Will a lead ball .010 under bore size obturate to

[Leatherbark]

the size of the bore upon firing?......I have been shooting my Jackie Brown Carolina smoothbore recently with 70gr of 3fg Black a nitro wad ,crisco lubed fiber wad and a .610 buffalo brand swaged round ball with an overshot wad to hold it in...........With consistant aiming it will shoot under 3 inches at 50 yards........I tried a group at 100yards but mirage was so bad from barrel heat that the group size was around 8 inches.FWIW this load chronographed 1260fps from the 42 inch barrel........The main problem with grouping is how much barrel to look over when sighting........Have any of you ever recovered a bare shot ball from a soft medium and did it look like it obturated?.............Thanks

 

[Rebel]

If you can consistantly shoot 8" groups at 100 yds with that smoothbore, i wouldn't mess with a thing, or worry about what the balls are doing in the bore. Sounds like ya have a real shooter there.

 

[musketman]

If the ball is made of pure lead, it should obturate easy, but you could run into the problem of leading the barrel...

 

[roundball]

Have any of you ever recovered a bare shot ball from a soft medium and did it look like it obturated?

Never shot a "bare ball"...however, I've recovered patched round balls after penetration tests through jugs of water, and I've recovered them from deer I've shot through the heart, etc

I couldn't mic them for 'roundness' of course as they were pushed out of shape, however, the surface of the balls have always been smooth, no land marks, and no patch material weave marks to indicate they had obturated wider that their normal caliber size.

So, I still need some convincing that round balls obturate...or at least in any measureable amount...if they did, it seems that any obturation would change their shape from a "round sphere" to some sort of other shaped object.

Seems if they go wider from obturation I'd see marks...and... wouldn't they would become correspondingly shorter, and probably affect accuracy as a result. ::

:m2c:

 

[Java Man]

RB,

I've recovered one ball from a deer. It did have patch weave marks on it. It was a .50 cal. For some reason the .58's just buzz right on through. :winking:

Gregg

 

[rmonday2]

It would seem to me that it takes more presure to start the ball into the muzzle than it yould to push it back out, and besides that, the presure on the sphere would be eaquil at all points preventing the deformation of any kind. :agree: with roundball on this one :m2c: Ronnie...

 

[roundball]

RB,

I've recovered one ball from a deer. It did have patch weave marks on it. It was a .50 cal. For some reason the .58's just buzz right on through. :winking:
Gregg

Yeah, my .45s & .50s usually stop under the far side hide....54's & 58's are pass-thru's.

I just use standard nominal size balls (440/490/530/570)...and one of my TC .50cal barrels will show a pillow ticking weave just from seating then pulling a ball, but the .45/.54/.58's are not that tight.

 

[jim gray]

I think that if any appreciable amount of obturation occurs that bottom of the ball would be flattened out somewhat and would probably be flattened out to a noticeable extent.

I have recovered a lot of ball from my .36 cal. revolver and the back side of the ball showed no sign of flattening.

 

[silverfox]

IMHO Whats to flatten on a roundball, I don't think physics and shape of the round ball would allow it to flatten. Now the hollowbases and the flat bases both have something for the pressure to work on and both will flatten to fit the bore. :imo:a roundball won't flatten. Look at all the target shooting that has been done and you don't fine funny looking holes with roundball. They don't tumble either. They don't get blown skirts or cut bases. RB they just shoot where to point them.
Fox :imo:

 

[robinghewitt]

If you want it to obturate I think you'll have to put 2 in :thumbsup:

 

[CoyoteJoe]

But how do you know they don't obturate and how do you know they don't tumble? The hole is going to be pretty much round one way or the other, if they do obturate it would be only a matter of a few thousandths and you'd never know it by examining the target.
Unfired balls pulled from the barrel or pushed through an unbreeched barrel show patch weave marks all around the circumference, deep and distinct at the lands, lighter at the grooves. With a tight load there really isn't room for a ball to expand much in the bore but some, maybe.
It isn't bore friction which causes obturation but inertia. The ball tends to remain at rest while the gas pressure is insisting that it move and the ball is squashed between opposing forces, likewise a shot load.
Not saying they do obturate, but with a heavy load I think it likely. As Squire Robin said, load two balls and they dang sure will, so one ball with a heavy powder charge "probably" will. If it makes a round ball into a wadcutter that's too much powder. :crackup:

 

[TFoley]

How can a spherical projectile tumble? Only an elongated projectile, by definition, can tumble about an axis. As a sphere has no elongation, it must simply spin around its axis, induced by the rifling. Or not, if it is a smooth bore.
Round ball certainly elongates when fired from a revolver, as it passes through the forcing cone and into the bore, but, as has been onoted elswhere on this thread, the amount of deformation suffered by a round ball on firing must be micrometric, rather than obvious to the eye, like a revolver bullet is.

