stubbicatt
New member
We have all probably noticed when firing from a bipod how one leg of the bipod tends to lift free from the ground when discharging a moderate to high recoil impulse rifle. This is a reaction to the rifling imparting spin to a projectile to stabilize it in flight. I don't tend to notice it when firing such a rifle, but see it frequently when watching others do so. I guess I don't notice it when firing as the recoil impulse is strong enough that it masks the torque effect.
I've been shooting a single shot in 32-40 with 200 grain cast bullets in attempt to arrive at a solid load, or load range, for this rifle for 200 yard offhand competition. The loads are target loads, certainly less than 1,500 fps, so recoil is quite mild from a #4 contour barrel. I notice whether shooting from the bench or offhand that the rifle torques noticeably when discharged. I think perhaps the torque perception is magnified by the pronged buttplate as it wraps around the upper arm, and velocities are so mild that they don't mask the torque.
I would say that as I increase charge weights in small increments that I do not perceive any additional recoil, perhaps a more snappy muzzle report, but I do notice torque increasing. This is interesting to me both as a novel experience, and also as food for thought generally, on the topic of rifle accuracy.
It seems reasonable to believe that as either bullet mass or bullet acceleration increases, or twist rate increases, that the torque reaction would also increase, so that a 22 long rifle at 1200 fps in a comparatively slow twist, lighter weight barrel would impart less torque than say a 200 grain bullet in a 300 Win Mag at those velocities. The latter being nearly imperceptible having been lost in the linear recoil impulse that the shooter feels.
I wonder, do you suppose that this torque phenomenon, which must pull the rifle away from the axis of departure while the bullet is still in the barrel, might be detrimental to accuracy, or perhaps impart greater fatigue sooner to the shooter?
I think perhaps this torque phenomenon might account for the comparatively slow twist for bullet weight barrels used by short range bench rest shooters. From what I have read about it, choosing a bullet weight that creeps up on marginal spin stability is very important to them. In essence you won't find a bench rester opting for a 7 twist barrel where a 14 will do nicely, thank you.
In the Schuetzen game this is expressed a little differently so far as I have learned. There the twist rates in 100+ year old barrels are often 16 for 200+ grain 32 caliber cast bullets. With a faster 14 twist barrel one may notice "nose high" bullet strikes on paper, which indicates that one has over stabilized the bullet, and needs to back off the powder charge a little bit, or go with a longer heavier bullet. At 200 grains in a slower 15 or 16 twist barrel, one can maybe get decent spin stability at 1450 fps, but perhaps notice instability at 1400 fps or less. So velocity in balance with twist rate will produce good accuracy due to better bullet stability, and the margins can be very close.
There are guys who are shooting longer, heavier designs, like maybe 206 grain bullets with a different nose profile, who cannot get them to stabilize to their satisfaction in a given twist rate barrel, where a 200 grain bullet will perform better. The differences in bullet length being a tenth or two of an inch. Some even find that gain twist barrels somehow give them a wider range of velocities where stability is assured. I understand that H.M. Pope found gain twist barrels, with left hand twist of all things, would produce better consistency on the target. --Now that one cooks my noodle, but maybe I can think it through.
Ah. Well. Enough. I suppose it isn't good to think out loud on paper like this...
But I feel like there is something for me to learn here, some universal principle that I'm not quite grasping. I know of Greenhill formula and all that reducing this to numbers, but as one approaches the margins of these calculated bullet form mathematical predictions one starts to have to approach the question almost intuitively it seems.
I've been shooting a single shot in 32-40 with 200 grain cast bullets in attempt to arrive at a solid load, or load range, for this rifle for 200 yard offhand competition. The loads are target loads, certainly less than 1,500 fps, so recoil is quite mild from a #4 contour barrel. I notice whether shooting from the bench or offhand that the rifle torques noticeably when discharged. I think perhaps the torque perception is magnified by the pronged buttplate as it wraps around the upper arm, and velocities are so mild that they don't mask the torque.
I would say that as I increase charge weights in small increments that I do not perceive any additional recoil, perhaps a more snappy muzzle report, but I do notice torque increasing. This is interesting to me both as a novel experience, and also as food for thought generally, on the topic of rifle accuracy.
It seems reasonable to believe that as either bullet mass or bullet acceleration increases, or twist rate increases, that the torque reaction would also increase, so that a 22 long rifle at 1200 fps in a comparatively slow twist, lighter weight barrel would impart less torque than say a 200 grain bullet in a 300 Win Mag at those velocities. The latter being nearly imperceptible having been lost in the linear recoil impulse that the shooter feels.
I wonder, do you suppose that this torque phenomenon, which must pull the rifle away from the axis of departure while the bullet is still in the barrel, might be detrimental to accuracy, or perhaps impart greater fatigue sooner to the shooter?
I think perhaps this torque phenomenon might account for the comparatively slow twist for bullet weight barrels used by short range bench rest shooters. From what I have read about it, choosing a bullet weight that creeps up on marginal spin stability is very important to them. In essence you won't find a bench rester opting for a 7 twist barrel where a 14 will do nicely, thank you.
In the Schuetzen game this is expressed a little differently so far as I have learned. There the twist rates in 100+ year old barrels are often 16 for 200+ grain 32 caliber cast bullets. With a faster 14 twist barrel one may notice "nose high" bullet strikes on paper, which indicates that one has over stabilized the bullet, and needs to back off the powder charge a little bit, or go with a longer heavier bullet. At 200 grains in a slower 15 or 16 twist barrel, one can maybe get decent spin stability at 1450 fps, but perhaps notice instability at 1400 fps or less. So velocity in balance with twist rate will produce good accuracy due to better bullet stability, and the margins can be very close.
There are guys who are shooting longer, heavier designs, like maybe 206 grain bullets with a different nose profile, who cannot get them to stabilize to their satisfaction in a given twist rate barrel, where a 200 grain bullet will perform better. The differences in bullet length being a tenth or two of an inch. Some even find that gain twist barrels somehow give them a wider range of velocities where stability is assured. I understand that H.M. Pope found gain twist barrels, with left hand twist of all things, would produce better consistency on the target. --Now that one cooks my noodle, but maybe I can think it through.
Ah. Well. Enough. I suppose it isn't good to think out loud on paper like this...
But I feel like there is something for me to learn here, some universal principle that I'm not quite grasping. I know of Greenhill formula and all that reducing this to numbers, but as one approaches the margins of these calculated bullet form mathematical predictions one starts to have to approach the question almost intuitively it seems.
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