Vertical stringing

[user 49399]

What is the most common cause of vertical stringing? I occasionally get this with a Thompson Center Hawken. But not always. This is the only gun I have that does this. Horizontal is right on the money.

 

[Flint62Smoothie]

The load ...

The projectile is exiting the bore while the barrel is moving the most through its harmonic vibrations, those sooooo miniscule you can't detect them. A barrel vibrates in a sinusoidal (sine) wave shape when fired, i.e., think of a small wave moving across a body of water.

The shot is most consistent when 'timed' to fire at the top or bottom of the wave. In BP, we affect this timing by changing the load. Look at the picture attached of an example of the groups when test fired from 50 to 75 grains. To be fair ... shoot just 1-shot of each powder charge at each dot, then go around again for a 3-shot group. This method 'normalizes the data' by allowing for variances in hold, bore fouling, sight picture and/or shooter technique and is a superior method than just shooting 3-shots at 50, then another 3 at 55 and moving up in charge weight that way.

The most accurate groupings here were 55 and 75 grains, but I continued development up to 100-grains for this one. This flintlock was a smoothbore, so don't worry about 'where' the group is in relation to the black dot ... as once done ... I bend my smoothie barrels to match it once I settle on a load. Clearly that ordeal is totally avoided with rifles, LOL!

 

[dave951]

There are several things that can cause vertical stringing- barrel harmonics, barrel bedding, powder charge, type/brand of powder, cap brand, lighting conditions, sights on the gun, and how you hold the gun. Also up for the culprit, wind, fouling and fouling mitigation, bullet weight.

We'll look at powder and sights first-

Yes, brand of powder and how you dispense it really does matter. I can change the charge level just 2g on my percussion Sharps and move the group 2in vertical. Weigh your charges and use a quality powder like Swiss or Old E to eliminate this variable. Regular Goex, Reenactor Goex or standard Schuetzen may be at fault, but I'd say how you measure it may be at fault.

Sights- buckhorn and bead are not the best sights for accuracy. When the front bead covers 8+moa, there is no way in the world you're going to be accurate and add in the buckhorn and buh bye accuracy. If you have post and notch, glare off the top of the front post will absolutely cause vertical strings. To eliminate this variable, try some Sight Black first. If that works, then invest in a RayVinn smoker to blacken the sights with carbon soot.

 

[dave951]

Next up-

Barrel harmonics- where you rest the front of the barrel will cause vertical stringing. It's especially pronounced on longer barrels. When benching the gun, do NOT rest the front on a sand bag. Put the barrel in your hand where you would normally offhand, use a reasonable firm hold, then rest the back of that hand on the sandbag. That will help to dampen a harmonic effect.

Barrel bedding- the inletting on the stock can affect the group depending on barrel temperature. That's why "longrifles" use an elongated hole where the barrel pins go. The barrel and wood expand at differing rates and if the barrel is not free to move lengthwise, it can start to "bend" in one direction causing a vertical string. To eliminate this variable you first have to control the powder charge variable and then fire groups very slowly allowing the barrel to cool between shots.

 

[Flint62Smoothie]

Good input from others too! Definitely check your barrel pins or wedge, but otherwise the hold and load are tha easiest to confirm.

For lighting conditions, that's usually only prevalent from one day to the next, unless you had a rare day where bright one minute and very cloudy the next minute. The old shooter's rule of "Light's up - Sights up" applies. Let's pretend you were shooting at a 4" black bullseye on a white paper background, holding at a 6 o'clock or 'lollipop' aiming point at the bottom edge of the bullseye (the best aiming spot for most accurate/consistent shooting when firing for groups or load development). Clearly for hunting or target shooting you may want to hold 'dead on'.

On really bright days your eyess can detect more 'white space' between the bullsyeye and your front sight, so you tend to hold away, off, or lower than the bullseye, so you actually need to hold higher on such bright days, sometimes even burying the blade up into the black.

 

[dave951]

For lighting conditions, that's usually only prevalent from 1 day to the next, unless you had a rare day where bright one minute and cludy the next. The old shooter's rule of "Light's up - Sights up" applies. Let's pretend you were shooting at a 4" black bullseye on a white paper background, holding at a 6 o'clock or 'lollipop' aiming point at the bottom of the bullseye (the best aim for most accurate/consistent shooting when firing for groups or load development).

On really bright days your eyess can detect more 'white space' between the bullsyeye and your front sight, so you tend to hold away, off or lower than the bullseye, but you'd need to hold higher on such bright days, sometimes even burying the blade up into the black.

That depends on the geometry of the front blade. If it has a radius on the back, good luck unless it's blacked. That is a huge source of glare and causes the target to appear to be floating over the post. Center hold can eliminate this if the target is a different color than black.

For load development, I disagree on the traditional 6oclock hold. Better to use a target that's not a traditional black center, blacken the sights and use a center hold. The eye naturally wants to center things don't fight it.

 

[Flint62Smoothie]

Well, it appears I 'agree to disagree' then. I stand by the teachings and results of 100s of 1,000s of open sight, highpower and competition shooters shooting out to 600-yards - world-wide no less - that has proven otherwise, in regards to a 6 o'clock hold versus a center or 'Navy' hold.

Your mileage may vary ...

