30-06 OCW Load Development Help

[stanley52]

I just got back from the range and I have a relatively good problem to have. I’m not sure where my OCW node is out of the 6 loads I shot - but most charge weights shot fairly tight groups. I used new Lapua brass, 185gr Bergers .012 off the lands, CCI BR2 primers, and IMR 4451 at: 54.0, 54.4, 54.8, 55.2, 55.6, and 56.0. I used 55gr for sighters at the bottom center target. My dilemma I run into is 55.2 and 56.0 seemingly have either pulls or flyers. I am by no means an expert marksman so unidentified pulls are definitely not out of the question. Assuming 56.0 has a pull, it has the exact same POI as 55.6 - which makes me think 56.0 is the center of a node - 56.0 is already several grains higher than any listed maximum for this combo, so I’m hesitant to go any higher though there are no pressure signs except the bolt is only ever so slightly harder to lift up but by no means “sticky”. I had 2 extra 55.0 sighter shells so i shot them at the middle top target at the end, so that is why there are only two holes there. Tell me what you all thin

 

[FURMAN]

I personally would reshoot 55.2 and 56 to make sure you were not the cause of the fliers. I agree with your line of thinking. If you did not cause them I would look at 54.6.

 

[stanley52]

I personally would reshoot 55.2 and 56 to make sure you were not the cause of the fliers. I agree with your line of thinking. If you did not cause them I would look at 54.6.

After further examination it appears 54.0 and 54.4 have the exact same POI then at 54.8 it shifts about 3/8"...which is really not that much but I'm not an OCW expert. There may be some potential to shoot 53.6, 54.0, 54.4, and 54.8 to see what's there.

 

[Shane Lindsey]

I would load 10 at 54.9. Shoot five for group and five over the chrono and see what it tells you. 54.8 has very little vertical as does your top sighters at 55 gr. Was the bottom 55 gr your first cold/clean shots?

 

[Dr. Vette]

You used new brass - note that your results may differ once your brass becomes once-used and enlarges a bit to fit your chamber.

I suspect that you can get a direction from this, but 55.2 may change to 55.6 as the best load next time around. Just an FYI.

 

[Mike 338]

You have the right idea that it isn't necessarily the tightest group but rather after you triangulate and find the center of the three shot group, which load of all the groups is more or less falls in the middle is the OCW. To me, 54.8 is close enough and just happens to be the tightest group as well. I'd say you simply skipped the "fine tuning" step and found a great load right away. As you can see in the heavier loads, your POI Center noticeably shifted to a degree that cannot be credited to shooter error.

I'd say you got a nice shoot'in load. The system works.

 

[FURMAN]

You have the right idea that it isn't necessarily the tightest group but rather after you triangulate and find the center of the three shot group, which load of all the groups is more or less falls in the middle is the OCW. To me, 54.8 is close enough and just happens to be the tightest group as well. I'd say you simply skipped the "fine tuning" step and found a great load right away. As you can see in the heavier loads, your POI Center noticeably shifted to a degree that cannot be credited to shooter error.

I'd say you got a nice shoot'in load. The system works.

I generally agree with this however I disagree that the heavier loads "cannot be credited to shooter error". If you remove the two fliers in the 55.2 and 56.0 groups I would guess you could cover 55.0-56.0 with a nickel. I think it would be unwise to discount the upper charges without, at least, a second look. I would actually be more worried about the 54.8 load because the 55.0 load jumps about an inch to the upper left. I still contend with the target provided and no shooter error 54.6 is where you will want to be.

 

[dsculley]

Many times when you run an OCW and you see a group with 2 rounds touching and a third flier it is due to shooter error. The rub is that is always the case. According to Dan Newberry, you will usually find nodes about 3% apart. If you can identify a scatter node, you can divide or multiply that charge by 1.015 to find the accuracy node. In your case, I suspect that 55.2 has a shooter induced flier. On the other hand, 56 does look like a scatter node. If you do the math using 56 as the scatter, that points to 55.2 (or near there) as the accuracy node. That is supported by your target if the flier at 55.2 was shooter induced.

