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Bert, as you likely know, prairie dogs in West Texas are the available long-range varmints here. And the West Texas winds are rarely calm or gentle. Before the pair of factory six millimeters came out in 1954 (?), the 240 Cobra, 257 Roberts and 25 Neidner were not unheard of here. In a 20 knot breeze, they made more sense than the Swift. The 243 WCF pretty much ran the table when it appeared.
Ron, I’m married to a female of the Central Texas German species and you make a very valid point. You wouldn’t believe how hard it is to get a new rifle into my house. It can take a week of watchful waiting.
- Bill
WACA # 65205; life member, NRA; member, TGCA; member, TSRA; amateur preservationist
"I have seen wicked men and fools, a great many of both, and I believe they both get paid in the end, but the fools first." -- David Balfour, narrator and protagonist of the novel, Kidnapped, by Robert Louis Stevenson.
Zebulon said
I’m married to a female of the Central Texas German species and you make a very valid point. You wouldn’t believe how hard it is to get a new rifle into my house. It can take a week of watchful waiting.
I understand your feelings. Many a firearm has started out on this premises hidden in the garage until the moment is right to introduce it to its siblings in the main house.
November 7, 2015
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Zebulon said
Bert, as you likely know, prairie dogs in West Texas are the available long-range varmints here. And the West Texas winds are rarely calm or gentle. Before the pair of factory six millimeters came out in 1954 (?), the 240 Cobra, 257 Roberts and 25 Neidner were not unheard of here. In a 20 knot breeze, they made more sense than the Swift. The 243 WCF pretty much ran the table when it appeared.Ron, I’m married to a female of the Central Texas German species and you make a very valid point. You wouldn’t believe how hard it is to get a new rifle into my house. It can take a week of watchful waiting.
Even this lifelong bachelor knows to keep an old, especially ugly soft case in your car for smuggling in new acquisitions. She’ll recognize the case and hopefully won’t give it a second thought. 
Mike
November 7, 2015
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Back on topic, Bill, as I may have told you I once had the opportunity to use an “R-word” 700 in 22-250 to turn Nosler 40gr bullets into a gray mist at over 4100fps using the then-new Varget powder. It was on a 100 degree plus day and that may have been a factor. I won’t share that load here as it is a bit over the max loads subsequently published. My (incorrect!) recollection was that I was using early Hornady SX bullets when I observed this phenomenon but I have since recovered my load book and perused my bullet inventory. I know little about this situation but I think “overspin” is a better term than the oxymoron-ish “over-stabilize”. Odd thing about my dabblings with the then-new Varget powder was that my 30-06 really liked it under my favorite hunting bullet and it did well in my brother’s hunting rifle as well. When loads were published (this was before Al Gore let us play on his internet) it was also over max and I had to settle for another load.
Mike
Agree that “overstabilize” is a misnomer and “overspun” is a more accurate label.
At least with modern bullets, I’m inclined to believe that, once spun fast enough to achieve stability, additional radial velocity doesn’t affect accuracy– doesn’t make the bullet start wobbling again — unless the bullet comes apart in flight. Like others commenting above, doubt this could happen with a homogenous bullet.
- Bill
WACA # 65205; life member, NRA; member, TGCA; member, TSRA; amateur preservationist
"I have seen wicked men and fools, a great many of both, and I believe they both get paid in the end, but the fools first." -- David Balfour, narrator and protagonist of the novel, Kidnapped, by Robert Louis Stevenson.
November 7, 2015
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Zebulon said
Agree that “overstabilize” is a misnomer and “overspun” is a more accurate label.At least with modern bullets, I’m inclined to believe that, once spun fast enough to achieve stability, additional radial velocity doesn’t affect accuracy– doesn’t make the bullet start wobbling again — unless the bullet comes apart in flight. Like others commenting above, doubt this could happen with a homogenous bullet.
Bill-
I’d be inclined to agree in theory though my current interest is in homogenous bullets of another era and I can assure you they CAN be overspun.
Mike
November 7, 2015
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Beard? Where can I get that hat?
Mike
Hopefully some of you watched the entire video. At about 12:30 he explains some other very important facts.
Chuck, I for sure did and got some more facts at the end. Generally I/we mostly knew this stuff but used incorrect terminology, etc. He was trying to be very precise and did so well. Now, next time we talk, I likely will revert to wrong terminology again. Good info and good material to add to the discussion. Tim
Chuck said
Hopefully some of you watched the entire video. At about 12:30 he explains some other very important facts.
Chuck, I did tear my eyes away from the beard and watched the clip to the end. Beardo launched one right across my bow and said modern bullets could be overspun and their accuracy would be diminished – groups would open up because the “center of pressure” would change.
What he did not explain is what forces create a “center of pressure” and how a change adversely affects the flight path of the bullet.
If that is a true property of radial dynamics, it should be mathematically predictable. Is there a formula for determining the upper limit of accurate radial velocity for a given bullet shape, weight, and dimension?
- Bill
WACA # 65205; life member, NRA; member, TGCA; member, TSRA; amateur preservationist
"I have seen wicked men and fools, a great many of both, and I believe they both get paid in the end, but the fools first." -- David Balfour, narrator and protagonist of the novel, Kidnapped, by Robert Louis Stevenson.
TXGunNut said
Zebulon said
Agree that “overstabilize” is a misnomer and “overspun” is a more accurate label.
At least with modern bullets, I’m inclined to believe that, once spun fast enough to achieve stability, additional radial velocity doesn’t affect accuracy– doesn’t make the bullet start wobbling again — unless the bullet comes apart in flight. Like others commenting above, doubt this could happen with a homogenous bullet.
Bill-
I’d be inclined to agree in theory though my current interest is in homogenous bullets of another era and I can assure you they CAN be overspun.
Mike
O.K. what in your experience happens when a “homogenous bullet of another era” [cast lead?] Is overspun?
- Bill
WACA # 65205; life member, NRA; member, TGCA; member, TSRA; amateur preservationist
"I have seen wicked men and fools, a great many of both, and I believe they both get paid in the end, but the fools first." -- David Balfour, narrator and protagonist of the novel, Kidnapped, by Robert Louis Stevenson.
Bill,
I believe that a cast (homogenous) bullet can suffer greatly when “overspun” in a fast twist barrel. Tight twist barrels will rapidly and excessively “lead up” when shooting cast bullets. That is the primary reason Winchester intentionally selected a 1:16 twist rate for the 32 Win Special cartridge versus the 1:12 twist used for the 30 WCF. Both cartridges were loaded with nearly identical 170-gr bullets, but the 30 WCF was designed for jacketed bullets only, whereas Winchester specifically marketed the 32 WS as being capable of being loaded with black powder (and lead bullets) just like the 32-40.
Bert
WACA Historian & Board of Director Member #6571L
Maybe we should listen to his Part 2 of this series? I am not a mathematician but your group shape will let you know what the barrel wants. There are about 5 or 6 common group shapes. Most can be corrected by a change in powder charge or by the use of a tuner. When I get time I will look through my notes so I can get the data correct.
Bert H. said
Bill,I believe that a cast (homogenous) bullet can suffer greatly when “overspun” in a fast twist barrel. Tight twist barrels will rapidly and excessively “lead up” when shooting cast bullets. That is the primary reason Winchester intentionally selected a 1:16 twist rate for the 32 Win Special cartridge versus the 1:12 twist used for the 30 WCF. Both cartridges were loaded with nearly identical 170-gr bullets, but the 30 WCF was designed for jacketed bullets only, whereas Winchester specifically marketed the 32 WS as being capable of being loaded with black powder (and lead bullets) just like the 32-40.
Bert
Bert, That explanation makes sense to me, much more than a changed “center of pressure” causing overspun jacketed bullets to alter their flight path. Particularly, given that rifling intended for lead bullets often was cut with deeper grooves, excessive radial velocity would surely weld more lead to the bore from higher frictional heat. Any roughness in the steel caused by black powder erosion over time, would make it worse.
So, you’ve answered the question I posed to Mike, in a manner I can understand and certainly accept.
While I’m sure “proper” rates of twist for lead alloys could be and originally were determined by empirical testing, the calculus was not unknown to 19th Century engineers (particularly the French), and surely somebody devised a workable formula. Does anybody know what it is or where it might be found?
What I’m having trouble gagging down, very possibly through ignorance, is the proposition that modern, homogenous — say, solid copper — bullets are suseptible to a drop in accuracy once a certain radial velocity is exceeded because a shift in the “center of pressure” of the bullet introduces some amount of unpredictable irregularity in the bullet’s flight path. If that is so, what is the relationship between radial velocity and the “center of pressure” ? How does one affect the other?
And lastly, if the phenomenon occurs, isn’t an increase in group size caused by overspinning a solid copper, completely homogenous bullet and so changing its “center of pressure”, just another of saying the bullet has become slightly “unstable?”
- Bill
WACA # 65205; life member, NRA; member, TGCA; member, TSRA; amateur preservationist
"I have seen wicked men and fools, a great many of both, and I believe they both get paid in the end, but the fools first." -- David Balfour, narrator and protagonist of the novel, Kidnapped, by Robert Louis Stevenson.
Chuck said
Maybe we should listen to his Part 2 of this series? I am not a mathematician but your group shape will let you know what the barrel wants. There are about 5 or 6 common group shapes. Most can be corrected by a change in powder charge or by the use of a tuner. When I get time I will look through my notes so I can get the data correct.
Good idea, Chuck. I’m.going to watch the rest of the series to see if I can learn something.
I’d be curious also to learn more about group shapes, even though I’m not a far gone target shooter.
As the late Elmer Keith once said, “Well, I’ll be damned! There’s always somethin’ new to learn, ain’t there?”
He was right, as Elmer often was…
- Bill
WACA # 65205; life member, NRA; member, TGCA; member, TSRA; amateur preservationist
"I have seen wicked men and fools, a great many of both, and I believe they both get paid in the end, but the fools first." -- David Balfour, narrator and protagonist of the novel, Kidnapped, by Robert Louis Stevenson.
Here are my notes. These come from Jack Neary, benchrest competitor and Hall of Fame Member. Remember he is talking about groups like the one Tim Tomlinson shot. Hunting groups will be larger. You have to shoot a lot of groups so you are sure what type you are getting. The first 2 shots will be the best group you shoot. It can’t get better than the first 2. I shoot hundreds of 5 shot groups. A bad group is always my fault. I either didn’t load for the correct weather conditions or I did not control the rifle correctly. I have never shot 10 in one hole as Tim did.
Round group is best.
Triangular group is next best.
Double group is too hot.
One flyer is too hot. Or bad neck tension.
Splatter group is too hot.
Vertical string is too light.
Horizontal string is too light.
Zeb, et al. I have commented (I think) that I didn’t use a chronograph in developing my loads for my bench rest rifle. Rather I started with a ball park amount of powder and watched the groups trying for the round group as Chuck just described. When that was accomplished I concentrated on my form behind the rifle and used slight tweaks of powder charges trying to find the magic charge that worked at least most of the time. I have to remember Chuck also passed on about believing the target!! I don’t think you can push equations and decide the optimum powder charge for a rifle/bullet combo. It milght get you started. Then you go to the range and shoot and shoot and keep track of your groups. Tim
November 7, 2015
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Zebulon said
TXGunNut said
Zebulon said
Agree that “overstabilize” is a misnomer and “overspun” is a more accurate label.
At least with modern bullets, I’m inclined to believe that, once spun fast enough to achieve stability, additional radial velocity doesn’t affect accuracy– doesn’t make the bullet start wobbling again — unless the bullet comes apart in flight. Like others commenting above, doubt this could happen with a homogenous bullet.
Bill-
I’d be inclined to agree in theory though my current interest is in homogenous bullets of another era and I can assure you they CAN be overspun.
Mike
O.K. what in your experience happens when a “homogenous bullet of another era” [cast lead?] Is overspun?
Bill-
I’ve heard it called “stripping” when the surface of a lead bullet is being pushed too hard to grip the lands. The outer surface of the bullet is stripped away and deposited in the grooves and the resulting smaller diameter bullet no longer grips the lands as it continues down the bore. Subsequent rounds add to the problem. Gas checks, certain bullet lubes and harder alloys can mitigate stripping but a traditional lead bullet will never be capable of the same RPM’s of a sturdy jacketed bullet. I seldom push a lead bullet much over 2000fps and I haven’t tried a twist faster than 1:12. I know casters who get well over 2000fps but I don’t like investing in tin, antimony and gas checks if I can avoid it. I don’t have the patience for paper patching and would rather not stray down the rabbit hole of powdercoating for the purposes of this discussion.
Mike
November 7, 2015
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Chuck said
Maybe we should listen to his Part 2 of this series? I am not a mathematician but your group shape will let you know what the barrel wants. There are about 5 or 6 common group shapes. Most can be corrected by a change in powder charge or by the use of a tuner. When I get time I will look through my notes so I can get the data correct.
Maybe so, Chuck. I understand overspin but the “center of balance” concept has escaped me thus far. I think it may be related to ballistic coefficient and I struggle to understand that concept.
Sorry I was a little late to this party, I took advantage of the beautiful Texas weather to gently push some homogeneous projectiles down a 120 year old 38-55 bore.
Mike
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