New 7 rem mag, horizontal stringing.

[timberbuck]

Have a new Rem 700 long range in 7 mag I just started working with.

Installed timney trigger, 2 lbs.
Glass bedded recoil lug+first 1" of barrel, rest of barrel free floated.
Seekins 20 moa pic rail, vortex precision matched rings.
Sightron S3 LRIRMOA 6x24x50

Everything torqued and checked. Reticle, gun and elevation turret level.

Found a couple factory loads it likes all ready (around 1/2-3/4 MOA at 200 yards).

With factory loads that it does not like the groups are always strung horizontally, never round in shape or vertically strung.

Need I be concerned?

Thanks.

 

[LaHunter]

.5-.75 MOA at 200 yards with factory ammo is pretty dang good. If your rig will do that with factory ammo, I don't think you have anything to be worried about with your rifle, IMO.
Just out of curiosity, how wide is the horizontal stringing and is it more to the left or to the right?

 

[Punisher]

How are the primer strikes on your shell? I have always thought that an off center strike can actually translate into a slower ingnition time and slow the powder burn... If you slow that burn time, you can generate higher pressure. That will not only move your bullet vertically, maybe only slightly, but change the harmonics in your barrel.

In the end, the changes you are seeing is a result of the harmonics and temperatures applied to the barrel. Changing powder types, primer types and seating depth all play a role in this.

There is no easy answer. In fact, all of us have been searching for the reason behind these anomalous groups.

The only thing you can take as FACT, is that some loads just shoot better in that gun than others.

 

[timberbuck]

The bad groups are 1.5 to 2 MOA wide. Seems most are to the right.

 

[roninflag]

for my guns the horizontal is caused by wind. vertical is the gun/load.

 

[Azprc]

How are the primer strikes on your shell? I have always thought that an off center strike can actually translate into a slower ingnition time and slow the powder burn... If you slow that burn time, you can generate higher pressure. That will not only move your bullet vertically, maybe only slightly, but change the harmonics in your barrel.

In the end, the changes you are seeing is a result of the harmonics and temperatures applied to the barrel. Changing powder types, primer types and seating depth all play a role in this.

There is no easy answer. In fact, all of us have been searching for the reason behind these anomalous groups.

The only thing you can take as FACT, is that some loads just shoot better in that gun than others.

Are you saying that an offset struck primer moves the groups horizontally?

 

[Punisher]

Not really, I'm saying that I think it could change the harmonics of your barrel. That may result in a group shift in any direction.

 

[Azprc]

Isn't the pin offset gonna be fairly consistent with the same gun?

 

[Punisher]

Where the pin hits in relative to the gun stays the same. the pan in the primer has little holes in it too. that will vary on each shot. i'm saying that i believe that an offset primer hit could change the burn rate of the powder- this changing the harmonics of the barrel. primer strike will be consistent, But accuracy won't be consistent between different loads.

 

[Unofficial Gun Addict (UGA)]

Hey Timberbuck... There's a couple of things I've noticed over time which causes stringing... Improper bedding, stock to barrel contact (this could be only under recoil), action screw tension, and barrel heating. There's no mention as to whether your groups are coming from a cool barrel.

I'm making the assumption that your first shot of the day is always true... And subsequent shots start stringing horizontally.

I suppose the easiest to remove from the list is action screws and after that, verifying that there's no chance that the stock is touching the barrel when pressure is applied to it. the easiest way to see if it's barrel heat, is to take a cold bore shot. Wait 10 minutes or so (depends on the ambient temperature), and take another... And so on.

If you're still getting horizontal stringing... Then I'd check the bedding... And after that is sorted, if you are still seeing horizontal stringing... Stop taking beer to the range!

Oh... This might sound silly... But one time we were trying to suss out this issue, it was actually the scope... And it was our first trip to the range with it so we had not verified first true cold bore shot. It was A Simons mag44, but you have an excellent optic, so I doubt that is the problem.

 

[moombaskier]

My $$ is on how you are holding the rifle. Make sure it recoils straight back and use the same amount of shoulder pressure on each shot.

 

[Unofficial Gun Addict (UGA)]

My $$ is on how you are holding the rifle. Make sure it recoils straight back and use the same amount of shoulder pressure on each shot.

Good point moombaskier... I should never forget marksmanship fundamentals when addressing other peoples issues. I tend to think...if this rifle was stringing horizontally for me... The things I wrote would be what I would check, but I'm really OCD with my shooting... So it wouldn't have even occurred to me to look at fundamentals. Good call man!

-James

 

[snowpro440]

Post a picture of your target and we will see if we can help you .....Give us the details .

 

[timberbuck]

The problem has gone away.
Barrel is now broke in. Two fouling shots from a clean bore and taking time to make sure each shot is a cold bore shot.

Thanks