The Curse Of The Sprue

[chiller]

I was going over some old Muzzleloader mag's and in May/June 1998 issue there is a article by Darwin Johnston tilted "The Curse Of The Sprue." In it Darwin talks about the fact that the sprue on lead balls is a "Significant blemish on the surface of the ball that can seriously affect the location of the center of gravity, hence its balance, and consequently its accuracy." Darwin goes on and talks about why the sprue causes the lead ball to become unbalanced. As the ball rotates in the riffling and exits the barrel, this spiral action on the ball speeds down range with a unbalanced center of gravity (c.g.) will depart on a path tangent to the spiral. This tangential, a lateral departure from the center of the bore, influences the accuracy of the shot. Daren gives an example, "Using a rifle having a 48-inch twist and seated cast ball with its c.g. located at a distance from the center of the bore equal to the thickness of a piece of paper, 0.004 inches, the ball can be expected to strike no closer than 1.88 inches to an target 100 yards away." Stated more dramatically, Darwin states that this unbalanced ball will strike on the circumference of a 3.76-inch diameter circle centered on an aiming point 100 yards away. Also, patching, starting and ramming inconsistencies can affect the c.g. by as much as 0.015 inches from the center of the bore. Darwin goes into much math with "tables of predicted errors" and gives two conclusions. First, is having a rifle with a slow twist rate and states that "Perhaps this is why we often refer to rifles having a slower twist rate as ball guns," Second, given a choice, use cold swaged balls, or carefully trim the sprue from smooth, round cast balls before using them. After reading this article, my question is, what would you use to remove the sprue, a file, knife, etc?

 

[rodwha]

I’ve read of people using case cleaners. I just use Lee RB molds since they have almost no sprue

 

[rodwha]

I’ve also read of people placing them in a can and tossing them in the bed of the truck for a bit. The rattling and rolling does the same thing they’ve said.

 

[chiller]

Many years ago, at a black powder store that closed a long time ago, sold a wooden round box that the top could move up/down for different diameter round balls with a handle on top and you could load several balls into and rotate the top and would slowly round-out the balls and remove the sprue. Never purchased one since it look like it took a long time and added slightly to the diameter of the finished ball.

 

[Sidney Smith]

I dont notice enough of an accuracy issue to give it any real thought. If I was a competition shooter, maybe Id fret over it, but since Im not I dont worry about the sprue.

 

[chiller]

I dont notice enough of an accuracy issue to give it any real thought. If I was a competition shooter, maybe Id fret over it, but since Im not I dont worry about the sprue.

Yes, but what is the best way to remove the sprue if you want to?

 

[BigSkyRambler]

Yes, but what is the best way to remove the sprue if you want to?

Buy some Brownells "Sprue Be Gone." Works great!

 

[ohio ramrod]

I have two methods for "rolling" balls to remove sprues. The simple on is to roll the balls between two steel plates with spacer blocks the size of the ball minus two thousands. Example .438 spacers for .440 balls. I use a figure eight motion. The other method is to roll the balls between two plates that each have the proper radius in them 1/2 the radius deep. I made these by clamping the plates together and drilling and reaming them centered on the parting line. The first method leaves small flat spots all around the ball which act like the dimples on a golf ball ( In theory) The second method leaves a smooth ball.

 

[Rifleman1776]

He is wrong. The sprue, if loaded very close to top or bottom center, will cause the ball to wobble slightly. But, it will not take it off course. This can be proven by observing the many 50-5X targets at competitions. Sprue can be dealt with but is a pointless effort. Like talking sweetly to a cow while milking her.

 

[FishDFly]

If Darwin really believes the above, he should give serious consideration to cutting his head off. There are some serious similarities between the sprue on the ball and his head, each is a little off center.

 

[EC121]

Many years ago Don Davis wrote a column for some firearm related newspaper that I can' t remember. He was a diehard BP bench shooter at Friendship. His conclusion after testing was that keeping the bottom of the ball round is way more important than any damage to the nose of the ball. Damage to the nose didn't do much of anything, but slight damage to the bottom had a big effect. I don't worry about it.

 

[bang]

Putting the sprue up at center then the pressure put on it at start will flatten the sprue significantly. Put the sprue down will affect the airflow at the back plus there is no way to assure it is in center.

 

[Rifleman1776]

Many years ago Don Davis wrote a column for some firearm related newspaper that I can' t remember. He was a diehard BP bench shooter at Friendship. His conclusion after testing was that keeping the bottom of the ball round is way more important than any damage to the nose of the ball. Damage to the nose didn't do much of anything, but slight damage to the bottom had a big effect. I don't worry about it.

That is correct. Don was my mentor when I started this game.

 

[EC121]

Boy! You must be old.

 

[DOUBLEDEUCE 1]

After casting, I just put the round balls into a coffee can. It gets rolled around for a couple of minutes and sort of evens things out. I’ve even used canning jars to do the same thing. For the most part, you really have to look for where the spruce was before the tumbling in the can. They also get a bit of a tumble in the bullet bag just through handling, nothing major. I don’t over think the process. I just simply enjoy the hobby.

 

[chiller]

After casting, I just put the round balls into a coffee can. It gets rolled around for a couple of minutes and sort of evens things out. I’ve even used canning jars to do the same thing. For the most part, you really have to look for where the spruce was before the tumbling in the can. They also get a bit of a tumble in the bullet bag just through handling, nothing major. I don’t over think the process. I just simply enjoy the hobby.

Does the diameter of the ball slightly increase?

 

[DOUBLEDEUCE 1]

If the diameter of the ball increases, it would be difficult for me to determine. I have never experienced any difficulty in loading after tumbling the ball. In the tumbling some of the lead comes off... my guess in a powder form. Overall, they are 99.9% + rounded.

 

[mooman76]

Thing is unless the sprue is facing downward, it likely will get deformed when loading. Sounds to me like someone is trying to do allot of math without actually proving he is correct.

 

[Sidney Smith]

My Lee molds produce practically no sprue. My bag molds leave a little nub of lead after cutting the excess off. Loading the ball the short starter usually flattens out any lead that was sticking up, and Im sure the ramrod will finish the job. Again not enough of sn issue to fret over.

 

[Carbon 6]

In it Darwin talks about the fact that the sprue on lead balls is a "Significant blemish on the surface of the ball that can seriously affect the location of the center of gravity,

Bullets are inherently more accurate than balls because they do not have a CG that is centered. The location of the center of gravity of a ball and it's effects are entirely within the realm of the shooter.

When I load a round ball, the sprue is pounded back into the ball and the tight fitting patch constricts the ball deforming it into a slight conical. Firing further deforms the ball as it obturates to grip the rifling. All this enhances accuracy. A perfectly round ball leaving the barrel would not be very accurate comparatively.