It's pretty apparent to me whether a tune is proper or not. Or what's it's doing while I'm adjusting.

A good tune will have plenty of power output but will be noticeably quieter than a very similar (power-wise) tune that is otherwise inefficient 
 
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