 

[dave951]

Well, it appears I 'agree to disagree' then. I stand by the teachings and results of 100s of 1,000s of open sight, highpower and competition shooters shooting out to 600-yards - world-wide no less - that has proven otherwise, in regards to a 6 o'clock hold versus a center or 'Navy' hold.

Your mileage may vary ...

You're also conflating long range shooting with what the vast, vast majority of us do. Under 200yd, a center hold works far better than 6oclock. The size of the black should tell you something in regards to 100yd shots. Why would you want your rifle to hit 4in high from POA under 100? Most folks shooting muzzleloaders do not have rifles equipped with adjustable sights. Nor do they use a sling. Nor do they practice regularly. Nor do they stress over the smallest group possible. In short, apples to oranges. So yeah, YMMV.

 

[user 49399]

Thanks everyone. I believe the culprit was primarily resting the gun directly on the sand bag instead of in my hand on the bag. I knew better.

Also, but perhaps not as much was inconsistent loading.

 

[oldwood]

Ran into strange problem trying to sight a Jager rifle today. Got out of warm car and set the range up. Temp. was 40 deg. F. After 5 shots , the sight picture became slightly fuzzy. Found out this was due to thickening of eye mucus , lubrication. Went and warmed up again , some eye drops , cleanex and group tightened up again. Guess I'm just old. This was even using a diopter on my glasses. oldwood.

 

[dave951]

Ran into strange problem trying to sight a Jager rifle today. Got out of warm car and set the range up. Temp. was 40 deg. F. After 5 shots , the sight picture became slightly fuzzy. Found out this was due to thickening of eye mucus , lubrication. Went and warmed up again , some eye drops , cleanex and group tightened up again. Guess I'm just old. This was even using a diopter on my glasses. oldwood.

I've experienced this. Hydration levels can cause changes in visual acuity. Sweat running into the eyes is highly annoying when breaking a shot.

Like a good friend told me, getting old ain't for sissys.

 

[hanshi]

You mention that this T/C is your only rifle that does this. If you bench all of the rifles the same way then that's not likely the problem. Vertical stringing is often a sign of inconsistent velocities. Barring that the sights could be the culprit. I do not like to shoot in the open with the sun too far on either side as that causes front sight mirage. When sun makes the front sight glow it can throw off shots. The problem, however, is that horizontal displacement is the usual result. So it might really end up being your load or loading technique with this particular rifle.

 

[user 49399]

Yeah, it’s the only rifle that does this because it’s the only one I shoot from a rest. . I didn’t realize how I’d written that at first. I prefer to shoot all my other guns off hand. I don’t get vertical stringing when I shoot the T/C off hand. And since I don‘t get this problem with other guns shooting off hand it makes sense to me that resting the gun on the bag was causing the problem like dave951 pointed out. I learned this years ago but had forgotten about it since I normally shoot off hand.

I agree that inconsistent loading and velocities can cause it, but I’m usually careful to try to be consistent when loading.

 

[oldwood]

You might examine the shooting bench. 10 yrs ago , all the benches were taken when I went to sight my unmentionable . deer rifle I Only had to fire three shots , as it is never off. I fired two shots at 100 yds. , Rifle strung shots vertically. Shot a few more , and same vertical stringing. Left , right ok. Sat and thought just how my rifle might have became damaged , no answer. I got up to leave , and pushed on the shooting bench and , it moved back and forth . Changed benches to a stable one , and good to go. Shot out to 200 yds. all was perfect again Was the , in line , movement of the bench. Visited that range today , that particular bench is still no good. ..........oldwood

 

[Mark Herman]

Stringing shots can also occur based on where the rifle is rested, fore stock or barrel. That changes the barrel harmonics. Even the location on the barrel can change POI from one shot to the next. Be consistant.

 

[nkbj]

Vertical stringing is typically a sign of inconsistent burns which give inconsistent velocities.

 

[Canute Rex]

You might also try weighing your round balls. I had a "vertical barbell"pattern with one rifle and couldn't figure it out. Then it occurred to me that I was using a two cavity mold to cast the balls. Weighed the balls and there were two distinct weight ranges. Switched to one weight range and got one group. Now I use only one cavity of any two cavity mold.

Lee makes a six cavity mold. Use all six cavities and you might as well shoot with your eyes closed.

My standard practice now is to weigh all my cast balls and remelt the light ones.

Consistent patch lubrication is also important. I pre-cut patches and lube them all together in a container.

Plus what everyone else said.

 

[45man]

Your sights will "follow the sun". As it rises you will hit higher. Some time ago I tested a scope by mounting it to a bench and putting the crosshairs on the bull real early, As the sun rose to my left, the crosshairs went way left then up with the sun until very high, then moved across the paper way from the left to the right side and as the sun started down they went down the right side, back under the bull and eventually back to center.
With opens I have found myself shooting at a target that was not even where I seen it.
Bright front sights are the worst. Black is best and smoke them. Nothing worse the a sun sitting at the muzzle.

 

[Okie Hog]

Inconsistent mounting of the butt stock to the shoulder can cause vertical stringing. IME: It's more prevalent with Hawken stocks.

 

[dave951]

Inconsistent mounting of the butt stock to the shoulder can cause vertical stringing. IME: It's more prevalent with Hawken stocks.

Let's muddy that puddle even further, what you're wearing can have an effect. If you zeroed that gun in shirtsleeves but are shooting it in freezing temps with a heavy coat on, kiss that summer zero bye bye