Tuning Tunining Fx Dreamline to the Knee

[fiestaman]

Hi,I added upgrades to my Dreamiline .22 500mm superior liner, 2nd plenum, Huma TP and probe. No success with slugs. Very bad groups. 

I'm now tuning for JSB 18gr again. Before I changed stuff it shot jsb at 865 most accurate, that was factory settings and power 5 on the HW. Groups at 5.5 and max were a lot poorer. 

I've applied Bob O tuning process and started at 100bar reg and maxed the hammer screw. Max speed was 905fps. I backed off the screw 1/4 turn each time and fired a shot, then repeated for 43 1/4 turns until I seen a drop off in fps. On my graph it looked to me that at 34 turns was my knee so I backed the screw 9 1/4 turns and fell at 888fps which is about 2% drop from my max. I don't an 11 shot string there and got good Spread and SD. So I then shot groups. At 888 my group was poor. It was only when I turned down the hammer wheel to different settings which was setting A I got my tightest groups which was 860-865fps. 

My question is should I now drop back my regulator and start from scratch maxing my hammer spring until I'm 2% above 865fps = 882fps and then back off to try find the knee again and it should fall at my desired speed of 865fps where I get my tightest groups. 

I could leave it on setting A and reg as is but am I in the optimum efficiency range as I'm 5% below my max speed of 905fps. I don't have a nice Spread and SD at this setting 

Should i be trying to get the knee to fall where my best groups are at 865fps?images of graph and shot string below

 

[Solo1]

I don’t have a dreamline but do have 2 Mavericks. It seems to me that most guys tuning the new fx’s are starting too high on pressure. Try this. Crank your hammer spring to max then start at 70 bar and move up 2.5 bar till velocity drops. Then make minor adjustments down till you find your sweet spot. See if this helps. Good luck!

 

[Ghostranger169]

+1

 

[fiestaman]

I don’t have a dreamline but do have 2 Mavericks. It seems to me that most guys tuning the new fx’s are starting too high on pressure. Try this. Crank your hammer spring to max then start at 70 bar and move up 2.5 bar till velocity drops. Then make minor adjustments down till you find your sweet spot. See if this helps. Good luck!

Sorry, I don't really understand that, do you mean from where my settings are now, just put hammer wheel to max and up reg then from 70bar

 

[FelixS]

Hi,I added upgrades to my Dreamiline .22 500mm superior liner, 2nd plenum, Huma TP and probe. No success with slugs. Very bad groups. 

I'm now tuning for JSB 18gr again. Before I changed stuff it shot jsb at 865 most accurate, that was factory settings and power 5 on the HW. Groups at 5.5 and max were a lot poorer. 

I've applied Bob O tuning process and started at 100bar reg and maxed the hammer screw. Max speed was 905fps. I backed off the screw 1/4 turn each time and fired a shot, then repeated for 43 1/4 turns until I seen a drop off in fps. On my graph it looked to me that at 34 turns was my knee so I backed the screw 9 1/4 turns and fell at 888fps which is about 2% drop from my max. I don't an 11 shot string there and got good Spread and SD. So I then shot groups. At 888 my group was poor. It was only when I turned down the hammer wheel to different settings which was setting A I got my tightest groups which was 860-865fps. 

My question is should I now drop back my regulator and start from scratch maxing my hammer spring until I'm 2% above 865fps = 882fps and then back off to try find the knee again and it should fall at my desired speed of 865fps where I get my tightest groups. 

I could leave it on setting A and reg as is but am I in the optimum efficiency range as I'm 5% below my max speed of 905fps. I don't have a nice Spread and SD at this setting 

Should i be trying to get the knee to fall where my best groups are at 865fps?images of graph and shot string below

Now that you know your target fps, yes.

 

[Solo1]

I don’t have a dreamline but do have 2 Mavericks. It seems to me that most guys tuning the new fx’s are starting too high on pressure. Try this. Crank your hammer spring to max then start at 70 bar and move up 2.5 bar till velocity drops. Then make minor adjustments down till you find your sweet spot. See if this helps. Good luck!

Sorry, I don't really understand that, do you mean from where my settings are now, just put hammer wheel to max and up reg then from 70bar

What im saying is go back to square 1 turn your air pressure to 70 bar and max your hammer out then gradually turn up your air 21/2 bar at a time till your velocity drops then go back to highest velocity. This way you now know your peak air pressure for this hammer weight. To get more velocity you will need more hammer or just be wasting air. From those settings you can back down to find the velocity you have in mine or the sweetspot that the gun likes. You should also try to get your sd as close to 1 as possible

 

[mwils111]

I think you’ve already received some good advice but I’ll pitch in anyways.

First, your tuning process looks very good to me. Having the graph to understand how a given reg pressure reacts to hammer spring changes is key. 

Personally, I would probably leave the tune as is. Efficiency is usually better with a slightly higher reg pressure, as it means the gun will use small “sips” of high pressure air as opposed to long “huffs” of low pressure air. A slightly higher pressure will also work better with barrels that are on the shorter side, be quieter, and have the potential for better accuracy as there is less air behind the pellet to cause turbulence when the pellet exits the muzzle. I believe Matt Dubber has a video or two out there discussing his preference for higher reg pressure in shorter barrel configurations. 

The big potential downside of a slightly higher reg pressure is a less than ideal shot string, as velocities can rise as the fill pressure drops below the reg set point. I would try doing a shot string from say 50 bar above your set point down to say 20 bar below and see what the graph looks like.

 

[Solo1]

So how did you make out?

 

[fiestaman]

I went back and set the hammer screw to max. And started reg at 80bar. Increased until I got 880-885fps. Then shot and adjusted hammer screw off until I got to the drop off in fps which was 865-870. I shot some groups there and they were good but I also shot groups on hammer wheel setting 5.5, 4, 3. On setting 5 I got my best groups shooting jsb 18gr at about 840fps. Pellet on pellet. Also on setting 5 for Hades pellet on pellet. Amazing what 10fps does to groups. I should now be in the most efficient place for the gun. Reg is at 95bar and I think 17mm hammer spring gap. 

Problem is now I've just received Nielsen 17.5gr slugs in the post so I might have to go playing again

 

[Solo1]

I went back and set the hammer screw to max. And started reg at 80bar. Increased until I got 880-885fps. Then shot and adjusted hammer screw off until I got to the drop off in fps which was 865-870. I shot some groups there and they were good but I also shot groups on hammer wheel setting 5.5, 4, 3. On setting 5 I got my best groups shooting jsb 18gr at about 840fps. Pellet on pellet. Also on setting 5 for Hades pellet on pellet. Amazing what 10fps does to groups. I should now be in the most efficient place for the gun. Reg is at 95bar and I think 17mm hammer spring gap. 

Problem is now I've just received Nielsen 17.5gr slugs in the post so I might have to go playing again

Good glad you are on the road to fine tuning your gun! Have fun with the new slugs!!