Any difference in point of impact when using different powders?

[Kansas Jake]

Just a thought. Maybe that last 5 grains got to the point where additional powder was not fully consumed in the barrel and didn't add much to velocity. Another possibility is the additional velocity from the last 5 grains of powder was such that it didn't move the trajectory curve any more on the target. Does that make sense to anyone?

 

[George]

Just a thought. Maybe that last 5 grains got to the point where additional powder was not fully consumed in the barrel and didn't add much to velocity.

I don't believe in the idea that there's only a certain amount of powder which can be burned in a given length of barrel and that powder above amount that is blown out.

Another possibility is the additional velocity from the last 5 grains of powder was such that it didn't move the trajectory curve any more on the target. Does that make sense to anyone?

It's correct that 5 grains will move the POI only a very small amount, because the increase in pressure/velocity from 5 grains is very small.

Spence

 

[nhmoose]

Not to Spence, but everyone.

After competing in black powder line shoots I can say any change in loading components or procedures WILL make a difference in impact of the shot, no doubt about it.

Sight for what you use, big deal making a correction. IMHO

 

[Col. Batguano]

Let me throw in a few other variables;

1.) Weather. The test target may have been shot in different atmospheric conditions than when you shot it. Colder, warmer, less humid, more humid, wind.

2. ) Load. Powder type, Lube, ball diameter, patch thickness, charge compression. picking, not picking the vent hole, swabbing between shots

3.) Technique. In addition to trigger technique, the test target shooter may have rested the fore end differently than you did, Further toward the muzzle, closer to the breech. Guns will often shoot to different points of aim in different positions, especially when you are chasing X's. If you think about it, standing position requires supporting hand to be very close to the breech regarding hand placement. Off the bench it's further away which can influence barrel harmonics, bend, and a whole host of related issues.

 

[Artificer]

Just a thought. Maybe that last 5 grains got to the point where additional powder was not fully consumed in the barrel and didn't add much to velocity.

I don't believe in the idea that there's only a certain amount of powder which can be burned in a given length of barrel and that powder above amount that is blown out.

Absolutely!! :thumbsup:

That idea is actually a very old myth that was disproven by the Royal Society of London in the very early 1750's. They proved most of the powder was burned in the first inch of the barrel from the breech and all of it was consumed within two to three inches, depending on bore size and powder charge.

Yet this myth continues with us today and for some reason, just refuses to die.

I cannot document this, but I think the myth got started in the 18th century (or even earlier) because they were trying to explain why longer barrels shot with a flatter trajectory than short barrels, in the same caliber and with the same powder charge. What they did not know was the patched ball increased in velocity inside the longer barrels more, even though all the powder was burnt up very near the breech.

Gus

 

[Holdin 6]

Of course it would continue in a curve. That's how you shoot around trees, and hit the deer behind it :youcrazy: .........

 

[Holdin 6]

Regardless of time, speed, or distance, Gravity is a Constant. Physics 101.

 

[Rifleman1776]

standing position requires supporting hand to be very close to the breech regarding hand placement. Off the bench it's further away which can influence barrel harmonics, bend, and a whole host of related issues.

The general rule I was taught and found best is, for offhand rifles from the bench, rest at the same point as you would be holding for stand up. For rifles designed for bench only (heavy, long barrels, etc.) you rest where it works best and stay with that. On the ranges you will see a lot of different methods used.

 

[Rifleman1776]

Of course it would continue in a curve. That's how you shoot around trees, and hit the deer behind it :youcrazy: .........

:grin: :v

 

[Rifleman1776]

Regardless of time, speed, or distance, Gravity is a Constant. Physics 101.

'splain please: How does less time for gravity to have a pull on the ball lower the poi?

 

[Twisted_1in66]

The ball actually continues to drop at the same rate from the point of fire as the slower ball, meaning that with the same point of aim it takes the same amount of time to drop to the ground as the slower ball does. But it travels farther in that same amount of time. Because they both get to the same distance (point of impact) at different times, they have dropped different amounts at the same distance.

Time to target is the key here. The faster ball reaches the point of impact before the slower ball does. The faster ball doesn't drop as much as the slower ball because not enough time has elapsed to allow it to drop as much at that distance.

Twisted_1in66 :thumbsup:
Dan

 

[George]

'splain please: How does less time for gravity to have a pull on the ball lower the poi?

That depends on where the POI is in relation to the distance the gun is sighted for. If the gun is sighted for 100 yards, then at 100 yards a faster ball will hit the target higher, not lower, because, overall, there is less time for gravity to pull it lower.

That's not necessarily the case when the target is at a different distance than the one the gun is sighted for.

Every ball travels a looping path to the distance it's sighted for. First it climbs up and then it falls down, and that means there is a point at which it is at its highest. That point is called the Mid-Range Trajectory (MRT), and is approximately half way to the sighted distance.

In your case, if the target/POI is between the muzzle and the MRT, then the faster ball won't have time to climb so much, so the POI will be lower. So will the MRT.

Spence

 

[Rifleman1776]

'splain please: How does less time for gravity to have a pull on the ball lower the poi?

That depends on where the POI is in relation to the distance the gun is sighted for. If the gun is sighted for 100 yards, then at 100 yards a faster ball will hit the target higher, not lower, because, overall, there is less time for gravity to pull it lower.

That's not necessarily the case when the target is at a different distance than the one the gun is sighted for.

Every ball travels a looping path to the distance it's sighted for. First it climbs up and then it falls down, and that means there is a point at which it is at its highest. That point is called the Mid-Range Trajectory (MRT), and is approximately half way to the sighted distance.

