Horizontal stringing

[thumper3181]

I recently bought a Bergara B14 HMR in 300WM and I am reloading for it. I am using Gunwerks virgin brass, 195 Hornady ELD Match, IMR 4955 powder, Winchester LRM primers and all loads are .020 off the lands l. I tried to do an OCW for it off a bench with a bipod and a rear bag and for some reason the last two charge weights that I shot had horizontal stringing.
Everything was still torqued tight so I don't think that anything was moving, so would it be a load issue or could it be something to do with the nut behind the butt?

 

[INTJ]

Given how your other groups look I would think load. That said, the only way to know for sure is to test again. Preferably from front and rear rests vs a bipod unless you are very good at shooting small groups off a bipod.

 

[Fast14riot]

I also think load is the cause. Ive had a couple rifle do that. One went from groups, to a perfect horizontal string about 1.5moa wide on the next charge, then to a perfect vertical string, then back to groups. Was pretty strange to see.

 

[RegionRat]

@thumper3181 it could be some of both like INTJ is saying. Hard to say with any confidence after just looking at a photo to be able to eliminate anything knowing just those facts.

For starters, how far was that target? If it was only 100 yards, it says you have to try what INTJ said and work on your bench technique without the bipod till we get things sorted out.

If it was 300 yards, and there was gusts of wind, it could explain the horizontal for example.

If you were only 100 yards, it could still be the load and technique at the same time. Bipods and stocks have added their share to mysteries, you will have to try and eliminate some variables if possible.

Is there any other load or ammo this gun has shot better?
Have you ever been able to bench shoot into <MOA in your background?

 

[Dusty Stevens]

You got windflags out?

 

[JohnKielly]

Back a while in Australia when we shot military ammo in our fullbore rifles, we would tune the group by incrementing the foresight on the barrel. It was virtually normal to see a group go from horizontal stringing to pinhole (to the capacity of the ammo) to veridical, or vice versa, as the sight was moved.

Tony Boyer talks of tuning his groups for a bit of vertical in his book. Maybe he has this concept in mind.

 

[thumper3181]

Groups are at 100 yards and I can shoot MOA off of a bench with most of my other rifles including my Rem model 7 in 300SAUM, but I don't shoot a lot off of the bench. The wind was a little gusty, but at 100 yards I wouldn't think that it would have little to no effect. I was working up loads and shoot off a bench in order to chronograph for velocity. I've loaded up a few more of the 71.8gr and few more 74.2 I'll try groups with it prone tomorrow.

 

[daniel brothers]

for horizontal groups..... adjust seating depth.

for vertical groups... adjust powder charge

first get consistent low ES by adjusting powder charge.... then adjust seating depth. If you don't first get low ES charges...then all else is chasing your tail. Where it hits on the target is not as important as FIRST getting low ES charges.

 

[chromatica]

Horizontal stringing can be a sign of trigger control problems.

 

[chromatica]

Trigger control problems are accentuated as recoil increases with hotter loads.

 

[LHSmith]

A 20 mph crosswind will move a 190 gr. (pushed @ 3000) 1" @ 100. Plus factor in the barrel may have been heated and caused mirage which caused the target to appear to move horizontally which could easily account for the extra inch. Use some type of wind flags (even if it's just flagging on a stick) and use a mirage shield (or let barrel cool more between shots) to minimize the unknowns.

 

[Coyotefurharvester]

I would try with front and back bags, with one of the same loads. If the group changes, the stock is probably an issue.

 

[RegionRat]

Groups are at 100 yards and I can shoot MOA off of a bench with most of my other rifles including my Rem model 7 in 300SAUM, but I don't shoot a lot off of the bench. The wind was a little gusty, but at 100 yards I wouldn't think that it would have little to no effect. I was working up loads and shoot off a bench in order to chronograph for velocity. I've loaded up a few more of the 71.8gr and few more 74.2 I'll try groups with it prone tomorrow.

Sounds like a plan. You have the background from the other posts with regard to technique and wind related patterns. Just remember bipods can be a great field tool, but that takes as much practice or more than bag rests.

If you took a look at a charge weight Ladder run and saw any potential at all, then pick one of those and do a seating depth adjustment like @daniel brothers suggested.

In a 100,000 foot view, try and select a charge weight that looks like a node or with evidence of a low SD/ES and then try to run the seating depth sweep in a similar way as a charge ladder. (sounds like an oversimplification if there ever was one...)

