Vmax to make a PRB skid/slip across the rifling?

[Greenjoytj]

Has a maximum velocity been tested for that would cause a PRB to loose its grip in the rifling grooves and start to skid across the lands, call it Vmax.
No doubt that a tight or loose fit of the PRB to the bore will change the potential Vmax slip point in the same barrel and rifling twist rate.
Not sure how a person would run such an experiment to test for Vmax. Maybe look at the velocity the group on target starts to show flyers or just balloons abnormally large or maybe the recovered fired patches appear more damaged or shredded than usual.

 

[cositrike]

Has a maximum velocity been tested for that would cause a PRB to loose its grip in the rifling grooves and start to skid across the lands, call it Vmax.
No doubt that a tight or loose fit of the PRB to the bore will change the potential Vmax slip point in the same barrel and rifling twist rate.
Not sure how a person would run such an experiment to test for Vmax. Maybe look at the velocity the group on target starts to show flyers or just balloons abnormally large or maybe the recovered fired patches appear more damaged or shredded than usual.

That’s an awful lot of testing, for something I can’t see as I need to know. Once I’ve worked out an accurate load for a particular rifle, why would I want to know how much powder I have to put in to make it inaccurate? No offence intended, but I just can’t see the need for such tests.

 

[Black Hand]

Has a maximum velocity been tested for that would cause a PRB to loose its grip in the rifling grooves and start to skid across the lands, call it Vmax.
No doubt that a tight or loose fit of the PRB to the bore will change the potential Vmax slip point in the same barrel and rifling twist rate.
Not sure how a person would run such an experiment to test for Vmax. Maybe look at the velocity the group on target starts to show flyers or just balloons abnormally large or maybe the recovered fired patches appear more damaged or shredded than usual.

This seems unimportant, since accuracy/precision would likely have diminished long before this velocity is achieved. And ultimately, since accuracy & precision are primary considerations when shooting, why would this hypothetical "value" be important to know?

 

[Britsmoothy]

Really, do we really need to do this?

 

[azmntman]

This seems unimportant, since accuracy/precision would likely have diminished long before this velocity is achieved. And ultimately, since accuracy & precision are primary considerations when shooting, why would this hypothetical "value" be important to know?

Hmmmm....? Under some administrations this may fit the bill exactly to be awarded a $125,000,000.00 grant to study.

I gotta say I agree, no need to do a test for a result that would never be needed?

 

[smo]

I’m not sure that could happen without causing damage too the patching material first...

If it did “skid” across the lands, wouldn’t it be similar to a ball being shot from a smooth bore gun?

 

[Carbon 6]

If you have rifling engagement upon loading, at what point does it become disengaged ?
Does the spin imparted upon the ball stop ?
Why did the ball begin to skip in the first place ?
Is velocity the true culprit ?

So many questions to answer.

 

[Britsmoothy]

If you have rifling engagement upon loading, at what point does it become disengaged ?
Does the spin imparted upon the ball stop ?
Why did the ball begin to skip in the first place ?
Is velocity the true culprit ?

So many (useless) questions to answer.

Fixed that for you.

B.

 

[Carbon 6]

Fixed that for you.

B.

Thank you.
Who needs rifling anyway, right Brit?

 

[longcruise]

Really, do we really need to do this?

Probably not for smoothie shooters.

Maybe the initial hypothesis that round balls skip the lands is erroneous. It's commonly posited on the internet but who has ever shown for sure that it happens?

I think is just one of those conventional wisdoms that seem probable when thinking about it but maybe just not so. Lots of that stuff in the ml world.

 

[Britsmoothy]

Thank you.
Who needs rifling anyway, right Brit?

Nothing wrong with a rifle brother.

 

[smo]

The only time I’ve ever heard of a ball slipping , skipping or skidding past the lands was in a bulged barrel.....until now.

But you never know until you ask.

 

[FishDFly]

Some folks for look for things to worry about when there is nothing to worry about. Keeps them busy and practicing their typing skills.

 

[Tom Compton]

If you have rifling engagement upon loading, at what point does it become disengaged ?
Does the spin imparted upon the ball stop ?
Why did the ball begin to skip in the first place ?
Is velocity the true culprit ?

So many questions to answer.

Then a .50 caliber barrel with 1/18 twist and .004” deep button rifling can be loaded with a .490 ball and .010” patch over 100 gr of fffg won’t strip the rifling? This information should be shared with the serious competition shooters.

 

[tenngun]

I understand, but have not reshearched it, that the big bore African doubles were made smooth since the big ball could strip the rifeling. Even when made in the belted ball.
I would wonder if it wasn’t mass related and not velocity related. A four to eight ounce ball may resist the spin(???) I don’t know.
I would think your groups would open long before a tight load ‘stripped’ again I don’t know.

 

[FishDFly]

I understand, but have not reshearched it, that the big bore African doubles were made smooth since the big ball could strip the rifeling. Even when made in the belted ball.
I would wonder if it wasn’t mass related and not velocity related. A four to eight ounce ball may resist the spin(???) I don’t know.
I would think your groups would open long before a tight load ‘stripped’ again I don’t know.

Selous in "A Hunters Wanderings in Africa", talks about his help loading for him, throwing handful of powder down the barrel and loading on the run while running after an elephant. See no reason for rifling since shots were very close and accuracy was not an issue at 15 yards or so.

 

[Carbon 6]

Then a .50 caliber barrel with 1/18 twist and .004” deep button rifling can be loaded with a .490 ball and .010” patch over 100 gr of fffg won’t strip the rifling? This information should be shared with the serious competition shooters.

I missed the question mark.......

 

[Black Hand]

We can all agree than our job as a shooter/hunter is to put our roundballs on target fairly close to where we are aiming and that this goal suffers by overloading the gun. As such, I'm still wondering why it is important to know at what point this might happen (even hypothetically)? It serves no real purpose and has no bearing on a practical application...

 

[tenngun]

In the old daysshots were pushed past ranges we use today. Two and three hundred yards shots are recorded in history, and even the worlds military during the smooth bore days experimented out to three hundred yards.
No matter how fast you push around ball at the muzzle it will go subsonic at about one hundred yards. A .50 fired at 2200 FPS will slow to 1100 FPS at a hundred yards. While the same ball shot at 1100 FPS will slow to about 800 FPS at the same range. ‘Magnum loads’ just don’t pay off down range.

 

[Zonie]

Has a maximum velocity been tested for that would cause a PRB to loose its grip in the rifling grooves and start to skid across the lands, call it Vmax.
No doubt that a tight or loose fit of the PRB to the bore will change the potential Vmax slip point in the same barrel and rifling twist rate.
Not sure how a person would run such an experiment to test for Vmax. Maybe look at the velocity the group on target starts to show flyers or just balloons abnormally large or maybe the recovered fired patches appear more damaged or shredded than usual.

I can't answer your question but I have no doubt that under some conditions a patched ball can loose its grip and jump over the rifling grooves.

My Schuetzen is a fine example of this.
The barrel was made to shoot paper patched bullets. It is a .40 caliber with a 1:18 twist and the rifling grooves are .0015 deep.

Although it shoots paper patched bullets exceptionally well, they are expensive so I wanted to try shooting some patched roundballs in it.

Using .395 diameter lead Hornady balls I found the rifle couldn't make a group smaller than 4 inches at 50 yards and I tried a bunch of powder loads and different thicknesses of patches. Nothing worked and the shot patches did look very tattered where the ball squeezed them against the bore.
Like I say, I have no doubt that all combinations of powder/ball/patches will suffer in this gun from your "Vmax".