In your case, if the target/POI is between the muzzle and the MRT, then the faster ball won't have time to climb so much, so the POI will be lower. So will the MRT.

Spence

OK, we agree on the first part. :applause:
But that last part, not at all. The "looping" trajectory will have the ball higher than the desired poi at 100 yards. Meaning, at 50 yards it will hit higher, never lower.

 

[George]

The "looping" trajectory will have the ball higher than the desired poi at 100 yards.

Not true. If the rifle is sighted in for 100 yards, it will hit exactly on the X at that range with that velocity. Shoot the same ball faster, it will hit higher. Shoot it slower, it will hit lower.

Meaning, at 50 yards it will hit higher, never lower.

It doesn't work that way. Faster balls travel a flatter path, the highest point of the "loop" is lower.

Spence

 

[azmntman]

Range time to see for sure :hmm:

 

[George]

Range time to see for sure :hmm:

All of this was worked out decades ago by people much more qualified than I. Any errors in my description of it are my errors, not that in the base of solid knowledge built up over many, many years. I won't be going to the range, been there and done that, but if anyone wants to test my description at the range I'll look forward to the report. :grin:

Spence

 

[Twisted_1in66]

The "looping" trajectory will have the ball higher than the desired poi at 100 yards.

Not true. If the rifle is sighted in for 100 yards, it will hit exactly on the X at that range with that velocity. Shoot the same ball faster, it will hit higher. Shoot it slower, it will hit lower.

Meaning, at 50 yards it will hit higher, never lower.

It doesn't work that way. Faster balls travel a flatter path, the highest point of the "loop" is lower.

Spence

If you have sighted in your rifle for 100 yards with the velocity you are consistently getting, then yes it will be shoot high by usually a couple of inches or more at 50 yards. That is because you have to shoot your round ball (or bullet) in an arch to hit the point of aim at 100 yards. Typically that means you will shoot a little low at 25 yards, high at 50-yards, back down a bit at 75 yards and spot on at 100 yards. That "spot on" is actually called "point blank" because the point of impact and the point of aim are exactly the same.

Here's a chart from my ballistics program. The settings for this example are listed on the left. It's for a .490 lead ball with an initial muzzle velocity of 1900-fps fired under ideal conditions. The sight height is off slightly as my sights measure 3/16" which is 0.1875, and the program rounded that up to 0.2 but that makes a negligible difference.

I adjusted the visible part of the chart so you can see from 50-yards out to 120-yds. Notice the height of the ball at 50-yards to get to 0.0 at 100-yards traveling at 1900-fps. The ball has to travel in an arch to reach that point of aim at 100-yds.

Now here's another ballistics chart with initial muzzle velocity at 2200-fps.

Take a look at the 50-yard spot again. Notice how much lower it travels at that higher velocity to reach the same POI at 100-yards (2.4" high vs 3.1" high)? That's quite a bit less. That's because it gets there faster.

The 2200-fps shot gets there .029 of a second faster than the 1900-fps shot and that's the key. You don't have to fire as high of an arch to get to your sight-in point of aim because the ball is getting there faster and doesn't have as much time to drop. It still drops at the same rate, but it travels farther in less time and just doesn't have as much time to drop as the slower ball does before it hits the target.

This is what people often refer to as a "flatter trajectory. It's really not a good phrase for what happens, but that's what's in common use. The physical amount of drop is time-sensitive. The more time the ball is in the air, the more it's going to drop. By speeding the ball up, there is less time in the air and thus less drop at the same distance (in this case 100-yards).

Hope that helps...

Twisted_1in66 :thumbsup:
Dan

 

[smo]

Thanks for the info Twisted :thumbsup:

Here is the definition of point blank for everyone ...

Point-blank range is any distance over which the trajectory of a given projectile fired from a given weapon remains sufficiently flat that one can strike a target by firing at it directly. Point-blank range will vary by a weapon's external ballistics characteristics and target chosen. A weapon with a flatter trajectory will permit a longer maximum point-blank range for a given target size, while a larger target will allow a longer point-blank range for a given weapon.


I have always been told that the projectile crosses the intended line of sight twice....once at close range then again at the poi.

This being due to the arch in its trajectory .
In your examples above even the 1900 FPS load appears it would be point blank on a deer size target out to 120 yards.

Unless I’m totally confused....again.

Twisted, would you mind running your program for a .530 ball at 1400 FPS. Sighted at 100 yards. Thanks

I would think it would be way high at 50 and low at 25 as well... :idunno:

 

[George]

The definition I've always used for 'point blank range' is related to the MRT, mid-range trajectory, so it's a definite distance. The bullet will continue to fall after it passes the distance for which the gun is sighted in. When it has fallen as far below the line of sight as it was above it at the MRT, that's the point blank range. For example, a .535" ball at 1540 fps sighted in at 75 yards will have a MRT of 1.2" at 45 yards. When it has fallen 1.2 inches below the line of sight it will be at 86 yards, which is the point blank range for that ball at that velocity. Out to that distance the ball won't be more than 1.2" above or below the line of sight.

Spence

 

[Rifleman1776]

The "looping" trajectory will have the ball higher than the desired poi at 100 yards.

This thread is starting to sound a lot like the old "who's on first?" comedy routine. :rotf:

Yes :redface: I did have a brain blip when I typed that. Meant to say "at 50" yards. I know better. Am I still in trouble. :shocked2: :wink: :v