If you are lucky, you will find a couple of depth steps that cluster together (up down and left right). I try and run these types of Ladder tests at my maximum distance, but do what you can. Try and avoid blustery days, but don't over think the wind, just be honest and use flags if at all possible so you can study what happens as you pull the trigger.

If you are lucky, you will find the node for charge weight that gives good distance potential, and the seating depth the gives the tightest "round" groups. I have a feeling you have read articles and heard all this before.

Some folks use bbl tuners and some don't. The old Browning HOTS system did work on carry guns when the charge weights and bullets were the "right ones".

 

[jackieschmidt]

From a Benchrest shooters point of view, you are simply going through different vibration nodes as you change the charge.

There is a misconception that a rifle that is shooting horizontal is in tune. That is not necessarily true. Granted, it could be in tune and being a victim of conditions.

Which leads us to wind flags. Once again, as a Benchrest shooter, I never shoot without flags. It’s been my experience that the majority of casual shooters have no concept as to how much ye wind pushes bullets around, even big ones.

I agree with the suggestion of getting the ES and SD at a comfortable spot and then work with the seating depth. After the actual powder charge, I believe that seating depth is the single most important factor in getting the rifle in tune.

I use tuners on my Benchrest Rifles. It allows me to avoid that dreaded horizontal tune, which by definition is bullets going left or right when you are sure the conditions did not warrant it.

 

[rijndael]

FWIW: I have seen horizontal stringing with my loads, during workup, and I'm 100% sure there was no wind. It was an indoor 100Y range.

 

[Webster]

Given how your other groups look I would think load. That said, the only way to know for sure is to test again. Preferably from front and rear rests vs a bipod unless you are very good at shooting small groups off a bipod.

I use a bipod on my Varmint rifle and shoot small groups. It's difficult without a total BR gun and serious rest. After every shot I have to reposition the rifle, rear bag and bipod. I think the bipod legs have to be locked all the way forward. When setting up I mark on the bench with a magic marker the bag position and where the bipod legs contact the bench. Also I slide the rifle forward and back rotating the rear bag so the cross hair moves verticle on the target. Aligning the bag V grove.

How do you deal with recoil? That's a big powder charge. It's been 35 years since I had a 7MM Rem Mag. I don't know how I would deal with recoil now at my age. With my 6BR and 6BRX I can see the cross hair move on the target when the gun goes off so I guess I don't have any obvious flinch.

 

[JFrank]

I recently bought a Bergara B14 HMR in 300WM and I am reloading for it. I am using Gunwerks virgin brass, 195 Hornady ELD Match, IMR 4955 powder, Winchester LRM primers and all loads are .020 off the lands l. I tried to do an OCW for it off a bench with a bipod and a rear bag and for some reason the last two charge weights that I shot had horizontal stringing.
Everything was still torqued tight so I don't think that anything was moving, so would it be a load issue or could it be something to do with the nut behind the butt?

Looks like your shots are following a clock face also as you change the set up from bull to bull.
Plus a smart fella told me to always use a wind flag.

 

[Shooter13]

The wind was a little gusty, but at 100 yards I wouldn't think that it would have little to no effect.

That sir is a total misconception.

 

[Dusty Stevens]

That sir is a total misconception.

Mr Smith above in post #11 gave an example of one that is pretty stable comparatively and it showed a gust of 20 (which is not unheard of ) may move a 190 over 1”. Factor in a rifle already shooting 1/2” on its best case and you could have an impact an inch and a half away. Get a gust the other way on the wrong side of the group and you could shoot a 3” group with zero shooter or rest error. Gotta use wind flags before you can make ANY conclusions on a load

 

[Richard Coody]

Mr Smith above in post #11 gave an example of one that is pretty stable comparatively and it showed a gust of 20 (which is not unheard of ) may move a 190 over 1”. Factor in a rifle already shooting 1/2” on its best case and you could have an impact an inch and a half away. Get a gust the other way on the wrong side of the group and you could shoot a 3” group with zero shooter or rest error. Gotta use wind flags before you can make ANY conclusions on a load

I agree with Dusty about the effects of wind. That is the great equalizer. Learning to read the wind is an art that takes years to develop. Tail winds, quartering winds, head winds all effect your groups differently. That is why in benchrest runners are most common. They try to get all their shots off before conditions change.

That said when I am doing load development at 100 yards I try to pick a calm day. Relatively common here in south GA especially early in the morning. I have found that the shape of groups changes with small changes in seating depth. Goes from horizontal to circular to vertical. Now these are small changes and you need a precision rifle to see them. I would try small changes in seating depth in both directions and see what the target tells you.