Any difference in point of impact when using different powders?

[Artificer]

If the velocity of the ball is higher, it will remain in the barrel for less time than it would if the velocity is lower.

That gives less time for the barrel to rise before the ball reaches the muzzle.

That will sometimes cause the shot to hit lower even though the velocity was higher.

The increase in recoil of the higher velocity shot and greater barrel rise that goes along with it may or may not over ride this "time in the barrel" difference so it is difficult to predict which will have the greatest effect.

One thing that can be predicted is, pistols are much more likely for this cause and effect to be noted than larger and heavier rifles.

The individuals

Hi Zonie,

I won't disagree that a higher velocity/higher energy ball will cause the barrel to rise more in human hands because of the higher recoil energy. This is counter balanced to a degree by less time in the barrel, as you wrote, though I also am unsure as to how much.

However, the places I first learned of higher velocity/energy rounds hitting lower on target were from using Ransom Rests bolted down on concrete pillars for pistols and especially in an extremely costly machine rests (also bolted down on concrete pillars) that held Service and Sniper Rifles for accuracy testing. Though the devices were bolted down, they did allow recoil energy to "bleed off" in different ways.

The rifle test "racks," or machine rests, had a strap that kept the barrel from rising. The recoil energy was absorbed/bled off by primarily an extremely heavy rest and also because the rest traveled on a slightly inclined precision guide rail system.

Where the higher velocity rounds hit lower on target were at distances where the projectile/s were still rising in their arcs of travel. This also happens with ML projectiles, even though the balls/projectiles are normally larger/heavier and at lower velocities.

Now, if the distance to the target w/either type of gun, is at the point where the projectile is falling below its highest point in the arc, then higher velocity rounds will hit higher on the target because they don't fall as quickly. This is why we describe higher velocity rounds as "flatter shooting" throughout the length of their arc, but especially after they go past their highest point in their arc of travel.

So, depending at what point the target is placed in a projectile's flight path, the higher velocity projectile will hit lower or higher on the target. This is true for both ML and modern guns.

Gus

 

[Artificer]

P.S. Dang it, cut my post off too early.

OK, since a lot of our target shooting in ML'ing is at ranges where the projectile is still traveling upwards in the arc of it's flight path, then it normally will be more common to see the higher velocity projectiles hitting lower on the target.

Gus

 

[Kansas Jake]

Quote
"Now, if the distance to the target w/either type of gun, is at the point where the projectile is falling below its highest point in the arc, then higher velocity rounds will hit higher on the target because they don't fall as quickly. This is why we describe higher velocity rounds as "flatter shooting" throughout the length of their arc, but especially after they go past their highest point in their arc of travel."

Gus,

You state the "higher velocity rounds will hit higher on the target because they don't fall as quickly." If I remember my high school physics class correctly, I think they fall just as quickly, but just have less time to fall. :grin:

Jake

 

[Gene L]

A faster powder/velocity will cause the impact to be lower because the dwell time in the barrel is shorter and the barrel has less time to rise in recoil. Or, to say it the other way, a slow bullet stays in the barrel longer and is acted on by recoil for a longer time period.

I know, this sounds counter-intuitive, but it's the way it is and with a longer barrel, the difference will be even greater.

Huh? :hmm:

Look it up.

 

[Artificer]

Quote
"Now, if the distance to the target w/either type of gun, is at the point where the projectile is falling below its highest point in the arc, then higher velocity rounds will hit higher on the target because they don't fall as quickly. This is why we describe higher velocity rounds as "flatter shooting" throughout the length of their arc, but especially after they go past their highest point in their arc of travel."

Gus,

You state the "higher velocity rounds will hit higher on the target because they don't fall as quickly." If I remember my high school physics class correctly, I think they fall just as quickly, but just have less time to fall. :grin:

Jake

Hi Jake,

Yes, you are talking about the effects of gravity being equal on the bullet/projectile, no matter where it is at after it leaves the barrel.

But, yes, I could have written that better. Let's just say with the higher velocity balls/projectiles that after they travel beyond the peak of their arc, they still have more forward inertia than lower velocity balls/projectiles, so the forward inertia resists gravity more and the balls/projectiles go further before hitting the ground.

