Pellet corkscrewing

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Ginuwine1969

Ginuwine1969

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Jun 28, 2015
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California, United States
Hey Airgun family, I'm a long time member but just got another scope cam after years without one, and what have I discovered?? My FX MK2 impact .25 cal 600mm Slug A barrel cause not only my MK1 JSB pellets to spiral at 850-920 FPS (it may do it all the time don't know. But my JSB kings also spiral at between 825-920 FPS (that's the range of my power wheel max thru min with Regulator set at 115 bar and Valve spring at 4.1. Can I get some assistance please. I've already cleaned my barrel twice. Swapped out my Donny Moderator for a Huggett still no joy. CANT shoot at the house without one, any other suggestion? Group sizes at 50, 75, and 100 maintain 2 MOA or less. Know it will be better if i get the corkscrewing to go away.
 
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If it is a slug barrel is it possible the twist rate is higher than is acceptable for the pellets? I think spiraling might be a sign that they spinning too fast relative to their forward velocity. My understanding is that slug barrels generally have a higher twist rate, although I don’t know anything about the FX platform specifically.
 
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Have you tried changing the speed? like minus 50 and plus 50 fps if that would change the spiralling behaviour?
I have the same problem with my Leshiy2 with aftermarket Ru*ian polygonal barrel. I have no camera but occasionally I can see that spiralling in the flight depend how the light is coming which side. Also I cannot tighten the groups it looks like pellets tumbling.
My Impact MK2 is tuned for slugs for this season, but I have also the JSB mk1's and mk2's sitting in my drawers for the next setup.
 
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Ginuwine1969 said:
Hey Airgun family, I'm a long time member but just got another scope cam after years without one, and what have I discovered?? My FX MK2 impact .25 cal 600mm Slug A barrel cause not only my MK1 JSB pellets to spiral at 850-920 FPS (it may do it all the time don't know. But my JSB kings also spiral at between 825-920 FPS (that's the range of my power wheel max thru min with Regulator set at 115 bar and Valve spring at 4.1. Can I get some assistance please. I've already cleaned my barrel twice. Swapped out my Donny Moderator for a Huggett still no joy. CANT shoot at the house without one, any other suggestion? Group sizes at 50, 75, and 100 maintain 2 MOA or less. Know it will be better if i get the corkscrewing to go away.
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MrP said:
If it is a slug barrel is it possible the twist rate is higher than is acceptable for the pellets? I think spiraling might be a sign that they spinning too fast relative to their forward velocity. My understanding is that slug barrels generally have a higher twist rate, although I don’t know anything about the FX platform specifically.
Click to expand...
Twist rate is 1:20 and numerous test have been done by Ted B and Matt D as well as this pages moderator and all have conclude that it is not a problem. But thanks.
 
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bigHUN said:
Have you tried changing the speed? like minus 50 and plus 50 fps if that would change the spiralling behaviour?
I have the same problem with my Leshiy2 with aftermarket Ru*ian polygonal barrel. I have no camera but occasionally I can see that spiralling in the flight depend how the light is coming which side. Also I cannot tighten the groups it looks like pellets tumbling.
My Impact MK2 is tuned for slugs for this season, but I have also the JSB mk1's and mk2's sitting in my drawers for the next setup.
Click to expand...
Yup 825-920 no help and these pellets are famous for 880-900.
 
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I’m my katran I was shooting Crosman hps at 930 and the corkscrews accuracy was spot on. Zero at 25 it would shoot at 1 o’clock but under and inch at 35 go to 50 it was back to the 8 o’clock position. When I shot at black background I could see them up and out in a crock screw I dropped the speed to 800fps it was normal drop no left and right.
In the tiapan vet I had shooting the jsb RS at 900 they would do the same spiral. Dropped them to 800-820 and it was a laser. Only 2 guns I’ve had this happen with.
 
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d3vnull said:
Have you pushed a pellet through the barrel? I have no idea if an FX barrel has a crown on it, but a bad crown or something in the barrel that makes the pellet no longer uniform can cause spiraling.
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No have never pushed a pellet thru the barrel, if I do what will I be looking forward? Will it be obvious to the untrained eye? Thanks.
 
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Bander124 said:
I’m my katran I was shooting Crosman hps at 930 and the corkscrews accuracy was spot on. Zero at 25 it would shoot at 1 o’clock but under and inch at 35 go to 50 it was back to the 8 o’clock position. When I shot at black background I could see them up and out in a crock screw I dropped the speed to 800fps it was normal drop no left and right.
In the tiapan vet I had shooting the jsb RS at 900 they would do the same spiral. Dropped them to 800-820 and it was a laser. Only 2 guns I’ve had this happen with.
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i can give 800 FPS a shot, just feel like that is really slow for a 25-33 grain pellet shooting out to 100 yards. But open to suggest. Thanks.
 
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Ginuwine1969 said:
No have never pushed a pellet thru the barrel, if I do what will I be looking forward? Will it be obvious to the untrained eye? Thanks.
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Feel for tight and loose places in the barrel. If the barrel is choked it will be tighter toward the end normally

Look for none uniform rifling groves, deformed skirt, or gouges in the pellet.

Use a wooden dowel to push with
 
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Have you cleaned the new liner? Some barrels/liners have quite a bit of gunk in them. Could it possibly be in backwards?
Just spitballing trying to help figure it out.
My r5m spiraled really bad with H&N hunter extremes, but it was consistently hitting the same spot. They just didn’t agree with the gun, it loves the hades, polymags and mk2 heavies. Might try some H&N barracuda or a different ammo…..maybe slugs
 
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I assume you are getting reasonably consistent velocities. Given the range of speeds and the pellet weights you have tested, it seems apparent to me that the problem, one way or other, is the barrel (in your case, liner). I'm not a slug shooter, but it seems to me, if a barrel is optimized in twist rate and land profile for slugs, it will not be optimum for pellets. But, I'm speaking from a wealth of ignorance, since I don't shoot slugs. As mentioned above, there are other potential issue that could be present in your liner. I would try another one. If you have a bad liner, they should exchange it.
 
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Cranky1 said:
Have you cleaned the new liner? Some barrels/liners have quite a bit of gunk in them. Could it possibly be in backwards?
Just spitballing trying to help figure it out.
My r5m spiraled really bad with H&N hunter extremes, but it was consistently hitting the same spot. They just didn’t agree with the gun, it loves the hades, polymags and mk2 heavies. Might try some H&N barracuda or a different ammo…..maybe slugs
Click to expand...
Yeah i cleaned it twice in the last month, never knew it was spiraling until I got the scope cam, just assumed it was flyers. Sometimes I get sub MOA at 5 yards and other times not. I will try swapping out to the O.G. smooth twist barrel and see what that does. I have some old ones laying around, just have a tough time getting the liner out. :-(
 
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Try checking your magazine, breech, & transfer port in the barrel for any misalignment, debris or burr that might be damaging pellets when chambering. Anything in the entire pellet travel path where damage may be occuring.

Aha...this is covered nicely with great pictures (except for checking all the magazine chambers and fit) in @nervoustrig 's excellent writeup. I printed that to PDF for future reference.

Inspect your bolt probe to make sure the nose isn't bent or otherwise not pushing pellets straight in.

Good luck,
Feinwerk
 
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