Bullet string

Hog head · March 30, 2015, 09:50 AM

I'm in the process of finding the best load with my parts on hand and noticed a pattern of some vertical and some horizontal strings in my groups. What is this? Is it operator error or a function of velocity and bullet choice? At first I thought mabey I shot my groups too fast and it was barrel warpage then it changed directions. What gives? I don't think just dumb luck. It doesn't happen a lot just enough that I noticed it. Any thoughts?

Bart B. · March 30, 2015, 10:50 AM

Most of it is caused by the shooter. Us humans are typically not as repeatable as our rifles and ammo are. Nobody holding onto a rifle pulled into their shoulder will shoot bullets as precisely than the rifle clamped in a free recoiling accuracy cradle or machine rest. We don't hold them exactly the same from shot to shot. Of course, this assumes reasonable care in assembling hand loads as well as decent rifle parts fit.

If the barrel warps as it heats up, shots tend to string in the same direction each time.

What cartridge are you shooting at what range?

A .308 Win with a 100 fps spread in muzzle velocity will string bullets vertically about 2/10ths inch at 100 yards due to that much spread in bullet drop.

nemesiss45 · March 30, 2015, 11:22 AM

Sometimes it is shooter induced, and i may be caused by something seemingly inconsequential. For example, i have to quailfy with 3 weapons evey 6 months for work. I am pretty consistant about it, but last year, thinking nothing of it, i had several cups of coffee in the hours leading up to my range time. As a result, i was all over the paper.... still qualified, mind you, but obviously looser groups... all because the coffee made me a little jittery. I hadnt even noticed until i shot. Lack of sleep or foood can have an effect too.

Anyway... if you were getti g both verrical and horizonal strings, itd put it down to the shooter.... if it were consistently one of the other, maybe not.... but switching between the two suggest that neither is a hardware issue. Next time you shoot, try to be mindful of any shifts in body position or muscle tension... if something you arw doing is making a muscle tired it may give you stringing in one direction... then you shift a little, and the axist of movement changes, shifting the stringing.

**Unclenick** · March 30, 2015, 12:38 PM

Hog Head,

If you have a slender barrel, they can whip pretty significantly at times. Heating the barrel until it start making or increases firmness of contact of the barrel with the stock can cause a shift like that.

You didn't say what you were shooting at what range or in what wind conditions.

In general:

If your gun needs re-bedding to float the barrel, re-crowning, bolt lug lapping or receiver face truing, there's a limit to what you can tune ammo to.

If the gun is good to go, you can prove that to yourself by purchasing some commercial match ammo, assuming it is available for your chambering. Usually it's pretty darn good and makes a good way to tell if your loads or you and the gun are to blame.

Make sure your primers are solidly seated below flush with the case heads, at least two or three thousandths past the point where you feel the primer anvil's feet touch the bottom of the primer pocket. Any lesser depth can lead to ignition delays that are too short for most shooters to detect, but which act like slow lock time and cause velocity and barrel time variation.

If none of those things are issues, try shooting an OCW round robin or an Audette ladder if you have the range. See if you can't trace that muzzle vibration.

Hog head · April 1, 2015, 08:20 PM

Thank you for the two very interesting articles. To answer your question the rifle is a new dpms lr in .308 with a 16 or 18 inch barrel and I'm shooting at 100 yards for now. I think I will try the tests just for fun if those pesky responsibilities will stay out of the way but more than likely it was me and my less than spectacular shooting skills.

Doyle · April 1, 2015, 08:28 PM

Starting off with a very clean barrel can also introduce stringing. POI changes as the barrel slowly fouls until it stabilizes.

LE-28 · April 4, 2015, 06:33 AM

Doyle, I have that problem with handguns with as short as three inch barrels.

I'm sure your talking about rifles but your post kind of hit home.

I had a post on THR about this very thing happening to me and barrel warping, or the gun shifting in my grip were the only ideas offered.

I never thought about clean barrels. This does only happen to me after I have cleaned my guns.

Interesting.

Doyle · April 4, 2015, 05:40 PM

LE-28, think about it this way. Using a given bullet weight and load, a clean barrel is going to give you the least amount of pressure for that given load. As the barrel starts to foul, pressure is going to rise ever so slightly making successive bullets hit a little further up. After a few shots, the fouling stabilizes and the bullet POI remains consistent until the barrel starts to get really dirty.

That's my theory. I don't have any proof other than my own observation.

flashhole · April 5, 2015, 07:43 AM

My experience has been - vertical stringing is me not doing everything exactly the same at the bench. Horizontal stringing is my barrel heating up with short wait times between shots. I have two guns (Ruger #1V 25-06, Sauer 202 7mm RM) where the horizontal stringing is very predictable as the barrel heats up. Oddly enough, my 221 Fireball, 223 Rem and 45-70 don't exhibit stringing with a change in barrel temp but the POI will move around a bit depending on the outside temperature.

Here's an example of the 25-06 stringing horizontally with 5 shots fired in about one minute. Waiting for the barrel to cool between shots tightens the group up considerably.

March 30, 2015, 10:50 AM	#2
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	Most of it is caused by the shooter. Us humans are typically not as repeatable as our rifles and ammo are. Nobody holding onto a rifle pulled into their shoulder will shoot bullets as precisely than the rifle clamped in a free recoiling accuracy cradle or machine rest. We don't hold them exactly the same from shot to shot. Of course, this assumes reasonable care in assembling hand loads as well as decent rifle parts fit. If the barrel warps as it heats up, shots tend to string in the same direction each time. What cartridge are you shooting at what range? A .308 Win with a 100 fps spread in muzzle velocity will string bullets vertically about 2/10ths inch at 100 yards due to that much spread in bullet drop. Last edited by Bart B.; March 30, 2015 at 12:46 PM.

