FX Anyone have a tune for .22 JSB MRD in a Panthera with 500mm barrel?

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NAProf

NAProf

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Oct 10, 2021
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Lewes, Delaware, United States
I have been trying to find an tune for .22 JSB MRD pellets in a 500mm Panthera. The barrel is a 1:24 twist standard Superior STX liner and I have the 4mm head 12 g hammer weight. So far I can get pretty good 50yd groups when I get the pellets to fly around 900fps. My problem is that all the tunes I have tried in this speed range either blow lots of excess air (2 magazines per bottle fill), have ES of 40 and SD of 15, or both. When the velocities are much off of 900 the pellets wander all over the place. I tried 880 FPS and got rid of the air consumption issues, but not the inconsistent velocities. The regulator is holding rock steady and I have polished the barrel, the spring ends, the hammer, etc.

Any ideas on what to try? Or should I go back to the 18.1 gr pellets where I can get a good (and accurate) tune at around 880fps? (Want to shoot well in local 100 yd competitions and really don't want to buy a 600mm barrel).
Cheers,
Greg
 
If you don’t like the air consumption at 900fps then you will really hate it if you install the correct liner and get them going 950fps. So you are going to have to face some facts. Either be happy with one mag or understand that your gun isn’t meant to shoot something that heavy. You bought a 18-20gr pellet gun. If you try to make it something it’s not, neither of you will be as happy as you could be.

I had to edit my reply. I was thinking you had a compact Panthera. Either way, you are still going to have to lean on the gun pretty hard to get those MRD’s up to speed. Does the Panthera have a slug and pellet port on the barrel? If it does, make sure you are using the slug port.
 
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To LDP and Vetmx,
Thank you for taking the time to respond. I appreciate your insights. I think I am probably asking too much to get the MRD's to shoot at 900 fps from a 500mm barrel. The Maverick I use to have shot them really well, but it was a 700mm barrel. I might try really slowing them down to something like 800 fps to see if I can shoot them accurately at 50 yds. The problem I had with the Maverick was that the pellets were great out to 75 or so yards but started to spiral after that. Possibly shooting them at 800 fps might help with that.
Cheers,
Greg
 
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Vetmx said:
I’ve shot MRD’s out of my M3. You are going the wrong direction speed wise and you aren’t using the right liner. Once you have the right liner and speed, there will be no spiraling. But you are going to need to be north of 940fps.
Click to expand...
I don't shoot the MRD, nor do I have a HP rifle, but from all I've heard and read, this sounds right. I don't know if it's available, but a faster twist might allow better accuracy at the lower velocity.
 
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My tune with the supplied liner in a 500 dynamic mrd at 960

IMG_3166.jpeg
 
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I "spent" several dozen tins of MRD's from 3 liners, and I can confirm these are not pellets and not slugs neither, but some thingy in between.
50 M great grouping, 75 M acceptable groups, 100 M no bueno no matter what I did. I got that feel in my beer belly that these MRD's not designed for 100 M.
FX Impact MK2 and Edgun with x600 and x700 liner conversions, tried TWR's 1:15, 1:24 and 1:27 .
Resizing these pallets helped some, but switching back to 18gn is much less pain.
Maybe thomasair can chime in what TR he can shoot these much better.
 
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Vetmx said:
It’s quite the opposite. He needs a faster twist rate and even more speed with that pellet.
Click to expand...
Well, a faster twist is what I mentioned. When I was developing BR loads in CF competition, I found that a faster twist would stabilize a long bullet, or, a higher velocity with the slower twist. Maybe that experience doesn't translate, but it seems plausible.
 
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Thank you all for your input!

I tried the tune ViperJoe suggested, and it is much better than where I had been. Even at 150 bar for regulator pressure I was able to shoot 3 magazines before dropping off the regulator. The MRD's were running at an average of 956fps and at 50 yds the accuracy was "much better". I will play with the tune a bit to see if slowing or speeding up 10-20 fps helps accuracy.

Note to elh0102 - I have been doing a little research on twist rates. Pellets are way different than bullets on this. There are well define twist rates to get bullets to "go to sleep" (reach dynamic stability) depending on length, mass, velocity, and caliber (See Bryan Litz's book on applied ballistics about gyroscopic stability factor "sg"). No such thing for pellets. Go back and look at some of Matt Dubber's "Ballistics 101" videos where he talked about the development of the FX STX liners. It seems for pellets you need spin as it leaves the barrel to keep the disturbed air behind it from causing it to get too much out of alignment and bleed a lot of velocity in having the skirt correct alignment by drag. After that, you need very little spin for pellet stability. In fact, too much spin causes spiraling. So, he talked about finding that fine line between enough twist for initial stability but not so much as to induce spiraling. I think this is why the FX Superior STX liners for .177 have a 1:18 twist rate and the same liners for .22 have a 1:24 twist rate. The smaller lighter .177 pellet needs more initial help in stabilizing out of the barrel. Thoughts?

Cheers,
Greg
 
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NAProf said:
Thank you all for your input!

I tried the tune ViperJoe suggested, and it is much better than where I had been. Even at 150 bar for regulator pressure I was able to shoot 3 magazines before dropping off the regulator. The MRD's were running at an average of 956fps and at 50 yds the accuracy was "much better". I will play with the tune a bit to see if slowing or speeding up 10-20 fps helps accuracy.