tac :grey:

 

[CoyoteJoe]

If a bullet does not rotate around an axis in line with the bore, then it can be said to be yawing or tumbling requardless of the shape of the bullet. With a round ball that tumble is not decernable by the shape of the hole in the target, but may still be happening.
Roundball actually makes a good case for obturation when he stated that balls loaded and pulled from his rifle show no sign of patch weave. How could a ball be spun and stabilized if it does not engage the rifling? Roundball reports very good accuracy from such loads and it would seem that could only happen if the ball does obturate on firing.
:hmm:

 

[roundball]

If a bullet does not rotate around an axis in line with the bore, then it can be said to be yawing or tumbling requardless of the shape of the bullet. With a round ball that tumble is not decernable by the shape of the hole in the target, but may still be happening.
Roundball actually makes a good case for obturation when he stated that balls loaded and pulled from his rifle show no sign of patch weave. How could a ball be spun and stabilized if it does not engage the rifling? Roundball reports very good accuracy from such loads and it would seem that could only happen if the ball does obturate on firing.
:hmm:

Not sure that's what I said at all...

I do not believe any round ball obturation occurs, at least none that is measureable, based upon my recovered balls from water jug tests and dead deer...no patch weave marks and certainly no rifling marks on them whatsoever...and I enjoy excellent round ball accuracy.

The excess patch material wedges down into the grooves (engages the rifling in your post) and is what 'rotates' the patched ball as it moves up bore, giving it whatever spin it's going to get.

If the ball was forced/obturated into the grooves, the edges of the lands would cut the patches to shreds...the ball simply rides on the lands like a train rides on rails.

 

[musketman]

How could a ball be spun and stabilized if it does not engage the rifling?

Not much rifling found in most smoothbores... :haha:

However, in rifled barrels, the ball is spun by a paradox, it receives it's spin from rifling it never touched, the patch transfers the spin to the ball...

 

[riarcher]

My "take" on this is that I doubt that the ball expands in dia. in any way. That's why folks get "blown" patches.
Now if it was a bare ball, .010 under ball, I'd expect some "barrel leading" would show as proof. I've never hear anyone complaining about it, so I assume it just don't happen.
Besides, I'd think the hot gasses from he powder would keep any clearance from establishing with blow-by. :m2c:

 

[robinghewitt]

I do not believe any round ball obturation occurs, at least none that is measureable

I agree. The inertial mass of a ball is concentrated down the centre line of the bore, there is no mass to push against where it touches the bore.

If you crush a lead ball the ends go flat, there is very little increase in girth.

I think a round ball will go egg shaped as the heavy centre line is left behind, but don't worry. I don't expect anyone to agree :crackup:

 

[CoyoteJoe]

:bull:--NO WAY--Musketman, your paradox quotation is from the Lyman Blackpowder Handbook, the same book which shows a drawing of how a "properly patched" ball shows weave marks all around it's circumference. The ball may not touch the rifling but does "engage" it, all-be-it, with a bit of cloth in between. If the ball isn't marked by the rifling, why would it it spin? Seems to me the patch would simply slip around the ball which resists rotation by it's own inertia.
Some folks here seem to respect the opinion of Dutch Shults as to accurate rifle shooting and he insists that obturation is essential to accuracy and for that reason he insists light powder loads won't shoot well, not enough "kick" to cause obturation. I don't always agree with Dutch, I've seen good accuracy with as little as 30 gr. 3f in a .50 cal. But I run tight fitting patch and ball combos which probably don't need obturation.
Some folks seem hung up on the shape of the ball. Shape of the bullet has nothing to do with it. Black powder cartridge shooters all agree that undersize bullets will obturate to bore size when fired. Those bullets are longer and heavier than a ball and therefore have more inertia to oppose the force of the powder gas, thus more obturation, but it would occure just the same if the bullet base were hemispherical.
All this aside, I agree with Rebel, if you're getting good accuracy don't worry about why, just shoot it. ::

 

[smokeblower]

I have several 30-40 round balls dug from the battle of Davis Bridge, from the county I live in, that clearly show smoothed side stablization and expansion. I assumed they were fired from a smoothbore as all the cannon cluster shot-balls, have deep dents and dings from impact with other shot.

 

[roundball]

If the ball isn't marked by the rifling, why would it it spin?

Lead conicals are designed to 'be engraved' by the rifling in a muzzleloader

But roundballs are not designed that way...roundballs are designed so that under all normal, nominal, standard, industry conditions, rifling will not engrave them.

A round ball spins because it is held snugly in a patch which spins.

The patch spins because some of it's material is wedged down into the spiral grooves causing the patch to spin.

The spiral grooves rotate the patch which rotates the ball which is what Musketman was also referring to by the word paradox.
:front: