Does it make a difference?

[Robert Egler]

I've been thinking about this from a physics point of view, what is the physics that would cause the ball to increase it's rate of spin?

I think that were actually talking about the wrong rate of spin and that’s causing the confusion.

As the ball leaves the muzzle it will have a certain spin in revolutions per second. Ignore for a moment the revolutions per inches traveled.

By conservation of angular momentum the ball will keep this rate a spin (in revolutions per sec) with a slow decrease due to friction. But that’s the friction of the air perpendicular to the direction of travel. In other words, the friction of the spin, not the drag as the ball travels forward. This friction of spin is small in comparison to the drag on the ball, and the drag on the ball as it travels downrange will have only a very small effect on the rate of spin. BUT the drag will slow the speed of the ball considerably.

At the muzzle a ball shot through a barrel with a 1/66 twist with a velocity of 2200 feet per second will have a rate of SPIN of 400 revolutions per second. It will keep this rate of SPIN pretty much (with a very slight slowdown as mentioned above) until it hits the target.

But the distance traveled in 1 second will decrease significantly as the velocity decreases due to drag.

So if we measure the rate that ball is turning in revolutions per inch (let’s call that the rate of twist) we find that the rate of twist increases after the ball leaves the barrel BECAUSE the velocity of the ball decreases faster than the rate of spin decreases. It’s still turning at 400 turns per second, but it’s traveling less distance in that second, so the ball is spinning faster in relation to the distance traveled, ie, the rate of twist.

For example, consider the same ball we discussed about, 1/66 rate of twist at 2200 f/s at the muzzle. The ball moves 66 inches in the time it takes to revolve once,: 1/66. When the velocity drops to 1900 f/s the ball is STILL turning at very close to 400 rev/s, but now because its velocity is lower it’s only moving forward 57 inches while it makes that revolution, so the rate of TWIST is now 1/57, a faster rate of TWIST than the ball had at the muzzle.

SO, to sum it up, the rate of TWIST in revolutions per inch traveled DOES increase after the ball leaves the muzzle. That's because the velocity decreases faster that the rate of spin in rev/sec. The rate of SPIN in revolutions per second does not increase.

That help any?

 

[chapmans]

Runner,
I get it now sorry if I came accross like an a$$.
It'the distance traveled that changes the twist rate as the velocity drops the rpm does not change as fast generating a higher twist rate.
I was imagining some force boosting the twist rate which is not possible.Guess I'm a little (lot) slow
Longball 58

 

[Dphar]

45-50-54-58. There really is no "right" answer. If you live in the east and want a traditional caliber then anything over 40 is OK as far back as at least 1770. By contemporary accounts few "kentucky" rifles of the Revolution exceeded 30 to the pound (.535+- ball) and some were obviously 42 caliber (surviving rifles). Then as now some liked a smaller ball and some liked a larger ball. .44 and .50 were very common. Thus if I were making a Kentucky it would be a 50. I have 2 in the works right now and both are 50s.
The bigger balls will always work better for most uses but do not expect any magic on deer from any caliber on the 45-58 list compared to the other. The 58 will *probably* average a shorter run than the 50 cal. But I would NEVER put money on any given lung shot deer falling faster because it was shot with any ball in this group. I have seen numerous deer run 200 yards (a matter of seconds at full speed) with shots that should have piled them up pretty quickly with 50s, 54s and some modern stuff.
Last deer I shot was with a .662 ball at about 1450 striking velocity and it made 55 yards with the top of its heart completely gone. The deer was obviously REALLY hurt and did not run normally, but she did run. I have had them run less shot through the lungs with a 50 at near 150 yards. Its the old size of the fight in the dog thing.
The 45 will do well even with light charges at ranges to 50 yards. 60 grains will stretch this to 100 I suspect. Little personal experience. Have not shot a 58 in many years though i have killed deer and antelope with one. The 50 will kill deer to about 150 if placed right. At this point trajectory becomes a factor and in reality shots past 120 yards are risky with any RB rifle, so for DEER there is no great advantage in calibers over 50. The 50 will also kill elk, moose, bufflao and bear. But I would rather have a 62 or larger for these though 2-300 pound bear would be no challenge for the 50 RB.
High impact velocity will reduce penetration. But I have never had penetration problems with any RB regardless or velocity. Nor have I had it divert from its intended path until it was past the vital organs and then only rarely.
They always give adequate penetration for the job. But I do not do "Texas heart shots".
With properly placed shots taken within its range the 50RB will fatally wound anything on the North American continent. But I would not be happy shooting a Gbear with anything under 66. These you want to hurt really bad of the first shot.
Anyone who only hunts animals the size of Mule Deer and smaller really needs no larger bore than a 50 especially in the east.
But if in doubt use a bigger ball. I REALLY like my 66 and will likely hunt with it for everything though I might build one just like it in 54 for deer since I have some neck/back problems. The .662 ball does use up a lot of lead though.
If you want to drop anything in its tracks you will need to shock or otherwise interrupt the electrical system. Given the advance of chronic wasting disease in the west I have no intention of hitting the spine if I can avoid it. I no longer break the spin to quarter deer when butchering either.
Dan

 

[Dphar]

Squirrel Tail's post makes sense. I had not thought of it in this way but yes the turns per inch must increase even if the actual RPM decrease slightly.

Dan

 

[Tom Gauldin]

I agree !!!

 

[Larry Pletcher]

. . . By conservation of angular momentum the ball will keep this rate a spin (in revolutions per sec) with a slow decrease due to friction. But that’s the friction of the air perpendicular to the direction of travel. In other words, the friction of the spin, not the drag as the ball travels forward. This friction of spin is small in comparison to the drag on the ball, and the drag on the ball as it travels downrange will have only a very small effect on the rate of spin. BUT the drag will slow the speed of the ball considerably.

At the muzzle a ball shot through a barrel with a 1/66 twist with a velocity of 2200 feet per second will have a rate of SPIN of 400 revolutions per second. It will keep this rate of SPIN pretty much (with a very slight slowdown as mentioned above) until it hits the target.

But the distance traveled in 1 second will decrease significantly as the velocity decreases due to drag.

So if we measure the rate that ball is turning in revolutions per inch (let’s call that the rate of twist) we find that the rate of twist increases after the ball leaves the barrel BECAUSE the velocity of the ball decreases faster than the rate of spin decreases. It’s still turning at 400 turns per second, but it’s traveling less distance in that second, so the ball is spinning faster in relation to the distance traveled, ie, the rate of twist.

For example, consider the same ball we discussed about, 1/66 rate of twist at 2200 f/s at the muzzle. The ball moves 66 inches in the time it takes to revolve once,: 1/66. When the velocity drops to 1900 f/s the ball is STILL turning at very close to 400 rev/s, but now because its velocity is lower it’s only moving forward 57 inches while it makes that revolution, so the rate of TWIST is now 1/57, a faster rate of TWIST than the ball had at the muzzle.

SO, to sum it up, the rate of TWIST in revolutions per inch traveled DOES increase after the ball leaves the muzzle. That's because the velocity decreases faster that the rate of spin in rev/sec. The rate of SPIN in revolutions per second does not increase.

That help any?

I like your explanation. I saw on the spreadsheet, finally understood that the reason the linear twist increased was because we were dividing up an increasingly smaller velocity.

The man at Sierra sent me the formula for calculating the decay of the spin (rpm). I made a model and sent it back to make sure I did it right. I'm waiting for an answer, but the number looks like it is very small compared to the rpm at the muzzle. so small that we can probably just use the muzzle number for any practical ML calculations.

Your calculations with 2200 fps and 1-66 twist are similar to Example #1 on my spreadsheet.

Regards,
Pletch

 

[Russ T Frizzen]

Buy the .50--with gain twist rifling.

 

[Stumpkiller]

Picture snapping a top between your fingers and watching it smooth out and accelerate in response to the impetus your fingers provided.

I'm sorry. But you'll have to provide some reference or data that in this universe something will increase in speed or acceleration AFTER the driving impetuous or force is removed. I'd like to have that built into my car so I can remove my foot from the gas to accelerate. I have never heard of anything accelerating on it's own. I'm pretty sure that defies all the laws of thermodynamics, also. Certainlty defies the second law of thermodynamics. Where does it gain the necessary energy?