March 30, 2015, 12:38 PM	#4
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Hog Head, If you have a slender barrel, they can whip pretty significantly at times. Heating the barrel until it start making or increases firmness of contact of the barrel with the stock can cause a shift like that. You didn't say what you were shooting at what range or in what wind conditions. In general: If your gun needs re-bedding to float the barrel, re-crowning, bolt lug lapping or receiver face truing, there's a limit to what you can tune ammo to. If the gun is good to go, you can prove that to yourself by purchasing some commercial match ammo, assuming it is available for your chambering. Usually it's pretty darn good and makes a good way to tell if your loads or you and the gun are to blame. Make sure your primers are solidly seated below flush with the case heads, at least two or three thousandths past the point where you feel the primer anvil's feet touch the bottom of the primer pocket. Any lesser depth can lead to ignition delays that are too short for most shooters to detect, but which act like slow lock time and cause velocity and barrel time variation. If none of those things are issues, try shooting an OCW round robin or an Audette ladder if you have the range. See if you can't trace that muzzle vibration. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

April 1, 2015, 08:20 PM	#5
Hog head Member Join Date: March 26, 2009 Location: east TN. Posts: 66	Thank you for the two very interesting articles. To answer your question the rifle is a new dpms lr in .308 with a 16 or 18 inch barrel and I'm shooting at 100 yards for now. I think I will try the tests just for fun if those pesky responsibilities will stay out of the way but more than likely it was me and my less than spectacular shooting skills. __________________ The government is like a baby's alimentary canal,with a happy appetite at one end and no responsibility at the other............Ronald Reagan

April 5, 2015, 07:43 AM	#9
flashhole Senior Member Join Date: February 9, 2005 Location: Owego, NY Posts: 2,000	My experience has been - vertical stringing is me not doing everything exactly the same at the bench. Horizontal stringing is my barrel heating up with short wait times between shots. I have two guns (Ruger #1V 25-06, Sauer 202 7mm RM) where the horizontal stringing is very predictable as the barrel heats up. Oddly enough, my 221 Fireball, 223 Rem and 45-70 don't exhibit stringing with a change in barrel temp but the POI will move around a bit depending on the outside temperature. Here's an example of the 25-06 stringing horizontally with 5 shots fired in about one minute. Waiting for the barrel to cool between shots tightens the group up considerably. __________________ ,,, stupidity comes to some people very easily. 8/22/2017 my wife in a discussion about Liberals. Are you ready for civil war?

March 30, 2015, 09:50 AM	#1
Hog head Member Join Date: March 26, 2009 Location: east TN. Posts: 66	Bullet string I'm in the process of finding the best load with my parts on hand and noticed a pattern of some vertical and some horizontal strings in my groups. What is this? Is it operator error or a function of velocity and bullet choice? At first I thought mabey I shot my groups too fast and it was barrel warpage then it changed directions. What gives? I don't think just dumb luck. It doesn't happen a lot just enough that I noticed it. Any thoughts? __________________ The government is like a baby's alimentary canal,with a happy appetite at one end and no responsibility at the other............Ronald Reagan

March 30, 2015, 11:22 AM	#3
nemesiss45 Senior Member Join Date: February 6, 2014 Posts: 526	Sometimes it is shooter induced, and i may be caused by something seemingly inconsequential. For example, i have to quailfy with 3 weapons evey 6 months for work. I am pretty consistant about it, but last year, thinking nothing of it, i had several cups of coffee in the hours leading up to my range time. As a result, i was all over the paper.... still qualified, mind you, but obviously looser groups... all because the coffee made me a little jittery. I hadnt even noticed until i shot. Lack of sleep or foood can have an effect too. Anyway... if you were getti g both verrical and horizonal strings, itd put it down to the shooter.... if it were consistently one of the other, maybe not.... but switching between the two suggest that neither is a hardware issue. Next time you shoot, try to be mindful of any shifts in body position or muscle tension... if something you arw doing is making a muscle tired it may give you stringing in one direction... then you shift a little, and the axist of movement changes, shifting the stringing.

April 1, 2015, 08:28 PM	#6
Doyle Senior Member Join Date: June 20, 2007 Location: Rainbow City, Alabama Posts: 7,167	Starting off with a very clean barrel can also introduce stringing. POI changes as the barrel slowly fouls until it stabilizes.

April 4, 2015, 06:33 AM	#7
LE-28 Senior Member Join Date: September 24, 2012 Location: North Carolina Posts: 759	Doyle, I have that problem with handguns with as short as three inch barrels. I'm sure your talking about rifles but your post kind of hit home. I had a post on THR about this very thing happening to me and barrel warping, or the gun shifting in my grip were the only ideas offered. I never thought about clean barrels. This does only happen to me after I have cleaned my guns. Interesting.

April 4, 2015, 05:40 PM	#8
Doyle Senior Member Join Date: June 20, 2007 Location: Rainbow City, Alabama Posts: 7,167	LE-28, think about it this way. Using a given bullet weight and load, a clean barrel is going to give you the least amount of pressure for that given load. As the barrel starts to foul, pressure is going to rise ever so slightly making successive bullets hit a little further up. After a few shots, the fouling stabilizes and the bullet POI remains consistent until the barrel starts to get really dirty. That's my theory. I don't have any proof other than my own observation.