Well, have to point out again ... the faster they went, the better they did, at least till the 1040 area. Can't blame trans sonic shock on all that.
Bob
Bob
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How to tell if a pellet is over or under spun?
- Thread starter Arzrover
- Start date
The transonic thing is one event - pellets obviously weren't designed to "transition" (word from the ELR powder burner world). Projectiles behave differently when they have to "transition", and this can result in unpredictable ballistics. Best to avoid having your pellet transition.
The twist rate thing is interesting. My ballistic knowledge comes from the "powder burner" world, which is not necessarily apples to apples with diabolo pellets. You can't really over spin a rifle bullet - not in a stability sense. A projectile can be overspun to the point where the jacket may separate, or the core becomes deformed, which obviously will have negative impact on ballistics. But generally, it's better to spin faster then slower, as long as you aren't damaging the projectile.
Out of my .22 Taipan Veteran long, I can shoot slugs and 18 grain JSB's to targets out to 273 yards (farthest I've gone so far), with predictable results. The RD Monsters are something else, and I don't think they are getting twisted fast enough to stabilize once they drop below a certain velocity. I'm not sure what happens if a pellet gets "overspun" (if there is such a thing), but I can't help but wonder if a faster twist barrel would help with the RD Monsters.
RD Monsters shoot excellent at ~10 yards for me. Take them to 120+ yards, and they really start flying unpredictably out of my Taipan Veteran. I recently got a power spring from Talon Tunes, which only added ~30 fps, and I just ordered a power plenum to try and get a bit more power out of my Taipan. This past weekend I shot the RD Monsters at 115 yards, and they worked perfectly for that distance. I want to take them out further again, and see where the threshold is for them falling apart now with my power spring, and soon to be power plenum. With our velocities and twist rates, we seem to be operating on the ragged edge of stability with the RD monsters. The farther out they go, and the slower they get, the closer to instability they become. In my experience, at some point they become completely unstable and unpredictable. Some people just haven't shot them far enough to see that instability.
My theory with the RD monsters is that the CG is further back from the head, with that long skirt design. Having that CG further back makes it act more like a traditional rifle bullet. When it gets to a certain velocity with our slower spin rates, it starts to "wallow" in flight, cutting an elliptical path through the air. It wants to rotate around it's center of gravity, which will cause the nose/head to pitch around more, creating an unpredictable trajectory.
I can't help but wonder if a faster twist rate would help. I believe my Taipan is a a 1:17. I would love to try something like a 1:12 barrel to see if stability improves (or even decreases). I'm not sure where to source faster twist barrels for my Taipan Veteran, but I would love to experiment with this if I could.
The twist rate thing is interesting. My ballistic knowledge comes from the "powder burner" world, which is not necessarily apples to apples with diabolo pellets. You can't really over spin a rifle bullet - not in a stability sense. A projectile can be overspun to the point where the jacket may separate, or the core becomes deformed, which obviously will have negative impact on ballistics. But generally, it's better to spin faster then slower, as long as you aren't damaging the projectile.
Out of my .22 Taipan Veteran long, I can shoot slugs and 18 grain JSB's to targets out to 273 yards (farthest I've gone so far), with predictable results. The RD Monsters are something else, and I don't think they are getting twisted fast enough to stabilize once they drop below a certain velocity. I'm not sure what happens if a pellet gets "overspun" (if there is such a thing), but I can't help but wonder if a faster twist barrel would help with the RD Monsters.
RD Monsters shoot excellent at ~10 yards for me. Take them to 120+ yards, and they really start flying unpredictably out of my Taipan Veteran. I recently got a power spring from Talon Tunes, which only added ~30 fps, and I just ordered a power plenum to try and get a bit more power out of my Taipan. This past weekend I shot the RD Monsters at 115 yards, and they worked perfectly for that distance. I want to take them out further again, and see where the threshold is for them falling apart now with my power spring, and soon to be power plenum. With our velocities and twist rates, we seem to be operating on the ragged edge of stability with the RD monsters. The farther out they go, and the slower they get, the closer to instability they become. In my experience, at some point they become completely unstable and unpredictable. Some people just haven't shot them far enough to see that instability.
My theory with the RD monsters is that the CG is further back from the head, with that long skirt design. Having that CG further back makes it act more like a traditional rifle bullet. When it gets to a certain velocity with our slower spin rates, it starts to "wallow" in flight, cutting an elliptical path through the air. It wants to rotate around it's center of gravity, which will cause the nose/head to pitch around more, creating an unpredictable trajectory.
I can't help but wonder if a faster twist rate would help. I believe my Taipan is a a 1:17. I would love to try something like a 1:12 barrel to see if stability improves (or even decreases). I'm not sure where to source faster twist barrels for my Taipan Veteran, but I would love to experiment with this if I could.
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I hope to see results with more power and higher velocity since you note they did better the faster they went. Assuming that the 1040 was the max you could reach. Always something to learn.
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I've been experimenting with my custom .22 Armada for future long range bench rest. Shooting the 25.39gr RD through a tensioned 700mm FX 20206 slug liner (1:15 advertised twist rate). I'm currently playing with the barrel harmonics (weights and tension). I keep gravitating back to the 1050-1080fps range as it seems the most consistent for 75yd and 100yd. I tried lower velocity (~960fps) but it was not as good. I'll probably shoot it at 1060fps until I exhaust some other variables that might affect accuracy. I can go as high as 1120fps in it's current configuration, but efficiency is not good. It takes a lot of air to keep it at the higher velocities.
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Surprising results in Chairgun??? I wanted to see if the predicted results of a side wind varied enough vs velocity in order to be a bigger variable to group size than any possible spiraling from shooting at over 1,000 fps that some people are getting the best results. I thought that maybe the decreased flight time with the higher velocity would reduce wind drift more than the increased chance of destabilizing. But Chairgun gave me unexpected results where pellets had decreasing wind drift with increasing velocity up to a point. And were then shown to start increasing wind drift again. Entering in different pellets and velocities with a 10 mph, 270* wind selected, some combinations of mass and BC had minimum wind drift at 830 fps. Some had minimum at 900. Above this, all pellets started to be predicted to start having more drift again. ???
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Chairgun is good for comparisons of theoretical wind drift. But what you get in the field can be significantly different.
Chairgun factors in a constant BC for wind drift. But BC is not necessarily constant at all velocities for a given projectile.
https://www.gatewaytoairguns.org/GTA/index.php?topic=14735.msg1265217#msg1265217
A heavier projectile might have better BC when kept above 700fps. If you start out at 830fps for a 100yd target, you'll be way below that velocity before impact. So the BC might be lower than you start with, which results in more wind drift.
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What is puzzling though is, why would Chairgun think that the total wind drift would be more at a muzzle velocity of 1,000 fps than at 830?
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