Weird Group

[bob_dobalina]

I don't claim to be a good shooter, I'm just a hunter. But what do you think about this 5 shot group?

I think it's 3 stacked in one hole, 2 in the other. The thrown shot could just be one, the target may have had a little bend, but I don't think so all others made nice .308 bullet holes.

What do you think about the thrown shots? Anything I can adjust loading or is this all to blame on my technique?

The thrown shots are the first and the last. The last bullet I had seated too deep and had to pull out a hair with a collet puller and reseat so that may have affected neck tension.

Another concern I have is this load goes to hell with a few more tenths of a grain, very finicky.

 

[DrMike]

That is not an unheard of occurrence. The group could fall within standard deviation and still give you such an aberration. When a load is that finicky about charge weight, it might indicate that you are near or over the maximum charge for accuracy. The maximum chamber pressure could be safe, but the charge is right at a node. You might try giving a bit more jump to the lands to see if that tightens the group. If the velocities are presenting a low ES, giving more jump to the lands is the way I'd go.

 

[mjcmichigan]

I think you have 4 in the bigger group and one that .. maybe you rushed a little or was just a flier.

Good shooting.

Groups like this are evidence of attention to detail and a patient shooter.

Great Job.

BTW, dead critter on all 5 shots.


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[noslerpartition]

About the bullet seated to deep and pulled:
I have to neck size after pulling bullets.
Don't know if that's true if you pull just a little, but after taking bullets out some cases wouldn't hold the bullet anymore without resizing the neck.
Might explain one of the flyers.
The other one?
What DrMike said.
One group of five holds a lot of statistical error. Which could actually have worked in favour of the group...

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[bob_dobalina]

That is not an unheard of occurrence. The group could fall within standard deviation and still give you such an aberration. When a load is that finicky about charge weight, it might indicate that you are near or over the maximum charge for accuracy. The maximum chamber pressure could be safe, but the charge is right at a node. You might try giving a bit more jump to the lands to see if that tightens the group. If the velocities are presenting a low ES, giving more jump to the lands is the way I'd go.

I did the ladder workup to pick the load; 63.6 and 63.8 were velocity dups so I went with 63.7. However, when I shot it again through a chrono I was 66fps lower than before, but with a completely clean, cold barrel, so who knows.

I did kind of a seating depth work up too but my jumps were pretty big.

.11" off of the lands is as close as I can get 'em with my magazine.

So I did

.11, .16, and .22 off. .22" off shoots really well for me with TTSXs believe it or not so I thought I'd try it out. Well .11" off was the best of the lot, .16" wasn't bad, .22" was bad. I've shot .19" before (book COAL) and it wasn't good either. I could try seating deeper with more micro adjustments though? Any suggestions?

I think you have 4 in the bigger group and one that .. maybe you rushed a little or was just a flier.

Good shooting.

Groups like this are evidence of attention to detail and a patient shooter.

Great Job.

BTW, dead critter on all 5 shots.


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Or one is off the target! No, I thought about what you're saying too - tough saying. I would be happier with a larger 5 shot group than the flier, maybe I just need to try again.

Thanks guys, for the advice.

 

[bob_dobalina]

About the bullet seated to deep and pulled:
Which could actually have worked in favour of the group...

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Yep I agree, I think I need to shoot it a bit more

 

[Nimrod84]

Good group, shooting again is a great idea. Whole lot of environmental factors I don't know about. For example, that fps drop you experienced would indicate that you came out of the node... But, without knowing your setup, I can't really comment here - personally, I get about 50fps variations between sunny and cloudy readings with my Oehler 35p optical chronograph.

Likewise, have you heard the term, lights up / sights up or sun up / bullet down? As weather conditions change our sights and eyes will interact differently so that shots land in different locations when the brain says we have the same sight picture. So if you had significant light variations on the target (cloud cover at the first and last shot but sunny for the middle three) it could explain the two groups. Most writing on this is for iron sights, but it does apply to optics as well.

From a load standpoint, I would second what Dr. Mike wrote and suggest seating bullets a hair deeper (0.12-0.15") along with considering upping the charge to 63.8 grains if you think temperature played a role in that 66 fps drop.

Rule of thumb I've used for years is that if the groupings are a large equilateral triangle, seat the bullets out a 1/4 turn on the die and repeat until the group shrinks. If the group is 2 together with the 3rd out there, seat the bullet deeper in the same manner, a 1/4 turn at a time and the group will shrink.

I think you might be seeing two groups resulting from bullet length to ogive variations - I've had this happen a few times. But neck tension, or environmental sensitivity of the load are still solid contenders. The solution, if bullet variations is your problem, is to find a seating depth that tolerates bullet variations. That or sorting bullets... I would highly suggest seating the bullets a little deeper before sorting them.

 

[bob_dobalina]

Good group, shooting again is a good idea.

I would second what Dr. Mike wrote and suggest seating bullets a hair deeper (0.12-0.15") along with considering dropping the charge weight down to 63.6 if it goes sideways with a few tenths of additional powder, or go up to 63.8 grains if you think temperature played a role in that 66 fps drop.

Rule of thumb I've used for years is that if the groupings are a large equilateral triangle, seat the bullets out a 1/4 turn on the die and repeat until the group shrinks. If the group is 2 together with the 3rd out there, seat the bullet deeper in the same manner, a 1/4 turn at a time and the group will shrink.

I suspect that you are seeing two groups resulting from bullet length to ogive variations - I've had this happen a few times. The solution, if this is your case, is to find a seating depth that tolerates bullet variations. So try seating a hair deeper or re-visit that 0.22" jump. It might be more tolerant of bullet length to ogive variances than the 0.11" jump; even if it provides a little less precision.

Thanks I'll seat a bit deeper. I did try 63.8 and it shot about the same. These will be my last 5 bullets until my order comes in. Turns out reloading supplies are still hard to get!

 

[Nimrod84]

No problem. I did revise my post to add some environmental considerations as well and press home the value of re-shooting to verify the loads double grouping.

The lights up / sight up situation took me a few years to really understand. I see about a 1" to 1.5" vertical difference at 100 yards with iron sights or with low power scopes (2-3x) between the target being brightly and dimly lit. Higher magnifications like 12-15x I don't see much difference.

 

[bob_dobalina]

Do you ever feel like there are too many variables? Haha I sure do.

 

[DrMike]

Do you ever feel like there are too many variables? Haha I sure do.

That is what ensures hand loading is an enjoyable pasttime.

 

[mjcmichigan]

It’s like hunting...you never get there. It’s the journey


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