Velocity affect accuracy ?

[cjgregory]

Can you post a picture showing how you rest your rifle for load development? How a rifle rests in bags on a bench greatly influences point of impact. If you develop an accuracy load off the bench that changes (barrel harmonics) when the rifle is fired offhand, then the result is a waste of time, powder and lead (in my humble opinion).

My rifles are used for hunting and informal shooting, not competition. I'm all about accuracy and could care less about velocity. The load must be repeatable in order to learn trajectory. The point of impact off the bench must match POI from the offhand position. There enough variables in developing a patched ball accuracy load, beginning at the bench.

Here are a couple of pics. With the trigger guard up to the support, it’s almost the balance point. The barrel touches nothing.
Just remember that in the field, if you have a tree to rest against, make sure you rest it back close to the lock. Never rest the barrel on anything. Off hand is always the best. Practice.
A long rifle is the finest off hand rifle ever made.
The rifle is a 42” .36 caliber rifle my buddy made for me.
Presently he’s is building me a Dickert, Lancaster with a swamped 44” barrel in .54 caliber and a chambers golden age flintlock.
This will be my big game hunting rifle.

 

[longcruise]

I stated cartridges in the post.

I thought that was it.

 

[Coinneach]

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 :-/

It kinda works, use a slab of concrete and a large enough retaining ring (to hold enough round balls in place) sweep and vacuum the area where the retaining ring is placed, wearing a thin rubber glove roll a small handful of the balls around in a figure 8 motion until they looked "dimpled" enough. Then swish them around in some water to de-dust them and allow to dry.

Give it a try if you're interested.

 

[ChuckJonesWagon]

It kinda works, use a slab of concrete and a large enough retaining ring (to hold enough round balls in place) sweep and vacuum the area where the retaining ring is placed, wearing a thin rubber glove roll a small handful of the balls around in a figure 8 motion until they looked "dimpled" enough. Then swish them around in some water to de-dust them and allow to dry.

Give it a try if you're interested.

That's interesting......but (always a "but") for the distances a flintlock rifle or pistol is shot, does it really make a significant difference in velocity or accuracy?

 

[tenngun]

That's interesting......but (always a "but") for the distances a flintlock rifle or pistol is shot, does it really make a significant difference in velocity or accuracy?

I’ve noted smooth bore shooters often have great groups with extra large charges, I’ve not tried it myself
The theory is 1)large charges blow past a bare ball creating a plasma patch or 2) the high velocity gets the ball to the target before other factors move the ball off target
Even a wind too small for you to notice can move a ball, and higher velocity means less time in flight to deviated
Angels with weak bladders are always there to miss up out shot

 

[Absoroka]

Based on countless hours with a chronograph, I have found that the load with the smallest deviation in velocity shot to shot also produces the tightest groups, all other elements being consistent. That also makes sense from a logical standpoint. During my experimentation which was done some years ago, I used GOEX and Elephant. The most consistent results from a deviation standpoint were produced with Elephant, but more powder was required to achieve that result since Elephant developed less velocity for an equal charge by volume. I also found it interesting that the most accurate (read tightest groups) loads with both powders produced the same velocity with averages about 35-40 feet per second apart.

 

[Coinneach]

That's interesting......but (always a "but") for the distances a flintlock rifle or pistol is shot, does it really make a significant difference in velocity or accuracy?

I cant say that it does, there again I didnt conduct any meaningful trials or testing to speak of.
My "giving it a try" was more of a curiosity than striving for comparisons, although as I recall there wasnt much difference in groupings. BTW I didnt use a Chronograph.

 

[Doug Fay]

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...

If the bullet stays supersonic all or even most of the way to the target, I can see that there probably won't be a problem.

What I was wondering is, if the bullet leaves the muzzle above the speed of sound, but then falls below the speed of sound significantly before hitting the target, whether the trans-sonic part of its flight would throw it off. I got that idea from watching "The Right Stuff" where Steve Yeager has trouble controlling the Bell X1 while going from under to over the speed of sound (and assuming the same sort of turbulence would occur when going from over to under the speed of sound)

 

[Rock Home Isle]

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.

Without going through and reading every post, here are my thoughts, and understanding. Chances are someone has already posted this, and I’m probably just going to repeat here…

As you increase the charge, you increase the velocity of the projectile. Very simple.

But as you increase the charge you also impart an acceleration impulse into the projectile, where the rear of the projectile will accelerate faster than the front of the projectile. This causes the projectile to squeeze front to back, and expand into the rifling of the bore.

As you increase the charge, velocity increases, and the engagement with the rifling increases. The more that the projectile engages the rifling, the better the accuracy. However, there is a point at which acceleration, and velocity are so high that the projectile jumps the rifling, and accuracy completely fails. The charge that gets you closest to the point of the projectile jumping the rifling, is usually the most accurate load.

And to add insult to injury, the system will experience peaks and valleys in accuracy as charges increase and higher velocities are obtained.