Any difference in point of impact when using different powders?

[Java77]

I took my rifle out for a extended session today to practice shooting a flintlock. I found that shooting off of a rest, the shots were impacting low and left.

The builder sent a test target with the rifle and was dead on. He did say to use Goex fffg but I was only able to purchase Swiss fffg.

So would different powders cause a shift in groups with all other factors being the same?

Thanks.

Bill

 

[Canute Rex]

I could see the change in powder changing the height of impact due to velocity change. The left/right is something else.

That is, if the shots were grouping well.

I have never used Swiss, but I have always heard and read that it is actually more bang for the same grain weight. You'd think that would raise the POI. Did you use the same powder charge, patch and ball combination? A slicker lube or looser patch/ball combo could lower velocity and drop POI.

You write that you wanted to "practice shooting a flintlock", implying that you aren't used to it. That could point to your follow-through, that is, your moment of (ideally) motionlessness after you pull the trigger. A little flinch goes a long way to pulling the POI horizontally.

Try putting a little chip of wood in place of the flint and dry firing the unloaded rifle. Set it on the rest, aim dead center, and dry fire. Then look to see where the rifle is aimed.

Just don't mess with the sights until you eliminate all the other factors.

Good luck!

 

[Nomadexpedition]

That is a great tip thanks for the dry firing tip.

 

[Java77]

I could see the change in powder changing the height of impact due to velocity change. The left/right is something else.

That is, if the shots were grouping well.

I have never used Swiss, but I have always heard and read that it is actually more bang for the same grain weight. You'd think that would raise the POI. Did you use the same powder charge, patch and ball combination? A slicker lube or looser patch/ball combo could lower velocity and drop POI.

You write that you wanted to "practice shooting a flintlock", implying that you aren't used to it. That could point to your follow-through, that is, your moment of (ideally) motionlessness after you pull the trigger. A little flinch goes a long way to pulling the POI horizontally.

Try putting a little chip of wood in place of the flint and dry firing the unloaded rifle. Set it on the rest, aim dead center, and dry fire. Then look to see where the rifle is aimed.

Just don't mess with the sights until you eliminate all the other factors.

I’m using the same patch (Ox-yoke patch .010), same charrge (50 grn 3f) and same size ball.

This is my first flintlock. I don’t think I’m flinching but may be. I had the RO shoot a vid so I can see what I’m doing.

https://youtu.be/zgwz6Jcu3b4

Thanks for the tips!

 

[Walks with fire]

I have never found Swiss to be more accurate than Goex powder and while it may have more velocity per volume charge I have never cared for it. It could be the climate here in Northwest Pa but Swiss leaves a much drier fouling in the bore than Goex does as well. I tinkered with Swiss enough that I found Goex more to my liking. I also tinkered with Goex 3f enough to know that some barrels love it and some not so much. I let the barrel tell me which Goex granulation it prefers.

Goex 2f in a .50/.54 with a tight patch/ball with hunting loads is plenty good in velocity and accuracy. These are flinters.

 

[Grenadier1758]

The difference in the group is most likely due to the difference in hold between two people. Its also a different set of eyes that are aligning the rifle to the target. You may be setting the rifle on the rest in a different spot than the builder.

The first part of learning your rifle is establishing the group and getting that as small as possible. Then it is time to adjust the sights on the rifle.

Yes, there can be differences in powder performance that show up a movement of a group. Most of us (well me) can't tell the difference, but some people can.

 

[timothy prouty]

WELL looking at the video it look like you are wobbling which could throw your shot off

 

[Billnpatti]

I did not see any sign of a flinch in your video. I though you were holding pretty steady for an off hand shot. I couldn't tell from the video if there was much wind. Of course, wind could cause your shots to move horizontally. A difference in powder will cause vertical changes in your POI due to any changes in the MV. Before changing your sights, shoot a few groups from a bench rest in a low wind condition. This will tell you whether you need to make any changes in your sights and how to adjust your sights to get your POI where you want it.

 

[Rifleman1776]

So would different powders cause a shift in groups with all other factors being the same?

Answer: Yes. Different makes, even batches of the same brands, can/will affect groups and poi. Some of the more obsessive 'X' hunters will buy a large quantity of the same powder to help assure consistent performance.
For most of us, that kind of variance is not a concern. Although, as others have stated, Swiss is a bit 'hotter' than Goex and others. It will probably raise your poi and may open your group. You may have to reduce your charge a bit to get back to similar performance with Goex.
Personally, my jury is still out regarding Swiss. I have a lot on hand but illness has kept me away from the range for about two years. Come green up I'll be back and will then get acquainted with it's vagaries.

 

[Java77]

Ok thank you all for the tips and suggestions. I’m good ng to try and get some Goex to test.

 

[mooman76]

Some real intense bench shooters even buy their powder in large lots because different lots can cause minor differences. Your issue is probably mostly the way you shoot. Everyone shoot different and everyone views the sights and look through them different also.

 

[Canute Rex]

Another thing to consider: Does your new rifle have a harder trigger pull than your previous one?

I have seen an effect where a stiff trigger can drop the POI. You end up taking a little of the weight of the rifle on the trigger itself and when it releases the rifle "falls off" the trigger, dropping the muzzle.

The remedy is taking a tighter grip on the wrist so your forefinger is pulling against the rest of your hand instead of the weight of the rifle.

 

[B.Habermehl]

Percription glasses can definitely change poi from one shooter to another by a good six inches some times. When I rough in sights for a customer on a rifle I built I wear my contacts. If I wear my glasses there is a good bit of horizontal shift in poi. BJH

 

[Java77]

Another thing to consider: Does your new rifle have a harder trigger pull than your previous one?

I have seen an effect where a stiff trigger can drop the POI. You end up taking a little of the weight of the rifle on the trigger itself and when it releases the rifle "falls off" the trigger, dropping the muzzle.

The remedy is taking a tighter grip on the wrist so your forefinger is pulling against the rest of your hand instead of the weight of the rifle.

This is my first flintlock and it has a double set trigger. I think I’ll run some tests using Goex. I just found a store that had it and bought 2 cans.

 

[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.

 

[azmntman]

This is my first flintlock and it has a double set trigger. I think I’ll run some tests using Goex. I just found a store that had it and bought 2 cans.

In California? Didnt Ma tell ya to stay away from that neighborhood :slap: :nono:

 

[Artificer]

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

 

[Zonie]

I suppose it doesn't matter too much but I disagree with your conclusion when you said, "...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."

The center of the barrel is pointed above the point of aim as you say.

The instant the ball leaves the muzzle it begins to fall below the center of the barrel line.

At lower velocities, because it takes more time to reach the target the ball will fall further below the center of the barrel line so, the slower it is traveling the further it will drop.
If the velocity is too low, the ball will drop well below the point of aim.

At higher velocities, the ball has less time to fall before it reaches the target so it will hit higher on the target.

Both of these statements assume the barrel doesn't move while the ball is accelerating towards the muzzle.

In real life, the barrel (and gun) begins to move rearward towards the shooters shoulder or hand (in the case of a pistol).

Because the barrel on most guns is above the resistance of the shoulder or hand it causes the muzzle of the gun to rise when the gun fires.


Higher velocities cause a greater rise of the barrel than lower velocities do because the rearward force is greater.

Now, for the real reason higher velocities can cause the shot to hit lower on the target:

With the barrel held exactly on target, the instant the gun fires the barrel starts to rise.

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

 

[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:

 

[Rifleman1776]

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.

That I can agree with. But, from my experience, whether offhand or rest with my rifle, larger charges result in higher poi.