Yuchi1 wrote:lostknife4 wrote:Yuchi1 wrote:B,
IMO, the gist of the limited material linked, is the rifling stabilized the shotcup and stopped it from tumbling, as contrasted with the smooth bore barrels. With that being said, would it be a huge leap in logic to surmise the straight rifling, as broached into HWL barrels would present a similar stabilizing effect?
First off we have to define tumbling and rotation. There has to be some "stabilizing effect" to a broached or straight rifled bore but just what the parameters of the stabilization is beyond me and I feel there is no requirement for a broached barrel other than the fact that the Wadlock is a much more robust barrel. I think in your friend's case he has not fully analyzed the situation and is thinking 2D when in fact it is a 3D situation. The tumbling or attempt at tumbling is because of this off central axis centre of gravity and the resultant is trying to force the wad to twist sidewise and of course the barrel walls wont allow that but more importantly there is no force making this shotcup rotate about the central or bore axis. Just using common sense he claims approximately 6000 rpm and yet he also claims great patterns from these same cartridges. That is a really obfuscating the facts!
And, like you, would really like to read the article referenced in the footnotes.
BTW, while up on the elevated platform of our wobbletrap house, I have (while coaching young shooters) noticed various shotcups spinning (like a badminton shuttlecock) while flying downrange and yet, others do not spin. Whether those "spinning" shotcups are doing so (or, not) whilst travelling down those particular bore(s) is still a mystery, to me.
These spinning wads are External Ballistics and the forces in play to make these shotcups spin are the air in contact with non symmetrical shotcup petals, this happens all the time and is a well known fact, shotcups outside the barrel can and do spin erratically when they come in contact with the air outside the barrel!
One observation made and is so consistent in repeatability, is that my HWL barrels render patterns that are the most even in pellet distribution (especially with the 20" core) of any barrels I've patterned, to-date and do so with a wide variety of loads.
Is it the broached straight fifling or the heavy barrel that in your opinion is responsible for this? (IMO, the broaching, as with my Remington Premier barrels (which are very robust) the patterns attained (with them) were nowhere near the quality as the HWL barrels)
I have found (steel shotshells) that the factory HWL tube in IC is very appropriate in field use out to 45-50 yards with small(er) pellets launched at high (1550FPS/MV) velocity. The Kent Fasteel load in 2 3/4" with 1 1/16 oz. of #3's @1550FPS/MV is one that fits this bill, as demonstrated (to me) in multiple field instances. Have noted such results with both the 24" HWL barrel aboard one of the 870WM's as well as the 30"HWL on one of the 1100's so, barrel-to-barrel, gun-to-gun, an unmistakable consistency was observed with HWL barrels.
I have been pondering a sort of "test" on this spinning payload situation. Using one of my "old" 30" trap barrels (polished out to remove any residue) and a handload of 15gm/cc tungsten w/o any shotcup (or, a thin, lead load one) fired down the bore (1X) and checked for scoring marks with said measured at both the forcing cone and at the muzzle for any change in attitude to the barrel's axis, to see if there's a difference as this would suggest a rotation of the payload while moving down the barrel. The tungsten would leave rather significant marks as (at, 15gm/cc) it would be ~200DPH vs. the 120DPH of a typical shotgun barrel.
My question (aside from sacrificing a barrel) is would such a test be somewhat moot when you consider the material differences between a plastic shotcup and 15gm/cc tungsten? Is there some method for "marking" a shotcup to where it would leave a "trail" from where it travelled down the bore of the barrel?
Since I have already accomplished this scratch job you can take it from me and several others who have also attested to the fact that the scratches are straight down the barrel add to that the myriad of video's on line showing the shotcup leaving the barrel with absolutely no spinning whatsoever. Why ruin a perfectly good barrel but then again who knows this form of broaching may be beneficial because taken to the extreme isn't that what a Wadlock barrel is? (Say I do conduct such an experiment and find the scoring is off-axis by ~1mm from forcing cone throat to the muzzle, what level of possible (RPM's) rotation would such indicate in a 30" barrel with ~26.5" of total payload contact area?
Redneck engineering at it's finest....
Let's ditch this "RPM" business. It is a unit that was designed for a completely different type of physics. What bullet fired from a gun is in the air for more than a minute? Why do minutes matter in guns? Ned himself threw that out there and it's not a helpful unit for his case. Rifling uses twist rate as it isn't dependent on time or velocity; maybe we should be taking in these terms or something like it.... or at least in terms of radians or degrees per inch (or per foot) or even per millisecond if velocity is a factor in this scenario... which I don't know, does a faster load rotate more than a slower one???
6000 rpm would be maybe 2 full rotations in the barrel before exiting... depending on the velocity and length of barrel.
An off balance load could not rotate more than a half turn as gravity will keep the heaviest part of the load at the bottom edge of the barrel upon enough loss of friction that anything rotates at all.
The chaotic forces of conservation of momentum happening within the shot-cup.. very same that prevent us from using steel in lead loads, would indeed also( to a degree) be translated into some rotational force. This, my friends.. is a more plausible cause for any rotation. If it so happened that more pellets smashing into each other created force in one radial direction than the opposite, the shot cup would turn!!!!! The chances of this?? One in a billion... or so. But I'm just guessing.
This hypothetical rotational force would have to outweigh the perpendicular and tangent forces exerting pressure on the barrel, which increase friction.