Tuning Help with Impact M4 700mm Tune

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Dr. Fumbles said:
You sir are a saint. Thank you for trying to help me.

Due to something else I ended up not going into work today. So I have the day off and will try it again once more. I have about 600 Pellets left at this point. I ordered more yesterday but they’ll be here tomorrow or the day after.

I’ll read over this again and try once more today. I’ll also watch that other vid once more before trying.

Yup, degassing the gun if I’m going down more than a few bar at a time.

There was a video by Utah Airguns where they went over their tuning process. In that video, they explained that you start off with low reg pressure and dials set to the middle and work your way up one click at a time. Once the velocity drops, go back 1 click and bump the reg up and continue. I thought I was doing that. But no matter how many clicks I moved up after bumping the reg up, it would still drop unless I went down on that wheel. Very confusing.

I don’t believe I’m familiar with indexing the barrel. I’ll have to look that up.

Edit: I just watched some vids on barrel indexing. I can confirm that when I shot at 50 and then 75 and then 85, my shots were dropping straight down as I went further back. They didn’t go off to the side at all. I believe Utah Airguns already indexed it before shipping it out to me.
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If I were you I’d start at like 110bar on the reg and find the max velocity as described and work your way up from there. You should have no trouble getting passed 900fps. Open the valve to 4.5ish lines (wide open) and increase the wheel until you don’t see a speed increase, bump the reg up 5-10 bar and see if speed increases. If it doesn’t there may be something else going on. Follow up when you test. I’ll help diagnose whatever it is
 
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Floridaman2005 said:
If I were you I’d start at like 110bar on the reg and find the max velocity as described and work your way up from there. You should have no trouble getting passed 900fps. Open the valve to 4.5ish lines (wide open) and increase the wheel until you don’t see a speed increase, bump the reg up 5-10 bar and see if speed increases. If it doesn’t there may be something else going on. Follow up when you test. I’ll help diagnose whatever it is
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Ok, followed the entire process again from the beginning. I’m currently at 120 bar on reg, macro 16 and micro 4.25-ish. Valve adjuster is at about 4.5 but I haven’t started messing with that yet. I’m currently at about 920-ish fps. Do you think I should still try to aim for higher speeds? I’m not really sure what velocity I should be aiming for with these pellets.
 
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Dr. Fumbles said:
Ok, followed the entire process again from the beginning. I’m currently at 120 bar on reg, macro 16 and micro 4.25-ish. Valve adjuster is at about 4.5 but I haven’t started messing with that yet. I’m currently at about 920-ish fps. Do you think I should still try to aim for higher speeds? I’m not really sure what velocity I should be aiming for with these pellets.
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You want to be between 880 and 920ish. This where you have to kinda start latter testing. Once you find a brand/ grain, your gun likes to hone in the accuracy even more.
 
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Dr. Fumbles said:
Ok, thank you. Then I’ll try seeing if I can get the accuracy to dial in from here. Appreciate the help!
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Yeah, I’d say you’re at a good speed, though you could play with going up or down depending on accuracy. Shoot a group or 2 and then you can use the valve to clip some speed off the top. This should really tighten up your groups, help be more efficient on air, and let you hone in on the right velocity. Now that you are at 920 you can come in on the valve and should have much better spreads and deviation and you can use the valve as a fine tune knob like it’s intended to be. Sounds like you are on the right track. Speed is a matter of preference and performance. But at 120 you have room to increase if you wanted to try it. But it sounds like you tuned it correctly from the top down and you should have much better results from tuning this way 👌
 
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Alright, reporting in. Spent the day again shooting. I feel like I was able to make actual progress today. I followed the steps described here, in the vids, and also called up Utah Airguns and they helped walk me through some stuff as I did it.

I got my reg at about 125. I saw the best groups at the 900-ish fps range. I was able to use the micro wheel and then the valve adjuster to get the groups down to about a nickel or slightly smaller at 50 yards. Honestly for ground squirrels that would have been fine. But then I moved the target back to 75 yards and the groups were the size of the palm of my hand or slightly smaller. So that was not fun. Was almost ready to throw the rifle into an active volcano right then and there.

I ended up shooting through all my JSB pellets. But I had a full tin of AEA’s so I figured what the hell, can’t hurt to try those and see. BOOM all of a sudden I’m getting nickel sized or smaller groups at 75 yards with the AEA’s! Every once in a while a group would open up to about an inch or slightly more (no wind today so I don’t know why) but for the most part I was seeing good performance from the AEA’s. I think my gun maybe just doesn‘t like JSB’s.

I also noticed that with JSB’s I had an ES of 17.6 (with 25 shots) but with the AEA‘s I had an ES of 9.2 and SD of 2.something. So I’m gonna order a bunch of AEA’s and try to tune for those next week after this upcoming rain passes.

900 fps seems to be good, but I’m reading that a few people have seen good performance at 960 with the 33.9 grains. I’ll take pics of all my current settings and maybe try to see what AEA’s do at 960 if I can get there. It seems that I will need to work the reg up to about 140 for that. I’ll report in again after I get a chance to do so.

I wanna thank everyone here that’s replying and offering advice to help me. If any of you happen to come to the Sacramento, California area I will buy you In-N-Out Burger or something else for lunch as a thank you! This is a great forum.
 
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Dr. Fumbles said:
Alright, reporting in. Spent the day again shooting. I feel like I was able to make actual progress today. I followed the steps described here, in the vids, and also called up Utah Airguns and they helped walk me through some stuff as I did it.

I got my reg at about 125. I saw the best groups at the 900-ish fps range. I was able to use the micro wheel and then the valve adjuster to get the groups down to about a nickel or slightly smaller at 50 yards. Honestly for ground squirrels that would have been fine. But then I moved the target back to 75 yards and the groups were the size of the palm of my hand or slightly smaller. So that was not fun. Was almost ready to throw the rifle into an active volcano right then and there.

I ended up shooting through all my JSB pellets. But I had a full tin of AEA’s so I figured what the hell, can’t hurt to try those and see. BOOM all of a sudden I’m getting nickel sized or smaller groups at 75 yards with the AEA’s! Every once in a while a group would open up to about an inch or slightly more (no wind today so I don’t know why) but for the most part I was seeing good performance from the AEA’s. I think my gun maybe just doesn‘t like JSB’s.

I also noticed that with JSB’s I had an ES of 17.6 (with 25 shots) but with the AEA‘s I had an ES of 9.2 and SD of 2.something. So I’m gonna order a bunch of AEA’s and try to tune for those next week after this upcoming rain passes.

900 fps seems to be good, but I’m reading that a few people have seen good performance at 960 with the 33.9 grains. I’ll take pics of all my current settings and maybe try to see what AEA’s do at 960 if I can get there. It seems that I will need to work the reg up to about 140 for that. I’ll report in again after I get a chance to do so.

I wanna thank everyone here that’s replying and offering advice to help me. If any of you happen to come to the Sacramento, California area I will buy you In-N-Out Burger or something else for lunch as a thank you! This is a great forum.
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Awesome 👏 I’m glad you were able to make it click and made some progress with it! Sounds like you are on the right path! I would encourage you to try more ammo as well. Grab some small tins of a handful of different types and do the same process for each one and find what works in your gun. Each gun is slightly different.

Either way glad you kept at it and got some results! Now that you got to this point, you should have no trouble repeating the process 👍 have fun!
 
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