Why horizontal stringing? 30-06 with high BC bullets

[clearwater]

A load that previously was giving nice 3 shot sub moa groups. Some sub 1/2".
This time I got an 1 1/2"+ horizontal string and much higher and varied velocities.

The variables
1. This time tried magnum primers
2. set my bipod on a slick piece of fabric like my benchrest online friend recommended
3. had a 5 mile per hour side wind


previous velocities with winchester primers were 2600 fps
This time they climbed almost 200 fps!
Didn't even try the 1/2 grain greater load

Can a five mile an hour wind move a bullet that much in 100 yards?
Am I so over pressure I am getting wild variations in velocity? Brass, primers and extraction all seemed normal.
Is a slick fabric under the sticky rubber bipod caps a good idea?

 

[SJB358]

Something is out of wack. nearly 2800 with SB6.5 is getting up there.

Yeah a 5 mph breeze can for sure move a 2MOA load that much at 100 yards.

 

[Firebird24]

I’m going to disagree. 212 gr eld x should not shift in 5mph wind at only 100 yards. The biggest flag I see is that you are using new brass rather than once fired. I do prefer a solid rest and never use a bipod for load work up-

 

[Ralt71]

What's on the end of the barrel of this rifle?

A 200+ grain .308 bullet should not move that much in 100 yard with only 5mph wind.

Your speeds seem really fast for a 30-06 with this size bullet in it as well.

 

[Bruce Mc]

I'm guessing it's the magnum primers and the increased velocity they created.

 

[RL338]

5 mph wind should show less than 1/2” at 100yds.
A bi-pod that’s not being preloaded on a slippery surface is not ideal for load development.
Anytime a variable is introduced into a load , I start from scratch.
2 years ago I picked up some CCI 250s and they were a pain when used in my 338WM.

 

[xphunter]

A load that previously was giving nice 3 shot sub moa groups. Some sub 1/2".
This time I got an 1 1/2"+ horizontal string and much higher and varied velocities.

The variables
1. This time tried magnum primers
2. set my bipod on a slick piece of fabric like my benchrest online friend recommended
3. had a 5 mile per hour side wind

View attachment 29287
previous velocities with winchester primers were 2600 fps
This time they climbed almost 200 fps!
Didn't even try the 1/2 grain greater load

Can a five mile an hour wind move a bullet that much in 100 yards?
Am I so over pressure I am getting wild variations in velocity? Brass, primers and extraction all seemed normal.
Is a slick fabric under the sticky rubber bipod caps a good idea?

It wasn't the wind.
Were you shooting off of a bi-pod in previous range trips, when it was shooting good?
I wouldn't use a slick fabric myself with a bipod, unless it was something like my JOYPOD-X...Which is a completely different cat.

JOYPOD-X

The JOYPOD-X was designed for F-TR, but it is also being used in different rimfire and air rifle disciplines, and it is being used for F-Open at times. It comes in various colors as seen below. …

sebrests-usa.com

 

[wvbuckbuster]

You changed several variables it seems. My guess is the bipod rest setup and possible primer change. Go back to what your previous load and rest setup was and see if your groups go back to the same size as before.

 

[xphunter]

Yep

 

[clearwater]

I think the primers.

The velocities were wild. I still have a few dozen of the load that shoots good.

What I got last time

I'm going to try them again and chrono.

Didn't like the slick fabric anyway, it made it hard to get everything centered for the next shot as the gun moved so much.

The bipod has helped all my other shooting so far.

The wind wasn't that strong, but I don't really have a model or experience to judge how much it effects things.

 

[xphunter]

I think the primers.

The velocities were wild. I still have a few dozen of the load that shoots good.

What I got last time
View attachment 29315


Didn't like the slick fabric anyway, it made it hard to get everything centered for the next shot as the gun moved so much.
The bipod has helped all my other shooting so far.

I was guessing the gun was moving a lot from shot to shot. Any inconsistency in form would make the rifle recoil differently and therefor effect groups.
When working on fundamentals, it is very important to really focus on hand (And the amount of force or energy you are gripping the stock with) and trigger finger positioning (Consistent press and not jerking anticipating recoil), and that stock is in your shoulder pocket the same every time.
If, you have all this down, my apologies for bringing it up.

I actually do a lot of load development with a bi-pod.