Range Report What would cause this pattern?

[Autofire]

I was at the range the other day and below are my two targets. I shot two sets of 22 rounds (2 sighters and 20 rounds) using my AIAT with a 6.5 Creedmoor Barrel. I was shooting from 600 Yards. Although I am extremely happy with the results, I just cannot figure out what would cause this type of pattern not once but twice. Any Ideas?

 

[Rust]

I'd say variations in velocity is the most likely culprit. With a 140 gr bullet (Hornady for instance) at 600 yards, a 100 fps variance in velocity will give about 6" vertical, or about 1.2" for every 20 fps. This based on a muzzle velocities of 2800 to 2700 fps. At 1,000 yards that would be about 25" for the same 100 fps spread or about 5" for every 20 fps.

You'll need to do a little chrono work to determine what sort of (if any) velocity variations you have. Your horizontal dispersion is excellent which leads me to believe it is not rifle related but load related. Are you shooting factory ammo or handloads. If it's factory it's time to look at handloading. If your handloading then you'll need to work on your process especially precise powder measurement.

Regards

 

[Autofire]

I did not realize that 20fps would make that much difference at 600 yards. I am handloading using H4350, 41.10 grains of powder. My weight variance (I get lazy on picking out individual grains of powder) 41.08 to 41.14. my extreme spread is typically around 30 fps.

 

[Milo 2.5]

What size are the rings on the target? I think it is your fundamentals as far as how you manipulate the rifle for a lack of a better term. Focusing for 20 shots is something I may struggle with. Your horizontal spread is awesome for 600 yards.
Plus by your charge weights, doubt it is in the load.

 

[6brshooter]

What was mirage doing?

 

[Autofire]

The rings are X=3", 10=6", 9=12". The mirage was light to medium boiling.

 

[6brshooter]

It could be vertical from poor sd/es, but barring that, I'd say you got hung out to dry by mirage

 

[Racer88]

Hmmm... I'm no expert, but I find the nearly absolute lack of horizontal dispersion to be quite unlikely, especially with 22.... rather 44.... shots at 600 yards.

I'll be the first to say it, I guess... but, I'd suspect a problem with the e-target system. Something ain't right.

Even the pattern from top to bottom is nearly identical for both targets. It's a shallow "S" shape. No way that's right. The e-target gizmo is out-of-whack. If you trace a line through the shots, it intersects the x-ring at the exact same spots (at the top and bottom of the x-ring), for both targets. The chances of you shooting the exact same pattern, twice... with 22 shots.... at 600 yards is infinitesimally remote.

 

[Mordamer]

Hmmm... I'm no expert, but I find the nearly absolute lack of horizontal dispersion to be quite unlikely, especially with 22.... rather 44.... shots at 600 yards.

I'll be the first to say it, I guess... but, I'd suspect a problem with the e-target system. Something ain't right.

Even the pattern from top to bottom is nearly identical for both targets. It's a shallow "S" shape. No way that's right. The e-target gizmo is out-of-whack. If you trace a line through the shots, it intersects the x-ring at the exact same spots (at the top and bottom of the x-ring), for both targets. The chances of you shooting the exact same pattern, twice... with 22 shots.... at 600 yards is infinitesimally remote.

I was going to leave this same comment last night, but there was a problem with my browser. There is no way his horizontal dispersion is that small at 600. Chances are that his group was wider than tall, but only one axis on the shot marker is working.

 

[Autofire]

Hmmm... I'm no expert, but I find the nearly absolute lack of horizontal dispersion to be quite unlikely, especially with 22.... rather 44.... shots at 600 yards.

I'll be the first to say it, I guess... but, I'd suspect a problem with the e-target system. Something ain't right.

Even the pattern from top to bottom is nearly identical for both targets. It's a shallow "S" shape. No way that's right. The e-target gizmo is out-of-whack. If you trace a line through the shots, it intersects the x-ring at the exact same spots (at the top and bottom of the x-ring), for both targets. The chances of you shooting the exact same pattern, twice... with 22 shots.... at 600 yards is infinitesimally remote.

According to the Shot Marker's designer Racer88 you are correct. He says I quote "The sensors are plugged in wrong. If you swap top right and bottom right, you get a horizontal line pattern. No way for the system to tell the difference."

Thanks for the feedback all!