Note to elh0102 - I have been doing a little research on twist rates. Pellets are way different than bullets on this. There are well define twist rates to get bullets to "go to sleep" (reach dynamic stability) depending on length, mass, velocity, and caliber (See Bryan Litz's book on applied ballistics about gyroscopic stability factor "sg"). No such thing for pellets. Go back and look at some of Matt Dubber's "Ballistics 101" videos where he talked about the development of the FX STX liners. It seems for pellets you need spin as it leaves the barrel to keep the disturbed air behind it from causing it to get too much out of alignment and bleed a lot of velocity in having the skirt correct alignment by drag. After that, you need very little spin for pellet stability. In fact, too much spin causes spiraling. So, he talked about finding that fine line between enough twist for initial stability but not so much as to induce spiraling. I think this is why the FX Superior STX liners for .177 have a 1:18 twist rate and the same liners for .22 have a 1:24 twist rate. The smaller lighter .177 pellet needs more initial help in stabilizing out of the barrel. Thoughts?

Cheers,
Greg
Click to expand...
If thats true why are most lw barrels in 22 1-17.7? But and its a big 1 best info i have is that brk and daystate 22 barrels are 1-30 and shoot mrds pretty well? And another but is that the current mrds just don’t shoot well at 100 I know from shooting them that the new mrds are better for head size and weight but im still shooting 25 @ 100
 
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NAProf said:
Thank you all for your input!

I tried the tune ViperJoe suggested, and it is much better than where I had been. Even at 150 bar for regulator pressure I was able to shoot 3 magazines before dropping off the regulator. The MRD's were running at an average of 956fps and at 50 yds the accuracy was "much better". I will play with the tune a bit to see if slowing or speeding up 10-20 fps helps accuracy.

Note to elh0102 - I have been doing a little research on twist rates. Pellets are way different than bullets on this. There are well define twist rates to get bullets to "go to sleep" (reach dynamic stability) depending on length, mass, velocity, and caliber (See Bryan Litz's book on applied ballistics about gyroscopic stability factor "sg"). No such thing for pellets. Go back and look at some of Matt Dubber's "Ballistics 101" videos where he talked about the development of the FX STX liners. It seems for pellets you need spin as it leaves the barrel to keep the disturbed air behind it from causing it to get too much out of alignment and bleed a lot of velocity in having the skirt correct alignment by drag. After that, you need very little spin for pellet stability. In fact, too much spin causes spiraling. So, he talked about finding that fine line between enough twist for initial stability but not so much as to induce spiraling. I think this is why the FX Superior STX liners for .177 have a 1:18 twist rate and the same liners for .22 have a 1:24 twist rate. The smaller lighter .177 pellet needs more initial help in stabilizing out of the barrel. Thoughts?

Cheers,
Greg
Click to expand...
Greg, I can't say that I understand the aerodynamics behind your description, but I certainly don't have the experience to doubt it. As I mentioned, I was drawing from my experience in load development and barrel selection in cartridge rifles. That might be a faulty comparison, and I apologize if my suggestion is incorrect.
Ed
 
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Solo1 said:
If thats true why are most lw barrels in 22 1-17.7? But and its a big 1 best info i have is that brk and daystate 22 barrels are 1-30 and shoot mrds pretty well? And another but is that the current mrds just don’t shoot well at 100 I know from shooting them that the new mrds are better for head size and weight but im still shooting 25 @ 100
Click to expand...
Solo,
Thanks, that is good info.

I know that the LW polygonal barrels come with different twist rates than their land/groove barrels. Based on the info I presented the 1:30 twist rates for BRK/Daystate on the .22 MRD's makes sense as it gives a slower pellet spin rps. It seems they believe the heavy, bigger MRD's don't need the additional help right out of the barrel that the .177's do.

At the end of the day .25 is likely a much better choice for 100yds than a .22.
Cheers,
Greg
 
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Hi Greg,

As far as the MRDs, my friend Joe shot a 220 in Sportsman benchrest at NAC last year shooting MRDs at 970fps from his FX Impact. Joe finished third in Sportsman benchrest at NAC this year.

Mark, who won Sportsman 100 Benchrest this year with his Thomas rifle told me he was shooting the MRDs at 965fps.

I’ve only tried MRDs once at 100 and results were average at best shooting them at 900-915 fps. The results were excellent at 75 and 80 yards shooting the MRDs at 900-915 fps. So, it seems that something happens in the last 20-25 yards to throw them off if shooting below 965-970 fps.

-Ed
 
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EPG said:
Hi Greg,

As far as the MRDs, my friend Joe shot a 220 in Sportsman benchrest at NAC last year shooting MRDs at 970fps from his FX Impact. Joe finished third in Sportsman benchrest at NAC this year.

Mark, who won Sportsman 100 Benchrest this year with his Thomas rifle told me he was shooting the MRDs at 965fps.

I’ve only tried MRDs once at 100 and results were average at best shooting them at 900-915 fps. The results were excellent at 75 and 80 yards shooting the MRDs at 900-915 fps. So, it seems that something happens in the last 20-25 yards to throw them off if shooting below 965-970 fps.

-Ed
Click to expand...
ED,
Good info. I will have to have a conversation with you about your experiences with the 100yd BR at NAC :giggle: . I tried ViperJoe's tune and I can get them to fly at those speeds. I need to tweak the tune a bit to close the ES and find the best groupings, but it was giving pretty good results (MOA groups for 4 of 5 shots) for 50 yds.
Cheers,
Greg
 
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