Vertical stringing

[LHSmith]

If it's not a rest induced problem (make sure your "BR type" rest is not pinching the stock), look to the powder charge. Record temp. at each session because it does affect velocity. Just to eliminate potential causes, make sure you use a mirage shield.

 

[conor m]

fast , have you stripped down and cleaned the bolt and the trigger assembly . i know that this can cause a slight variation in the lock time which inturn can cause vertical.
strip both down and see if this helps.
conor m

 

[Macropod]

You might have a dud barrel.... It happens sometimes...

Usually the group tends to be sporadic but not always. I found that out the hard way.

Often a bad barrel will prove difficult to develop a load for (hmm... no kidding). And if you do find a load that sort of works, it will still go off tune. Finding this out is gold, it is getting to the discovery point that drives you nuts...

 

[savagedasher]

Is the barrel free floating? If it is try putting it in a rest . Then check it. Too hard rear bag of front causes vertical. Beading can also make problems. The rear bolt behind the trigger can be too tight.
I adjust vertical with powder charge. Larry

 

[RandyM72]

My latest experience, which Ive put a few barrels on over the last year. Anyhow, I had my action re-trued by another smith and my barrel set back the last go around. Took it out with the same loads that had previously held 3/4in groups at 300 and the gun wouldn't hold a MOA. I went home and got my reloading gear and headed back to the range to re-tune my load thinking this was the problem. (This is my F-Class gun that has won a few comps and placed 3rd in Master class at Berger Nats) On the way back to the range I started thinking about the possibilities of what was going on with the load when I remembered about my Savage hunting rifle, which is bone stock. I remembered that after working up a good load with that rifle I started messing around with torque settings on the action screws and actually tightened my groups up by a whole inch at 300 yards. So I decided to try this on my F-Class gun before going back through and redeveloping a load. I brought my front screw up from 45in lbs to 51in lbs and my rear from 45in lbs to 48in lbs and BINGO!! It went right back to shooting 3/4in groups. Just food for thought!!

I too have had the same experience. With epoxy bedding that covers the first 2 inches of the barrel, I think the action screws torque becomes more critical. I had a sako 243 varmint and the best it would shoot was 3/4" MOA. I loosened the forward action screw tension and the groups shrank by 1/2. I was stunned. Stringing can be caused by varying pressures that can be identified with a chronograph to check for consistent velocities. Inconsistency in bullet seating depth, neck tension, powder charge, headspace, bedding - all these can cause variances in pressure/velocity. If a barrel is NOT free-floated, consistent placement of the forward rest becomes more important. Small barrel diameters can cause vertical stringing when overheated. I would glass bed my rifle to start, regardless as I do with all my rifles. It becomes a process to find the culprit.

 

[LCazador]

Have you tried a faster burning powder like H4350. I did a 243 Improved back in early 90's and 4831sc didn't work. Try a different powder. We have such great options nowadays.

 

[Big Mc]

What is the most common cause for vertical stringing in groups?

I had an action trued and new bbl installed and am having a heck of a time getting vertical string tuned out.
Ive had it in 2 different stocks, tried various seating depths, different primers, free recoil and firm grip technique and no luck yet.

My next try will be a different scope. Just curious as to what the pros here have found to cause this to happen.

Stock problems. !!!!

 

[Fuj]

This target shot yesterday testing a new bullet with just 2/10ths grain of
N-135 between each 3 shot group. Upping the charge took the vertical
out and replaced it with horizontal. Now I will play with seating depth to
reduce the horizontal.

 

[Fast14riot]

OP states it started ok after group testing, then got worse, also states nearly 300 rounds on the barrel. I bet an anti-node was picked and now the barrel has sped up, pushing him to a between the nodes situation.

Shoot a powder charge test with 3 round groups with ~1% steps in charge weight at a horizontal string of aim points at 100y. Look for the groups that print highest above poa. That will be close to your stable load. You can always fine tune between the steps if you like later, but the target should look like this.