THAT is why the .22LR uses a 16" twist, not an 18"Bob
Quote from: rsterne on December 12, 2017, 02:06:47 PMTHAT is why the .22LR uses a 16" twist, not an 18"BobCan you explain the 16" vs 18" twist and why 16" is better for .22?Thanks
I do not believe that any pellet is likely to be better at higher velocities.... It makes no sense from everything I have read about Subsonic Ballistics.... either in terms of Gyroscopic Stability, or Dynamic Stability.... In fact both tend to decrease as you get closer to Mach 1.... here is a typical stability curve for a .22LR bullet.... This chart is particularly interesting, because it is in an 18" twist, not the usual 16" twist for a .22LR barrel....The "ideal" stability is about 1.5, like the bullet is when Supersonic.... Anything at 1.0 or below is unstable.... Note that just as the bullet drops through the speed of sound it goes unstable and will tumble.... THAT is why the .22LR uses a 16" twist, not an 18".... For airgun use, we seldom care about what happens below Mach 1, in fact usually we stay below 1000 fps.... Look at the shape of the stability curve there.... As the velocity drops, the stability INCREASES.... We are talking Gyroscopic Stability here - the resistance of the bullet to tumbling.... Airgun pellets follow the same trend, but because of their drag-stabilized (skirted) shape, they can get away with MUCH lower twist rates....Pellets have another problem to deal with, Dynamic Stability, which causes the pellet to wobble, like a Gyroscope does.... This is called Precession and Nutation.... Since the forward velocity of the pellet decays more rapidly than the RPM, as the pellet travels downrange it acts like it was shot at a lower velocity with a faster twist rate.... This combination decreases the Dynamic Stablity, and can make the pellet corkscrew or spiral.... A pellet that shoots perfectly out to 50 yards may be useless at 100 yards for this reason.... and yet if you slow the muzzle velocity down a bit, it is fine.... I have never heard of a pellet that is sprialling get better with increased velocity.... IMO, when somebody sees an improvement in accuracy at a higher velocity, it is almost always due to improved barrel harmonics of THAT pellet in THAT barrel.... and has nothing to do with pellet stability....Bob
IMO they have a place in .22 cal PCPs that are over 40 FPE.... and better at 45-55 FPE.... The 18.1 gr. Heavies are such a great pellet, and they shoot lights out for me at 960 fps.... why would I look for heavier and slower in a 37 FPE gun?.... I had one gun that liked the old Monsters, my B-51 tuned to 50 FPE.... other than that they were mediocre accuracy.... I'm hoping the redesigned ones will be better.... Eventually they will show up in Canada and I will find out....Bob
Quote from: rsterne on December 19, 2017, 12:03:48 AMIMO they have a place in .22 cal PCPs that are over 40 FPE.... and better at 45-55 FPE.... The 18.1 gr. Heavies are such a great pellet, and they shoot lights out for me at 960 fps.... why would I look for heavier and slower in a 37 FPE gun?.... I had one gun that liked the old Monsters, my B-51 tuned to 50 FPE.... other than that they were mediocre accuracy.... I'm hoping the redesigned ones will be better.... Eventually they will show up in Canada and I will find out....BobI think part of it is the name. I'm shooting the MONSTERS just sounds more powerful . I bet many people are shooting these in guns that would be better off with the 18gs but the 18s just don't sound as POWERFULL as "I'm shooting the MONSTERS" !!!!
Quote from: Ribbonstone on December 13, 2017, 06:48:36 PMAs to the Rabbit MAgs.(I or II): PASS.22 Rabit Mags (I or II) have been pretty horrible for me. Tested soemthing like 7 or 9 .22 PCP's at various power levels (most are mine..a couple were borrowed) from 12 to 52 foot pounds.Did find one that did do "ehhh"....but it was good enough to usefully to about 25-30 yards...so use the last of those tins up in that rifle.Now the "why" that one barrel/rifle shot them well enough to use escapes me....just part of the general "independence" of PCP barrels. It's not the fastest or the slowest (running about 25 foot pounds...which with these pellets, is pretty much just loafing around in speed)....certainly not the most expensive....and certainly not what I expected.I would just about that the bbl. is either very lightly choked, or none at all. That, or the rabbits just happen to match the choke. This would be very typical in bullets in ag barrels. Knife
As to the Rabbit MAgs.(I or II): PASS.22 Rabit Mags (I or II) have been pretty horrible for me. Tested soemthing like 7 or 9 .22 PCP's at various power levels (most are mine..a couple were borrowed) from 12 to 52 foot pounds.Did find one that did do "ehhh"....but it was good enough to usefully to about 25-30 yards...so use the last of those tins up in that rifle.Now the "why" that one barrel/rifle shot them well enough to use escapes me....just part of the general "independence" of PCP barrels. It's not the fastest or the slowest (running about 25 foot pounds...which with these pellets, is pretty much just loafing around in speed)....certainly not the most expensive....and certainly not what I expected.
Hi Bob:I don't know why, but I am not getting your pic. Only the dreaded tiny square in the top left corner.Opened in a new tab, and Photo B. started loading the pic, then it instantly went to a blank square int the page, again with the tiny square in the top left corner of what should've been a picture. GRRRRR!!!Knife
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