Vertical string with a hot rifle barrel, what about horizontal?

[Jenrick]

Vertical stringing as a rifle heats up, is nothing new. Does anyone know of an instance where a hot barrel leads to horizontal stringing?

My Mk 4. No1* holds steady at about 1"-1.5" of horizontal spread with my preferred loads at 50yds when warm. It also does about the same cold. I've never heard of horizontal spread as the barrel warms. Is there any reason I should suspect that the horizontal spread will increase as the barrel warms up beyond warm?

Vertically it strings about 2"-4" as the bore warms up, and is an honest 2" gun at 100 yds if I let the bore stay cool.

-Jenrick

 

[primalmu]

I would think the vertical spread is a result of gravity. As the barrel warms up it expands and would change the point of impact. If you think about it, assuming a free floating barrel, gravity is the only force that is acting on the barrel. *shrugs*

 

[boommer]

vertical stringing is lack of recoil control and horizontal stringing is lack of trigger control as a rule. If you see a gun patterning one way or other start looking at what your doing. I've learned that from shooting long range black powder cartridge rifles, were it takes almost 3 as long for a bullet to leave the barrel as to a 30-06, so everything is more extravagant. Just because this is one rifle that doing this to you, could be the fit of the rifle to you.

 

[Andrew Leigh]

Vertical stringing (roughly on the axis 06:00 to 12:00);
Breathing control, too hard a front rest causing the forearm to bounce, firing pin problems causing erratic strikes.

Horizontal stringing (roughly on the axis 09:00 to 15:00);
Action not sufficiently tight in the stock, wind, forearm slipping on front reat, trigger control, front rest surface slippery, poor bedding.

Horizontal stringing (roughly on the axis 10:30 to 16:30);
Pulling the trigger, canting the rifle

Horizontal stringing (roughly on the axis 08:00 to 14:00);
Forcing the shoulder into the butt.

 

[Hummer70]

To be sure if you have a chronograph see what your extreme spread is. For instance shoot and chronograph first ten, get a sub total average quickly. then shoot another 10 and get subtotal average for second string.

I am assuming you are talking vertical at short range? It could be improper or no stress relief of barrel, barrel pressure from stock, marginalfiring pin energy will show vertical stringing right before you get to the misfire area but mostly shows at long range.

I had a Ruger 77 that shot flat string 9 to 3 and then I lapped bolt lugs as bottom one was not touching at all and it started shooting round groups when both contacted evenly.

I have also seen loose optics in internal adjustment scopes cause such. Shake scope to see if you hear something loose.

At ranges like 600 yards boiling mirage will cause vertical stringing.

When shooting military sights not focusing on front sight will give vertical stringing.

I am sure there are others but this is what what I have seen happen.

 

[Art Eatman]

Generally, I've found that vertical stringing comes from some problem with the barrel and forearm bedding. The steel expands slightly as it heats and thus there can be a change in pressure on the barrel. Shooter error would be if the point of rest of the forearm on the front sandbag isn't consistent.

Generally, horizontal stringing--if everything is tight--comes from a bit of canting from shot to shot. It doesn't take much to show up on the target.

That's pretty much been my experience, anyhow.

 

[murf]

if you are talking about barrel heating only, that is a bedding issue. stock pressure on one side of the action and/or barrel, and not the other.

murf

 

[Warp]

I would think the vertical spread is a result of gravity. As the barrel warms up it expands and would change the point of impact. If you think about it, assuming a free floating barrel, gravity is the only force that is acting on the barrel. *shrugs*

...what?

 

[Andrew Leigh]

...what?

So it was not only me that was left a little confused .......

 

[Warp]

Vertical stringing (roughly on the axis 06:00 to 12:00);
Breathing control, too hard a front rest causing the forearm to bounce, firing pin problems causing erratic strikes.

Horizontal stringing (roughly on the axis 09:00 to 15:00);
Action not sufficiently tight in the stock, wind, forearm slipping on front reat, trigger control, front rest surface slippery, poor bedding.

Horizontal stringing (roughly on the axis 10:30 to 16:30);
Pulling the trigger, canting the rifle

Horizontal stringing (roughly on the axis 08:00 to 14:00);
Forcing the shoulder into the butt.

Vertical stringing (what you listed in bold), if shooting unsupported (such as prone while using a loop sling for support) is often breathing + support elbow not directly under the rifle.

 

[Welding Rod]

A hot barrel may string in any direction, just depends on where the stress is in the barrel.

 

[TNBilly]

I'm with Art for the most common of causes but also add to vertical stringing... if the rifle is still new lock-up break-in will can cause it till it wears in.