As was said earlier, depending on the size of your chamber and how much the brass grew on firing, the actual node could change. Measure your fired brass and compare it to new brass to see how much it grew. Just remember that it usually takes 3 firings to completely fire form brass to a chamber. When I am working up a new load, if I start with new brass I will not finalize a load until I have had the brass through at least 3 cycles. When I built my 6.5x47 I used a piece of new brass to head space the barrel and set the barrel for .002" clearance. With this set up, I get nearly identical performance with new and fire formed cases.

Once I have settled on a charge, I will load three rounds of that charge and three rounds each at +/- 0.1 gr from that charge. I shoot three groups using 1 of each charge weight per group. If all three of those groups are within my predetermined parameters then I am finished with load development. I may tweak seating depth at that point. (I will have run the Berger seating depth test before starting load development so I know my seating depth should be close.)

 

[stanley52]

I would load 10 at 54.9. Shoot five for group and five over the chrono and see what it tells you. 54.8 has very little vertical as does your top sighters at 55 gr. Was the bottom 55 gr your first cold/clean shots?

The bottom 55gr were the first 3 shots, but it was not a clean bore. I had scrubbed it shiny clean and then shot 5 previous to this to foul the barrel a bit - they were not shot at a target.

 

[stanley52]

Many times when you run an OCW and you see a group with 2 rounds touching and a third flier it is due to shooter error. The rub is that is always the case. According to Dan Newberry, you will usually find nodes about 3% apart. If you can identify a scatter node, you can divide or multiply that charge by 1.015 to find the accuracy node. In your case, I suspect that 55.2 has a shooter induced flier. On the other hand, 56 does look like a scatter node. If you do the math using 56 as the scatter, that points to 55.2 (or near there) as the accuracy node. That is supported by your target if the flier at 55.2 was shooter induced.

As was said earlier, depending on the size of your chamber and how much the brass grew on firing, the actual node could change. Measure your fired brass and compare it to new brass to see how much it grew. Just remember that it usually takes 3 firings to completely fire form brass to a chamber. When I am working up a new load, if I start with new brass I will not finalize a load until I have had the brass through at least 3 cycles. When I built my 6.5x47 I used a piece of new brass to head space the barrel and set the barrel for .002" clearance. With this set up, I get nearly identical performance with new and fire formed cases.

Once I have settled on a charge, I will load three rounds of that charge and three rounds each at +/- 0.1 gr from that charge. I shoot three groups using 1 of each charge weight per group. If all three of those groups are within my predetermined parameters then I am finished with load development. I may tweak seating depth at that point. (I will have run the Berger seating depth test before starting load development so I know my seating depth should be close.)

I think I am going to re-shoot 54.4, 54.8, 55.2, 55.6, 56, and add 56.4.

I'm competent but not an expert shot. There was a full value 0-4mph wind that I never compensated for, so shots could shift left/right up to .3". Shooting these charges again should confirm with certainty if there is a scatter node at 56.0-56.4 and if there is an accuracy node at 54.8-55.2.

 

[stanley52]

For those interested:

I do not have a picture, but I re-shot all 6 original loads. I ended up with 55.2gr. 54.8, 55.2, and 55.6 has the exact same POI when I re-shot. All 3 of these groups were less than .5 MOA. 55.2 also had a perfect clover leaf with rounds completely overlapping - estimating to be a .3" group. Not even going to bother messing with seating depth. .012 off the lands seems to work just fine...

Next time I go to the range, going to check ES over chrono and then do a 600 yard velocity vaidation!

 

[FURMAN]

For those interested:

I do not have a picture, but I re-shot all 6 original loads. I ended up with 55.2gr. 54.8, 55.2, and 55.6 has the exact same POI when I re-shot. All 3 of these groups were less than .5 MOA. 55.2 also had a perfect clover leaf with rounds completely overlapping - estimating to be a .3" group. Not even going to bother messing with seating depth. .012 off the lands seems to work just fine...

Next time I go to the range, going to check ES over chrono and then do a 600 yard velocity vaidation!

Exactly as I suspected. Good job.