Stringing

[Unknown]

I had always understood that vertical stringing usually meant that the load has insufficient powder...usually needing just a wee bit more. In a Sako TRG22 I'm using Lapua 170 grain lock base bullets, CCI BR2 primers, LC75 brass all match prepped and sorted by weight, and 43.5 grains of Varget. At 200 yards I get vertical stringing around 2-2.5 inches high by 1 inch horizontal. C.O.A.L. is 2.825. I tried a C.O.A.L. of 2.810 and accuracy improved as the rounds were longer. 2.825 is the max length that will fit into the DPMS LR308 mag, and the FNAR mag.

What I don't understand is the same load in an FNAR strings the same load horizontally by almost exactly the same amount.. It is as if the groups were turned 90 degrees.

My LR308 loves the load and shoots 1.5 inches at 200 yards, mostly with some vertical stringing, by about 1 inch wide.

All groups shot during the same weather conditions within about an hour of each other.

Other than this simply being a load that one rifle loves, and two other rifles don't really like, does anyone have any suggestions?

I have done the ladder testing, and chrono'ed the load. I worked up to it slowly, and have tried some loads of 43.5 grains Varget with the same components...the results weren't much different.

With the TRG22 at 43.5 grains of Varget, primers are beginning to flatten some...about 80% of the primers have lost some of the roundness on the edges, but aren't really "crushed", and bolt lift is only occasionally beginning to get a little sticky. Most folks wouldn't notice the change in bolt lift, but I know it is just starting, so I think 43.5 is getting close to as hot as I really want to try.

Does anyone have any suggestions?

 

[ChrisGarrett]

Re: Stringing

Try different bullets.

Your Sako should shoot better than MOA, unless you're either not a great shot or the barrel is somehow 'off'. At 200 yds, I would think it's more a shooter's issue, vs. a velocity thing.

Your other guns are shooting MOA it seems, or better and people need to realize that putting bullet after bullet into the same hole, isn't all that easy.

Why one weapon shoots that load wide and another shoots it tall, is just the nature of the beast.

Start fiddling with other combos and see.

Chris

 

[Unknown]

Re: Stringing

The Sako has aways been a good performer with almost any bullet. I'm thinking I'll have to play around with seating depth for this rifle to get it shooting good. I bought 1000 of the Lock base bullets because I have always had good luck with them.

I am pleased that the LR308 loves this load, as it has been a famously picky rifle, and to find a load that shoots about .75moa at 200 yards in that rifle was wonderful. With that in mind, I'll play with seating depth for the Sako and see what happens.

This is the first time my Sako has acted like this, so I'm guessing it is something pretty basic. As my velocity is in the correct range for this bullet, and the extreme spread and standard deviations are reasonable (although not terrific), my bet is that seating depth will be the key..I'll try these loads with different seating depths and see what happens.

 

[iplumb]

Re: Stringing

I've had great success with 46 of Varget, Lapua brass 210 primers and 155 scenars in my trg22. I use 2.850 OAL. Recently hit 12" x 12" steel at 1740 yards.


I have a FNAR - and I think the factory trigger leaves alot to be desired, night and day from a trg. I wonder if the trigger pull is getting you the horizontal spread?

Mike

 

[ChrisGarrett]

Re: Stringing

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Unknown</div><div class="ubbcode-body">The Sako has aways been a good performer with almost any bullet. I'm thinking I'll have to play around with seating depth for this rifle to get it shooting good. I bought 1000 of the Lock base bullets because I have always had good luck with them.

I am pleased that the LR308 loves this load, as it has been a famously picky rifle, and to find a load that shoots about .75moa at 200 yards in that rifle was wonderful. With that in mind, I'll play with seating depth for the Sako and see what happens?

This is the first time my Sako has acted like this, so I'm guessing it is something pretty basic. As my velocity is in the correct range for this bullet, and the extreme spread and standard deviations are reasonable (although not terrific), my bet is that seating depth will be the key..I'll try these loads with different seating depths and see what happens. </div></div>

Try bumping the velocity up slightly, or down a bit to look for the accuracy nodes. Try different brass, if you have it, like some Winchester or Lapua and begin to rule things out. Try different powders too.

I would think you might be able to get up to 45+grs of Varget and still be fine, but maybe work the powder a bit.

You should be able to get that 170 LB up to 2700+ fps out of a TRG-22.

Chris

 

[Hummer]

Re: Stringing

Are these being shot bench rest? With or without a bipod? Monopod? Rear bag? Bench technique has ruined many a group.

 

[Unknown]

Re: Stringing

Bipod front, sandbagged rear. Same technique that worked well before the stringing started.

I realize that each rifle is different, but I have experimented with sandbagged front and rear, and the results are the same. I was starting to wonder if my elevation turrets have finally gone loose from years of use...

 

[ReaperDriver]

Re: Stringing

Try eliminating as many other issues besides the loads. For example: re-torque all your scope rings and bases back to spec. Check for anything loose, like the stock. I had some aggravating stringing show up out of nowhere and it turned out to be the scope rings had loosened up slightly.

Another issue is your cheeckweld or head position. If you are going back and forth between two completely different rifles (TRG-22 and the LR308) which require completely different shooting positions - its most likely you aren't getting a correct or consistant cheekweld with one or both. Again, I had the same problem happen when I put a new scope on the same rifle. The new scope was a 56mm Obj where as the old was a 50mm - so the new required higher rings. For a solid two weeks, I struggled with vertical stringing until I added some padding under my stock pack to raise my cheekweld - and the stringing completely went away.

 

[jhead7416]

Re: Stringing

Usually when I develop verticle stringing, it was mostly inconsistant loading of the bipod.

 

[SWRichmond]

Re: Stringing

My 700P pushes shots up the target as it warms up. As in, 4 or 5 shots warm. Proved it today by drastically slowing down, and stopping after each 3 shot group.

 

[Shady_Jay]

Re: Stringing

Vertical stringing is sometimes indicative of your breathing cycle.

Horizontal stringing is sometimes indicative of finger placement on the trigger.

I would check those first before adjusting the load.

 

[Grump]

Re: Stringing

Am I the only guy who's noticed that those group sizes are for 200 yards?

We're talking fine-tuning here. Regardless of whether/how many other that Mr. "better than MOA" above also misunderstood, the suggestions are all good.

When chasing what Bill Alexander calls "the accuracy demon", continued stringing or "two-grouping" problems need to be evaluated also in terms of what shot number in the group is going where. If you are not able to see AND plot on paper each shot, being brutally honest in your shot calls*, then you need to shoot each shot on an separate bull.

Despite the TRG's stellar reputation and typically boringly reliable accuracy performance, if you got the one bad barrel in a thousand (or whatever) that walks shots up or down as it warms up, that's a step necessary to find that out.

Shot-by-shot analysis like that can also uncover shooter fatigue/concentration issues or physical causes for small declines in performance (1/4 to 1/2 MOA deviations from normal group). Bipod loading as suggested above, anything that starts happening somewhere into a *string* as opposed to how the first two shots behave.

Detailed testing of this sort, with Chrono numbers cross-referenced, is one more measure I would recommend. If your regular loads are getting 100 fps spread despite your load development being only 20 fps ES, you gotta know if that is making shots hit high or low or whether there is no correlation at all.

Then of course of your barrel is just no better than that and oddly enough has more vertical than horizontal error, and the opposite for the other rifle mentioned.

More data needed to isolate the problem.

Enjoy the chase!



*None of this "I called that one a half-inch left so I'll disregard it even though it is out of the group by an inch and a half" stuff.

 

[SWRichmond]

Re: Stringing

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SWRichmond</div><div class="ubbcode-body">My 700P pushes shots up the target as it warms up. As in, 4 or 5 shots warm. Proved it today by drastically slowing down, and stopping after each 3 shot group. </div></div>

I failed to note, my other LRR, a .300WSM, doesn't exhibit this behaviour. Much heavier aftermarket barrel. No stringing.