Sprue cut: Facing which way?

[John Spartan]

Relatively new to the sport but (though decades with smokeless) I have been shooting and having a blast. Really haven’t tried for super duper accuracy yet and just having fun. As my smoothbores are replicas of military weapons I have been using paper cartridges so far.

Before I even rolled my first cartridge I had presumed the flat of the roundball (sprue cut) should be “down” facing the powder. This made sense to me as the outhouse expert on ballistics. Then read from a current “well known” source that the flat should be centered “up” toward the muzzle and have been loading and shooting that way.
Just read a book from the apparent grandfather of the sport (Sam Fadala) who flips the apparent current thinking and states the flat should be facing the powder.

Do we have any real science or thorough testing on which way the ball flat should be facing? Up or down?

 

[TreeMan]

I’ve always centered mine facing up. I’d guess that the trip down the bore what little sprue I have is flattened by the short starter and Ram rod.

 

[oldwood]

I always go sprue up , but many say up or down doesn't matter. What does matter , is , don't put sprue sideways.

 

[John Spartan]

Well it makes sense that a flat spot on a “sphere” would have a effect on flight characteristics. Guess the ultimate question is: Is the effect worth worrying about and, if so, how do you minimize it.

 

[CapPopper]

If it's up and centered at least you know it's centered..... Not sure it matters much but seating the ball usually gets rid of most of the sprue for me anyways

 

[pilot]

Sprue up, said an old timer 60 years ago when I was learning about it. That said, no reason was given at the time and the practice may be wrong.

This was from a target shooter that shot in a club that shot at 100 yards off hand.

 

[Old Hawkeye]

I purposely loaded PRBs with the sprue in every imaginable position & shot them to see if it changed POI to any appreciable level. Didn't seem to matter, but I still load sprue up just "cause". YMMV!

 

[jackpine54]

Sprue up. Not sure it matters but that's what I've always done.

 

[Dude]

I've heard the back side of a bullet has more to do with accuracy than the front side. If the pressure escapes one side sooner than the other it can 'steer' the bullet off course. Would that have any bearing on a round ball?

Another question I have has to do with the sprue. Some molds leave a a more pronounced sprue than others. It has to do with the edge of the sprue hole in the mold - whether it's knife edged or wide. One will leave a flat spot on the ball (knife edge) where the other leaves a pronounced ring. I can see advantages/disadvantages either way. Which is better?

 

[FishDFly]

Wonder how many pages this will go?

 

[Brokennock]

Okay. So, ballistically/aerodynamically you are correct. But, once it exits the muzzle it will turn to its best orientation.
The reason people use sprue up is simply to make sure it is centered. If they load sprue up, especially with a patched ball, they can see the sprue.

I really don't think it matters as long as it isn't sideways and scraping down the barrel wall, but even this may not matter of your sprue is tiny and the ball itself is undersized in relation to the bore by more than the height of the sprue.

I've loaded them both ways.
Sprue up with patched ball, sprue down with wads. Flat cut sprue against a flat felt wad seems to work pretty well.

 

[Brokennock]

....One will leave a flat spot on the ball (knife edge) where the other leaves a pronounced ring. I can see advantages/disadvantages either way. Which is better?

Again, probably doesn't matter.
One thing a lot of people seem to have trouble with when getting into this is leaving their modern thinking behind.
Whether it is a discussion of period correct gear or clothing, or a comparison of shooting component variables, we have a hard time leaving out our modern thinking, knowledge, and "reason."
Muzzleloading and roundballs are in a sense more "forgiving" than modern precision shooting equipment, if one accepts them for what they are and their limitations.

 

[Grenadier1758]

Most of us use a loading rod with a round cavity of the diameter of the round ball. The round cavity will reshape the sprue of a soft round ball to conform to the diameter of the ball.

In some castings as the lead cools after a ball is poured, a cavity forms under the sprue. By having the sprue up, that cavity is centered, more or less, with the axis of the fired ball. The centering of the sprue may minimize the wobble induced by the sprue and the internal cavity. To minimize the effect of a void from casting, it is often recommended to weigh the balls. Good casting procedure will also eliminate the casting voids.

In any event I try to load with the sprue up.

 

[smo]

I prefer sprueless balls but that’s not always possible….

IMHO sprue up makes more sense than down or sideways.
My thinking is as the ball is seated it somewhat flattens any remaining sprue if the ball is softlead..
Loading with the sprue down , I think the ball would leave the bore with the sprue protruding just as it was loaded..
Could this cause a roundball too be less accurate?
Does filing a guns muzzle fractions of an inch shift the impact of the ball?
Would gasses/pressure not cause the same effect on a irregular roundball?

Probably not so much in a rifle, but in a smoothbore…. Maybe.

I’ve always loaded sprue up as well, right or wrong it works for me..

Loading with the sprue sideways, can cause more problems..
Especially in a fouled bore…

 

[Brokennock]

I would think ones patch/ball combo would have to be pretty darn tight for the loading rod to smash the sprue flatter or to match the curve of the ball.
None of my smoothbore loads are that tight.

 

[CapPopper]

I would think ones patch/ball combo would have to be pretty darn tight for the loading rod to smash the sprue flatter or to match the curve of the ball.
None of my smoothbore loads are that tight.

Still waiting on my smoothbore and I could see where there's no reason for a smoothbore ball to be quite that tight but in my .32 the short starter definitely leaves an imprint on the ball and removes the sprue..... Not sure it's better than the sprue but it seems to do 1/4 inch groups at 25 if I do my part

 

[Twowithone]

Sprue up was the way we were taught 40+ yrs ago still doing it that way today

 

[Robby]

I'm waiting to hear back from Phil Niekro.
Robby

 

[smo]

I would think ones patch/ball combo would have to be pretty darn tight for the loading rod to smash the sprue flatter or to match the curve of the ball.
None of my smoothbore loads are that tight.

I was shooting a .648 ball in a .653 bore… unpatched.. after 2-3,rounds if I didn’t swab in dry conditions it did become hard to load.

Im now shooting a .626 ball and 0.0016 patch with good results.. and it loads much easy.

 

[Whughett]

As a shooter who casts and shoot both percussion and metallic IIl make the observation that bullets are cast nose down sprue on the base. And once a round ball is forced into a revolver chamber it’s no longer a round ball. Myself I try not to seat them sideways but other wise don’t give it much thought.