The perpetual motion machine and cold fusion will be next, I'm sure.

When you force a ball tightly into, say, a 1:12" twist and fire it the ball will spin one full revolution in the first 12", once again in the next 12", and so on for the length of the barrel. It is held fast to the rifling. Forward speed increases (until it exits the barrel for practical barrel lengths and powder charges), but twist does not. The twist itself is a constant. It just takes different times to complete that full revolution. And once it leaves the barrel that time steadily increases.

I'll have to go back and retake Physics 161 & 162 if that is not true.

Capt. Vee - buy the .45 OR the .50 and for God's sake shoot it, shoot it well and with enough powder to matter and enjoy it without overthinking the damned thing.

 

[Runner]

Stumpkiller, I don't have to provide you anything. Why is it you keep talking to me when I have plainly told you I am not interested in talking to you? Go away already. I am trying to be polite about it.

 

[Stumpkiller]

Sorry. You can't ignore me 'cause I'm a moderator and I can't ignore you 'cause I'm a moderator. We'll just have to suffer on together.

 

[Runner]

Then talk to me in your moderator role only and leave me alone the rest of the time. Go talk to someone interested in what you have to say. That is not me!
May God give you the best he has for you, but may you enjoy his gifts far away from me.

 

[RC]

Sorry. You can't ignore me 'cause I'm a moderator and I can't ignore you 'cause I'm a moderator. We'll just have to suffer on together.

you two brothers???????? :stir: :stir: :slap:

 

[Stumpkiller]

That would explain why Dad got a Christrmas card from a carnival show every year. :hmm:

 

[Walks with fire]

http://members.aye.net/~bspen/math.html

An interesting read and useful resource.

I think the .50 would be best for deer. If you want to go to .54 or .58 that would be ok too--if your going to load it to it's potential. Better to use full power loads in a .50 than lower loads in the bigger bores.

 

[MrMarine79]

That would explain why Dad got a Christrmas card from a carnival show every year. :hmm:

:rotf: :rotf: :rotf: :applause: :applause: :rotf: :rotf:

 

[nchawkeye]

Dang...94 replys, 1044 views and we're talking about tops, rotations, etc....

Claude must be on vacation... :grin:

Capt...My first flinter was a Bob Watts .45 caliber, I bought it back in the 70s...I killed 25-30 deer with it...With 75grs FFF Goex and a .440 ball the ball would usually end up on the off side, just under the hide and do a decent job on our NC whitetails...It would usually not exit the other side...I did have a couple that went further (125 yards or so) than I wanted them to go...So I was considering a .50.

One morning, I had an encounter with a rather large black bear, at that time, I decided on a .54...I have killed about 30 deer with that and that's what I prefer...I usually get an exit on lung shot deer...

Between a .45 and a .50, I'd pick the .50 for deer...But a .54 is what I prefer for hunting deer...

 

[Runner]

It is kinda funny that one of the mods is breaking the forum rules and nothing is done about it. Maybe Claude is on vacation!

 

[Mike Vach]

Well, after all the talk and all the advice and all the discussions, I bought a .50 cal fullstock Virginia rifle - in flint, of course. What an agonizing decision. The board was pretty well split between the two calibers I was considering, and Paul was even swaying my thinking into a .36 for a while. Then I got to thinking if I bought a new .45 cal, I'd have to buy a new mold, new jags, a new bag to go with it, etc. Now, that's all well and good but if I bought a .50, I already have the accouterments so I can add a little more to my stash and upgrade a little on the gun, if that makes sense. Plus, while I understand that both could kill deer, I'm more comfortable with the .50. And, once I realized I was overanalyzing the whole dang thing, I bought the .50.

Now I have to think of another question to ask you guys that will generate as much discussion. Thanks. It was great. It's a real warm camp. :applause:

 

[Runner]

Congrats! Now you need a 36 to chase squirrels and groundhog with!

 

[nchawkeye]

Can we see some pics???

Then we can "discuss" if it's a "proper" Virginia gun!!! :grin: