OCW Results: Any Help is appreciated

[Podigga]

First time running the OCW test. Looking for help determining best node/ load. Would really appreciate everyone's help.

Rem 700
26" Barrel
Lapua Brass
CCI 450 Primer
Lapua Scenar 139gr.
.010 off lands.
100 yards.

MV
39.0 - 2679.
39.5 - 2705.
40.0 - 2735
40.5 - 2761
41.0 - 2785
41.5 - 2819
42.0 - 2847

Thanks guys!

 

[cschaub]

In my short OCW experience I would say the node is 40.5-41.5g. The center's of the 3 groups are roughly in the same spot.
People say that you shouldn't really pay attention to group size. But I do to a point. I first try to find 3 diff charge weights that have a common group center POI. When I find the 3 charge weights, I change the middle charge weight by a couple tenths plus and minus to determine if the group sizes open up or shrink. I'd suggest try 40.8 and 41.2g and go from there.
My guess would be it'll end up 40.5-40.8 because the 41.5g charge opens up a bit
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[Podigga]

Thanks, Cschaub! This is very helpful.

 

[pell1203]

Try looking at range of 40.5-41.0 in more detail. Maybe break it down to 0.1 gr steps as in, 40.6, 40.7, 40.8, and 40.9. Your velocities at these charges are reasonable and won't kill the life of your barrel.

If there is a higher velocity node it will be somewhere above your highest target at 42.0. Make sure you check pressure signs if you decide to go this way.

 

[padom]

Did you record each shots velocity? If so go online and input the 3 velocities for each charge weight into an SD calculator and report back. That helps confirm the correct charge weight with low SD numbers. Ignore group size right now. A seating depth test will shrink that right up.

40.0g now do seating depth test to shrink group size.

41.0 POI shifts to 11 oclock vs the previous 3 groups POI at 12 oclock.

 

[AuburnBLK]

What charge is top left group? Maybe I can't see - apologies

 

[FishDr]

My first look was exactly what Padom said above. Listen to his experience…

 

[Podigga]

Did you record each shots velocity? If so go online and input the 3 velocities for each charge weight into an SD calculator and report back. That helps confirm the correct charge weight with low SD numbers. Ignore group size right now. A seating depth test will shrink that right up.

40.0g now do seating depth test to shrink group size.

41.0 POI shifts to 11 oclock vs the previous 3 groups POI at 12 oclock.

update:
First group was (4) cold bore fouling shots. Magnetto Speed chrono attached and tightened every 4-5 shots.

MV Avg
39.0 - 2679 - 2665, 2689, 2684 SD: 12.6
39.5 - 2705 - 2703, 2701, 2713 SD: 6.4
40.0 - 2735- 2736, 2739, 2731 SD: 4.0
40.5 - 2761 - 2769, 2757, 2758 SD: 14.0
41.0 - 2785 - 2776, 2784, 2797 SD: 10.5
41.5 - 2819 - 2819, 2820, 2820 SD: 0.5
42.0 - 2847 - 2839, 2839, 2850 SD: 6.3

The higher SD could have been the load prep all things considered?

 

[CharlieNC]

The point of impact is too similar such that you did not achieve enough differentiation between the charges. Back up to 200yd an re-shoot, you need to observe distinct changes in vertical in order to find the node where poi is least affected.

 

[Podigga]

The point of impact is too similar such that you did not achieve enough differentiation between the charges. Back up to 200yd an re-shoot, you need to observe distinct changes in vertical in order to find the node where poi is least affected.

Thanks Sarg!

 

[Darkside-Six]

update:
First group was (4) cold bore fouling shots. Magnetto Speed chrono attached and tightened every 4-5 shots.

MV Avg
39.0 - 2679 - 2665, 2689, 2684 SD: 12.6
39.5 - 2705 - 2703, 2701, 2713 SD: 6.4
40.0 - 2735- 2736, 2739, 2731 SD: 4.0
40.5 - 2761 - 2769, 2757, 2758 SD: 14.0
41.0 - 2785 - 2776, 2784, 2797 SD: 10.5
41.5 - 2819 - 2819, 2820, 2820 SD: 0.5
42.0 - 2847 - 2839, 2839, 2850 SD: 6.3

The higher SD could have been the load prep all things considered?

looks like you have 2 nodes. first one at 39.5-40 and the 2nd at 41.5-42.

If it were me and I really wanted to tighten it down I'd start with the higher node because it's a bit faster. I'd load up 5 round groups at 41.5, 41.6, 41.7, 41.8, 41.9, and 42.

Shoot them in random order over a chrono and right down the average MV, SD, and ES. i'll bet you find somewhere in between 41.5 to 42 you'll find it tighten right down.

 

[Brentc]

I see a scatter node at 40.0. Normally in OCW testing you'll see triangle groups with two shots fairly close together with one extending out coming from a previous POI or indicating the next POI. The exception to this is the scatter node because it produces spread out groups with no shots hitting close together. Therefore, since 40 is your scatter, your OCW accuracy nodes should end up at 40.6 and 41.8. When you do an OCW make sure your increments are small enough to capture the trends. .5 grains isn't small enough to catch the best POI trends especially for a 40 grain case. You have to figure each of these accuracy nodes are approximately .5 grain wide. If your increments are too large you could miss some key trend information. Try .3 or .4 grain increments next time you test. I don't use larger than .4 grain increments on even my largest magnums.

Take a look at the link below and see what Dan says about the scatter group and reference the photos.

http://optimalchargeweight.embarqspace.com/#/ocw-vs-ladder/4529811360

 

[Podigga]

I see a scatter node at 40.0. Normally in OCW testing you'll see triangle groups with two shots fairly close together with one extending out coming from a previous POI or indicating the next POI. The exception to this is the scatter node because it produces spread out groups with no shots hitting close together. Therefore, since 40 is your scatter, your OCW accuracy nodes should end up at 40.6 and 41.8. When you do an OCW make sure your increments are small enough to capture the trends. .5 grains isn't small enough to catch the best POI trends especially for a 40 grain case. You have to figure each of these accuracy nodes are approximately .5 grain wide. If your increments are too large you could miss some key trend information. Try .3 or .4 grain increments next time you test. I don't use larger than .4 grain increments on even my largest magnums.

Take a look at the link below and see what Dan says about the scatter group and reference the photos.

http://optimalchargeweight.embarqspace.com/#/ocw-vs-ladder/4529811360

Thanks for your help. Everyone here has been very helpful.

I'll reshoot next week with smaller spreads in weight. I'll post results.

Thanks guys!