Vertical stringing.

[JeffinNZ]

Team.

What are the usual causes of vertical stringing? I know about inconsistent ignition.

Shot the Pygmy today and it has thrown it's toys out of the cot. Groups at 100m of 1.5 inches wide and 6-8 inches tall!

No changes in loads. Charges, alloy, seating, primers and sizing all the same.

Could I have some lead fouling?

[Whitespider]

The two most common causes of vertical stringing;
1) Inconsistent bench rest shooting technique (the shooter)
2) Velocity variation (the load)

Shooting technique will have more effect at slower bullet velocities (like cast boolit loads) due to the extended barrel time.

Velocity variation won’t usually have an 8-inch effect at 100m, unless boolit velocity is dropping through the sound barrier during flight.

[leftiye]

Maybe neck tension, or crimp variations. Also, maybe powder position sensitivity with a small powder charge in a larger case.

[NuJudge]

I'd worry about sight picture and shooting technique (particularly sling tension in rifles) also. Focusing on the front sight for one shot, then focusing on the target for the next will lead to vertical stringing.

Shooting several shots, altering position while reloading, then firing more shots will result in a change in point of impact. I don't notice much difference off the bench, but I sure do while in a sling, except when really careful.

CDD

[Char-Gar]

Pressure on the barrel from high places in the stock forend can cause stringing as well.

[BudRow]

Barrel heating?

[mag_01]

Vertical stringing can also be caused by leading where parameters are exceeded such as boolit hardness -- Fit ---Lube --- Powder charge ---- Ambient temperature --- Have experienced this when trying to push A load too hard. ---- Mag_01

FWIW Have also seen this with J--bullets in the 7.62x39 where one type of ammo would string vertically to one O'Clock and others of different manufactures would shoot good groups --- Same gun -- same day --- off the bench.

The best group that day was shot with military surplus --- Don't remember the head stamp --- I still have 3 or 4 different head stamps in millsurp. (7.62x39)

[montana_charlie]

Loose sights...

[SNELLN2]

http://www.6mmbr.com/verticaltips.html

This site has some good tips. Good luck, Al.

[Bullshop]

One of the problems with the SMLE that does cause verticle stringing is the way the forend/hand guard is hung on the barrel. If you pinch the barrel and forend between thub and finger you will see how much flex there is between bottoming out top to bottom, or the distance between touching the bottom wood and touching the top wood. Each time you shoot this flex ocurs. If there are any bumps, ridges, or tight spots on the hand guard wood that cause a varrying return of the barrel when it comes to rest this can result in verticle stringing. Since we are looking at a round channel it generally has an angle to the string in one direction and not perfectly verticle. The top metal and wood has to be a perfect fit to the barrel contour. If there are any tight spots they must be corrected. My fix is bedding both the top and bottom in two sepperate operations. After this is done and the pinch test done ther is no longer any flex. This is just the way I have delt with the verticle stringing inherant to the SMLE. Good or bad right or wrong this is how I have solved the problem for myself.
BIC/BS

[charger 1]

Pressure on the barrel from high places in the stock forend can cause stringing as well.

Anyone who's owned a ruger one knows all about that. I never knew just how severe vertical stringing could get until I owned a ruger one, and shot it hot without accurizing the front

[Shiloh]

Loose sights...

Don't discount or ignore this. Happened to me!! Boy did I feel both dumb but relieved when I discovered it!!

Shiloh :castmine:

[jtaylor1960]

I have seen this with loads that don't fill the case with certain powders. Pressure will also cause this as the barrel heats up.

[crowbeaner]

The gremlin of vertical stringing usually rears it's head because of inconsistent primer strike. Main causes are inconsistent primer pocket depth(need uniforming), a weak or "set" firing pin spring, or leaving the firing pin cocked and storing the rifle in the cocked position. If all else checks out I'd check the spring to see if it needs to be replaced. Check the forearm if your gun has one and be sure it is tight. Check your sight screws, and bases if you have them. Make sure your gun is nestled into the bags, and your hold is the same for each shot. Make sure you squeeze the trigger. Clean your barrel and make sure the crown is not dinged. Make sure your ammo is not in the sun to avoid extreme shot to shot variations (important with WW 748 powder). Just some of the gremlins helpers to watch out for. Enjoy. CB.

[JeffinNZ]

Hi team.

All good ideas and thanks. I have cleaned the barrel with Ed's Red and it appeared not to be fouled with lead. Work it over hard with solvent and a bronze brush to clean out the carbon etc.

Sights are tight, check. Have experienced loose sight before so good idea.

Loads are 90-100 load density so not powder position. Shooting Benchmark (BM2) and H4350 (AR2209).

NUJudge has me thinking on the focus thing. I have been guilty of this before and I am shooting a bead front an rear peep. Good post.

Barrel is pressure pointed but this has not changed. Even warm in the past has not been a problem.

Loaded more rounds tonight and will shoot them Thursday and report.

Thanks again team.

[charger 1]

Well I really cant see a peep giving a vertical string, but who knows. I still say pressure. Even if you know its not a heat contact thing I'd look at the possibility of not comming back to rest the same each time. But I'd bet its pressure weather from within or outside but one of the two

[ace1001]

You should be able to slide a dollar bill under the barrel of a bolt action all the way to the action. If not that, look for unburned powder in the barrel. If your pressuer is not enough to ignite all the powder, you don't really know how much you burn each shot. Ace

[scrapcan]

Not all rifles need to be free floated. some do quite well having full length bedding. I have seen more than my share of m70 winchesters that shot crappy when free flaoted and did much better when full lenght bedded. Also seen a lot of remingtons that had the pressure point removed form the foreend and did worse than with it still there.

Not everything is a set answer, just keep that in mind.

As for JeffinNZ issues, I have no idea. Might want to review what the weather conditions were. Maybe your stock has soaked up some extra humidity causing pressure where it was not before.

You must let us know what you find.

[RU shooter]

If it has been wet or very humid where you are at it may have put different pressure on your barrel and changed harmonics of barrel? Maybe try small shim under barrel at end of lower handguard.Cant hurt to try a little more upward pressure since that is what enfields like anyways. Also As far as you it could be inconsistent cheek weld/head position, I was dealing with this issue shooting high power last year using a AR15 and was loosing shots both high and low 8's and 9's in prone slow fire. It was all how I placed my head/cheek on the stock each time just a very small amount differently. Now I have resolved this issue and am shooting in 190's this year.

[JeffinNZ]

SUCCESS.

Turns out my barrel had done gone got fouled up with a HEAP of carbon and a wee bit of lead.

I scrubbed the living daylights out of it with solvent and JB's in addition to subjecting it to my electro bore cleaner until it was spotless and HEY PRESTO, accuracy has returned.

I am now counting the number of shots I put down the barrel and will monitor the count at which accuracy turns again.