Velocity affect accuracy ?

[Absoroka]

A possible variant might be related to breaking the sound barrier. A round ball is not the most ballistically effective design and encounters significant bow wave issues when breaking the barrier. Shooting velocities that break the sound barrier could happen at different points along the trajectory, depending on the velocity of the load. It could possibly affect POI. That being said, most of us probably can't out shoot the result. My .50 caliber flintlock shoots very accurately with loads ranging from 65 to 110 grains of 2FF. Seventy five grains of 2FF produces the tightest groups most consistently. The search for the "sweet spot" is half the fun.

 

[andy52]

Not bad at all ! If you would put a dot on a blank sheet of paper and adjust your scope left or right off target then shoot a group aiming at the dot you might be surprised at the results. Shooting a small target exactly where you are aiming will destroys your aiming point. That will cause your group to open up a bit! I have won a few dollars with this trick! Most people don't think about this?

Those shots were fired for the group only, the aiming point was the small diamond in the center of the target

A possible variant might be related to breaking the sound barrier. A round ball is not the most ballistically effective design and encounters significant bow wave issues when breaking the barrier. Shooting velocities that break the sound barrier could happen at different points along the trajectory, depending on the velocity of the load. It could possibly affect POI. That being said, most of us probably can't out shoot the result. My .50 caliber flintlock shoots very accurately with loads ranging from 65 to 110 grains of 2FF. Seventy five grains of 2FF produces the tightest groups most consistently. The search for the "sweet spot" is half the fun.

Very true and it happens twice if you're shooting long range once at the muzzle and again when the projectile drops below sonic.

 

[Erwan]

kelljp[/USER]]Was reading an article about accuracy in a modern rifle and the ammo manufacturer was stating there ammo for accuracy had a slower velocity to improve accuracy. That being said I wondered had anyone tested this concept in black powder rifles. I would assume it would follow suit. Even though I have always tried to achieve the max velocity. Maybe that is why I am a ousy shot.

Did you hear something about a Gaussian curve?

 

[longcruise]

Did you hear something about a Gaussian curve?

View attachment 369711

Shucks, I've never heard of a gaussiajn curve. What's it tell us and what data goes into it?

 

[LME]

Did you hear something about a Gaussian curv

Shucks, I've never heard of a gaussiajn curve. What's it tell us and what data goes into it?

I bet you have heard of the bell curve? Same thing but your professor prefers the ,"Gaussian curve"!

 

[longcruise]

I bet you have heard of the bell curve? Same thing but your professor prefers the ,"Gaussian curve"!

Aha! Of course. I stll wonder what ml data would be input and what would it tell us?

 

[Erwan]

Aha! Of course. I stll wonder what ml data would be input and what would it tell us?

In this case, you can compare the relationship between velocity and accuracy using a Gauss curve. To begin with, and before choosing the most appropriate load according to calibre and base load, and therefore the bullet velocity, you must follow this curve. Initially, the velocity is not good and the dispersion is high. If you increase the load, and therefore the velocity, your dispersion cone will begin to decrease, it will decrease more and more until it reaches the highest point of the curve, and if you continue to increase the velocity, your accuracy will begin to decrease, and the higher the velocity, the more you will be on the wrong side of the curve: your dispersion cone will deteriorate more and more until it returns to the lowest point, as if you hadn't worked on your load and had stayed on the minimum basic load, which is most often 1 calibre for 1 grain, for example 45 grains for a .45 calibre, which happens to be the most common starting load before fine-tuning the load, and therefore the velocity/accuracy ratio, to find the load that suits your gun.
I don't know if I've made myself clear, as I often find it difficult to explain certain basic technical principles in your language.

Erwan.

 

[Stykbow]

I never thought about applying a bell curve to shooting, but it would work. I use those on occasion in my work. Back to the question of a lower velocity being more accurate in ML’s. Have you ever noticed how small most folks powder charge is on here? They say it’s more economical and it is, but it’s also generally very accurate for those guys. I get it, but it’s just not in me to shoot 45 or 50 grains of powder in a 50 cal ML.

 

[wiscoaster]

I bet you have heard of the bell curve? ....

Aha! Of course. I stll wonder what ml data would be input and what would it tell us?

A "bell curve" is a normal distribution of data points. In the case of ML load development, it would be a graph of the offsets of the impact points from the aim points versus loads used. It's a statistical measure of qualifying the significance of the results. It's got nothing to do with projectile trajectory. A broad curve means the impact results were distributed over a wide variation, while a steep sharp curve means the impact results were distributed over a narrow variation. Obviously, the narrow variation is a more desirable result. The "peak" of the curve is the mean (aka "average") of the entire group of measurements, and a "standard deviation" is taken from the width of the curve at a certain point, where the number of data points under the curve equals a defined mathematical formula ("sigma"), and which may be interpreted as a measure of the width of the distribution of those data points. Obviously, a smaller standard deviation is a more desirable result, and signifies greater consistency of points of impact. The peak of the curve would signify where the load with the most impacts within the standard deviation, and thus the best load for accuracy and consistency.

 

[Erwan]

Have you ever noticed how small most folks powder charge is on here? They say it’s more economical and it is, but it’s also generally very accurate for those guys. I get it, but it’s just not in me to shoot 45 or 50 grains of powder in a 50 cal ML

I understand exactly what you mean, but two or three things are still very different: target shooting, hunting, and last but not least, pleasure.

Today, I used 36 grains of French BP (PNF1) 3Fg with a Pennsylvania .45 (.445 balls and .013" patches) rifle at 50 meters just for target shooting. This is a very low load but extremely accurate and precise for this rifle, that permits today a group of 1.45x1.45" and 97/100 points (MLAIC rules). That way is just for the precision and too soft for pleasure and/or hunting, it all depends on what you expect from BP flintlock shooting and for what you do it...

 

[Doug Fay]

I wonder if passing through the speed of sound would affect accuracy? A lot of funny stuff happens at that point. Like if the muzzle velocity was just over the speed of sound. I think muzzleloaders can shoot that fast, but I'm not sure.

And I'll add shape and surface of the bullet - E.g., golf balls have all those dimples all over them to break up laminar flow so that trailing vortexes don't slow them down and make them go all over the place as much (if I recall correctly).

Hey - that gives me an idea: maybe I should put dimples all over my flintlock round balls I wonder if anybody has ever tried that. My guess is they have tried it, and it didn't work, which is why round balls are not dimpled. Oh, well, there goes another great idea :-/

 

[Erwan]

I wonder if passing through the speed of sound would affect accuracy? A lot of funny stuff happens at that point. Like if the muzzle velocity was just over the speed of sound. I think muzzleloaders can shoot that fast, but I'm not sure.

Not exactly, when I'm shooting at 100 meters with my Pedersoli Tryon and 500 grains bullets (target shooting) the speed is over 400 meters/second and the sound is at 340 m/s (~1115 Fps). Ok, those bullets are paper-patched, but they fly over the sound speed with any loss of precision. There isn't the real problem: Frequently the speed is around 600 m/s (also paper-patched bullets) for Black Powder Target Rifle Creedmoor Championships and the precision is at the "Rendez-vous" in long-range...

 

[longcruise]

I don't know if I've made myself clear, as I often find it difficult to explain certain basic technical principles in your language.

That was pretty clear. I doubt if I'll try it though!

it all depends on what you expect from BP flintlock shooting and for what you do it...

That's the key. What's it to be used for.

I know a few guys who shoot matches and vary the powder charge based on the range. 8 have several rifles that shoot accurately up and down the powder scale. So, a project I'm going to do when the weather warms up and the wind calms down. My thoughts are to zero at 50 yards with a mid range charge and then shoot various charges at 25 and 100 to find the ones that shoot to poa. If accuracy is good I'll give it a try in a match.

I know! Just hold over or under, right? That's what I've done for a long time but with aging eyes maybe this would improve scores by having POI match POA.

 

[Ed C.]

That was pretty clear. I doubt if I'll try it though!

That's the key. What's it to be used for.

I know a few guys who shoot matches and vary the powder charge based on the range. 8 have several rifles that shoot accurately up and down the powder scale. So, a project I'm going to do when the weather warms up and the wind calms down. My thoughts are to zero at 50 yards with a mid range charge and then shoot various charges at 25 and 100 to find the ones that shoot to poa. If accuracy is good I'll give it a try in a match.

I know! Just hold over or under, right? That's what I've done for a long time but with aging eyes maybe this would improve scores by having POI match POA.

The problem I have with holding over the target at 100 yards is that the target becomes hidden by the barrel so I go from using 60 grains at 50 yards to 75 grains at 100 yards and am able to use the same POA.