Gus

 

[Rifleman1776]

A faster powder/velocity will cause the impact to be lower because the dwell time in the barrel is shorter and the barrel has less time to rise in recoil. Or, to say it the other way, a slow bullet stays in the barrel longer and is acted on by recoil for a longer time period.

I know, this sounds counter-intuitive, but it's the way it is and with a longer barrel, the difference will be even greater.

Huh? :hmm:

Look it up.

I do. Every time I go to the range I read targets. :shocked2: Higher charges always result in higher poi.

 

[Artificer]

Are you talking about all ranges say 25, 50, 75, 100 and more yards; or just at the longer ranges?

What caliber/s are you shooting?

Also, is that from bench, offhand or other shooting positions?

How much more powder increase does it take to see the difference?

I am not arguing or trying to pin you down, just would like to know more specifics.

Gus

 

[Rifleman1776]

Are you talking about all ranges say 25, 50, 75, 100 and more yards; or just at the longer ranges?

What caliber/s are you shooting?

Also, is that from bench, offhand or other shooting positions?

How much more powder increase does it take to see the difference?

I am not arguing or trying to pin you down, just would like to know more specifics.

Gus

Yes, the popular ranges.
Mostly .45 prb but also observing/scoring other rifle calibers from .32 to .72.
With my .45 a five grain increase will raise impact one to two inches at 100 yards. Another five (total ten) doesn't seem to influence that much more at 100 yards.

 

[Rifleman1776]

This thread reminds me of a theory a (former) friend had regarding bent barrels.
He was a life long muzzle loading shooter, rifle builder, etc. He was also 34 years Special Ops with sniper experience and was on the Army rifle team. In addition he was a trained engineer. Lots of skills and impressive resume.
But, his bent barrel theory was/is, IMHO, pure nonsense.
He postulated that if a barrel (ml or modern) is not perfectly straight the projectile will continue on a curved path after leaving the muzzle. He could quote mind numbing mathematical "proof" that this really happened.
I, and many others, simply do not accept his theory. I believe, failing other influences, like wind and gravity, the projectile will travel in a straight line after leaving the barrel.
What say the jury?

 

[azmntman]

I can see his point but I have no opinion. If my barrel gets bent I get another barrel. I like straight

 

[hanshi]

I agree with Zonie on his conclusions; at least that has been my experience with both muzzleloaders AND modern rifles. And I also know that a projectile does indeed go in a straight line upon exiting the muzzle. I've also found that revolver/pistol bullets do the opposite by striking lower as velocity increases.

 

[Java77]

I went to the range today to try Goex. It was really windy and cold so didn’t stay long.

I shot at 25 yards. I swabbed the bore with bore cleaner and a dry patch between each shot. The picture of the target is a group of 5 shots.

I found Goex shot low and to the left similar to the Swiss. However it seemed to group about an inch higher and tighter.

Maybe it’s just my gun being a 40 cal but the Goex seems to foul more than the Swiss. Even though I swabbed between each shot, it seemed to take more effort after each shot.

I have been using 50 grains as recommended by the builder.

 

[Artificer]

Are you talking about all ranges say 25, 50, 75, 100 and more yards; or just at the longer ranges?

What caliber/s are you shooting?

Also, is that from bench, offhand or other shooting positions?

How much more powder increase does it take to see the difference?

I am not arguing or trying to pin you down, just would like to know more specifics.

Gus

Yes, the popular ranges.
Mostly .45 prb but also observing/scoring other rifle calibers from .32 to .72.
With my .45 a five grain increase will raise impact one to two inches at 100 yards. Another five (total ten) doesn't seem to influence that much more at 100 yards.

Thank you for the information. I wonder how five grains raises the POI significantly, but another five grains does not do that much more?

The bent barrel theory is easily disproven by empirical evidence.

On the other hand, empirical evidence from the test racks I mentioned did show with higher velocity that the bullets hit lower on target while still rising and hit higher on target when they were beyond the peak of their arc in flight. That was without human holding or other errors.

