Theory of patched round ball load development.

[Ironoxide]

Hi,

I recently re-read James Forsyth "The sporting rifle and its projectiles" as I read it for z very first time some years before and I became interested why is it that muzzloading rifles (specially those shooting patched round balls) are most accurate with one specific powder amount. It is obvious why rifle's accuracy deteriorates when loaded with too much powder. Forsyth talks about it at length. The patch(or the lead) tears in the rifling and skips it resulting in unpredictable rotation.

However, it is not that obvious what happens if we load less than ideal amount of powder. It is definitely a fact prb muzzleloaders will shoot large groups with smaller loads. Then group size significantly tightens when we arrive at the ideal amount.

I observed it in 3 of my rifles. A. 38 cal "squirrel gun", a. 54 cal Pedersoli Pennsylvania flintlock and. 58 double barrel Kodiak. All 3 shot 6-8 inch groups starting with small loads and tightening groups significantly when I arrived at the right load.

I can imagine barrel resonance can have some effect, but not to the extent of 6-7 inch group at 50m tightening to holes touching on the target.

So my question is what is the theoretical explanation behind this? Is there any scientific research that attempts to explain it? Maybe there are other books someone can recommend?

 

[leadhoarder]

I do not think that phenomenon only occurs with patched ball. Modern firearms and ammunition frequently run into the same phenomenon. This is why handloads can perform better than factory produced ammunition.

 

[Jakeytoo]

Spin stabilizes the ball or bullet, increased velocity should ( in my mind ) give you a tighter spin, whereas less velocity will give you a tight wobble ( for lack of better words ).

 

[jdw276]

Get dutch schultz's system. All explained. He is a member here. He has studied this for 50 years and wrote article after article about all this.

 

[yonderin]

My understanding of ballistics is that for max accuracy you need the projectile leaving the muzzle at the same point in barrel harmonics. There are variables that you can play with to achieve this; powder type, charge and grain size, patch and ball combo, lube,etc. Play with them as much you need until you achieve the results that please you.

Dutch's system is very helpful for achieving the minimizing of variables that are under your control. But people will tell you there's more than one way to skin a cat.

To an extent, every gun has it's own personality, what works in one doesn't necessarily work as well in an apparently identical one.

 

[Brokennock]

Don't know.
I had a .45 Caprock that shot great at 65 grains 3f, but equally well at 40 grains 3f, at 25 yards, at 50 yards and beyond the light load went to heck.

 

[Ironoxide]

I do not think that phenomenon only occurs with patched ball. Modern firearms and ammunition frequently run into the same phenomenon. This is why handloads can perform better than factory produced ammunition.

Yes. I focused on patched round ball (and black powder), because I haven't got the experience with nitro hand loads so I don't know the magnitude of "group tightening" usually occuring with the right load.

It is so counterintuitive to me exactly because of the magnitude of the effect. For example my squirrel rifle. On 50m with any load other than 34 grains it produces groups 6 in big. With 34 grains the holes are touching and I feel it shoots better than I can hold it. To go 3 inches to the side at 50m the ball would have to be 60 thou to the side when exiting a (1m long) barrel. 60 thou (1.5mm) seems like a huge amount of flex for a steel octagon barrel. However, maybe that's exactly what happens.

I wish there was some research with super slo-mo footage of the barrels etc.

Spin stabilizes the ball or bullet, increased velocity should ( in my mind ) give you a tighter spin, whereas less velocity will give you a tight wobble ( for lack of better words ).

My understanding of ballistics is that for max accuracy you need the projectile leaving the muzzle at the same point in barrel harmonics.

I think that a "wobble" may be what's happening. It is much easier for me to imagine the spinning of the ball is nudged very slightly by a barrel flexing single thou resulting in a wobble that compounds to the side more and more with each rotation than barrels flexing over a mm to the side.

Don't know.
I had a .45 Caprock that shot great at 65 grains 3f, but equally well at 40 grains 3f, at 25 yards, at 50 yards and beyond the light load went to heck.

Interesting. Maybe it is not a "wobble" that's responsible, but lack of muzzle velocity for adequate spin stabilisation?

 

[LME]

My understanding of ballistics is that for max accuracy you need the projectile leaving the muzzle at the same point in barrel harmonics. There are variables that you can play with to achieve this; powder type, charge and grain size, patch and ball combo, lube,etc. Play with them as much you need until you achieve the results that please you.

Dutch's system is very helpful for achieving the minimizing of variables that are under your control. But people will tell you there's more than one way to skin a cat.

To an extent, every gun has it's own personality, what works in one doesn't necessarily work as well in an apparently identical one.

Your statement ," every gun has its own personality," May be true but I have found that It is rare in my experience. I took three .54 cal.Rifles a C.V.A,Ithaca Hawkin and a lyman and tested them off the bench and using the same load in each of them They all shot identical with the same load and performed best with 80 grains of B.P.. I think that when one finds a weapon that doesn;t seem to shoot as well as another one that is the same that there is a difference of some sort that needs to be addressed. Usually the difference is the sights if where the projectile impacts the target is different but producing a good group? It also could be the one behind the rifle that makes the most difference as well?

 

[LawrenceA]

I believe that consistency is everything. But we must realise that that extends to the shooter and their stance as well as the physical aspects of the rifle and extends to how the powder burns and the bullets velocity and journey. It is well known that the worst consistancy will show on a target where the bullet approaches the speed of sound.
This is ones reason big ol heavy bullets that stay sub sonic shoot so well compared to lighter faster ones.
On top of all that you need enough spin etcetera.

 

[Okie Hog]

i don't have an explanation for it. But much depends on depth of rifling and twist rate. There is a beautiful thing about a slow twist barrel with proper round ball rifling: That rifle puts balls with varied powder charges in the same group.

Was lucky in having a mentor who was a superb marksman, machinist and black powder gunsmith. "Uncle Joe" was over 80 years old when i met him while deer hunting: He lived to 96. Joe had a couple hundred original muzzleloaders in a room off his machine shop: i was told to pick one and he would re-bore it to .50 caliber with slow twist rifling. i selected a nice percussion long rifle with the barrel burst near the muzzle. Rifle was cut down to a half stock with 30" barrel. The twist rate of the finished rifle was 1/92".

Joe was no longer allowed to drive because of too many wrecks. One weekend i took him to a shooting match in PA. Everyone at the match knew him. Some thought he was deceased. One guy said everyone should just go home. Joe won that match and nearly every one we attended.

i have a .58 caliber barrel rifled to my specs by Mr. Hoyt: Twist rate is 1/56". Barrel has rounded grooves and is very accurate with 80 grains of Black MZ powder. 100 grains of Black MZ causes the group to go high right. Dropping it back to 80 grains puts the group in the 3" bullseye at 50 yards.

Next barrel i send to MR. Hoyt will be re-worked to .54 caliber with slow twist, about 1/92".