Now, of course the human element can cause the results to change for a number of reasons.

Gus

 

[Gene L]

First of all, a powder that gives higher velocity (like Swiss is reported to be) will often cause the Point of Impact (POI) of groups to be lower on target than a powder that gives slower velocity (like DuPont/Goex). Now that seems to be contradictory that a higher velocity powder will cause lower POI, so allow me to try to explain.

The ball does not follow the path of the sights. The ball is rising as it leaves the muzzle of the barrel at shorter range, because the barrel is pointing higher than the line of the sights. (The bullet travels in a arc and will rise above the line of sight along its path and lower than the target further along.) Gravity is also acting on the ball during the entire time of its flight path. So when a ball travels faster, it doesn't have as much time to rise and thus hits lower on target.

Different powders can/will definitely affect group size, even when the same volume of powder is used, and can/will also affect the size of the groups.

However, much has been written on how each person places his cheek on the stock and thus how his eyes see the sights. Even the same person who uses the exact same load in his rifle, will see a group shift from the Point of Aim to the Point of Impact when he moves his cheek to a different part of the stock to aim.

Also, because we all have different vision with different variances of visual acuity and problems, points of impact can easily be different between two people using the exact same load and rifle.

I agree with others that one must take away as much human error as possible when sighting in, to determine if the errors in POI and/or of group size, are from the shooter or the gun.

Gus

Exactly. Since the bullet must rise from the line of sight, the path is a minor parabola. If you placed the barrel exactly level, the bullet would hit the ground at a very short distance away. Likewise, if you put the barrel exactly level and dropped a ball at the exact time the bullet left the barrel, both would hit the ground at the same time.

 

[George]

On the other hand, empirical evidence from the test racks I mentioned did show with higher velocity that the bullets hit lower on target while still rising and hit higher on target when they were beyond the peak of their arc in flight.

I'm finding it a bit difficult to follow your description of the effect on the trajectory of an increase in velocity. Am I right that you are talking about a situation where the target is not at the far zero, the range at which the gun is "sighted in"? Increased velocity lowers the Mid-Range Trajectory and raises the Point of Impact at the sighted range...'shoots flatter'... so if I'm understanding you correctly, that would match what you describe.

Spence

 

[Gene L]

At zero ranges, the stronger charges will zero lower. But at longer ranges, the slower bullets will be acted on by gravity for a longer period of time and will definitely shoot lower.

 

[George]

At zero ranges, the stronger charges will zero lower.

Not quite sure how you are using the term 'zero'. If you have the gun sighted to hit the X at 100 yards and you increase the velocity by increasing the charge, the ball will hit higher. The increased velocity means time to target is less so drop is less, ball will strike higher with the same sight picture.

Spence

 

[Artificer]

On the other hand, empirical evidence from the test racks I mentioned did show with higher velocity that the bullets hit lower on target while still rising and hit higher on target when they were beyond the peak of their arc in flight.

I'm finding it a bit difficult to follow your description of the effect on the trajectory of an increase in velocity. Am I right that you are talking about a situation where the target is not at the far zero, the range at which the gun is "sighted in"? Increased velocity lowers the Mid-Range Trajectory and raises the Point of Impact at the sighted range...'shoots flatter'... so if I'm understanding you correctly, that would match what you describe.

Spence

Yes, I think we are on the same page.

Gus

 

[Rifleman1776]

I wonder how five grains raises the POI significantly, but another five grains does not do that much more?

Me too wonders about that. But, it is a strange game.

 

[Rifleman1776]

If you have the gun sighted to hit the X at 100 yards and you increase the velocity by increasing the charge, the ball will hit higher. The increased velocity means time to target is less so drop is less, ball will strike higher with the same sight picture.

Exactly. Higher velocity means flatter trajectory and less time for gravity to act on the ball. Voila = higher poi. Methinks it is such an obvious and simple concept lots of discussion and mathematics are unnecessary.
Actually, all this discussion has produced some widely varied opinions. I hope the line has not been crossed and we still like and respect others. Not often I say to a couple of the guys on this thread they are wrong. Peace, Bros. :v