How would you read these OCW groups?

I'm trying to find the OCW for my 6.5cm and it's proving to be elusive, most likely due to my ignorance. Am I on the right track with this picture? I chose one seating depth, based on a promising* group I previously fired.

H4350
41gr-42.5 in .3gr increments
CCI BR2 primers
Hornady brass
142gr ABLR
**41gr group was too high, so I manually adjusted/punched 2" down after adjusting my scope 2" for the rest of the groups. You can see the evidence of the pasters above it.
Where should I go from here?

your 41.6 looks good try .2 lower and .2 higher take the best one and play with seating depth this is what I would try and have you done any brass prep

Play with seating depth @41.6

Thanks—I feel like I've been reading a lot, but not absorbing. I haven't done any brass prep, save for trimming.
I'm kind of back to the drawing board with this. I've done several pressure tests up to 42.5gr and feel like there is more room to go higher. Velocity at 42.5 is ~2700fps.

Am I understanding that an OCW test will identify where any* bullet will shoot well in a gun or will there always be bullets that are just difficult to shoot well?

you are close on velocity you cannot go by book velocity as they were testing your rifle and were not at the place you are altitude and temp wise I believe you are on the right track if you do want more speed try the rl-26 powder if you have it

I've got RL26, but was going to save it for my 7mm Rem and 6.5PRC. I'm ok with the slower 2650-2700 speeds with the high-BC ablr, as long as I can get it consistently sub-moa. But I might also try some loads above 42.5 and see where I max out pressure-wise, and see if there's another node. The 42.5gr load had them all within .25 vertical, but strung out horizontally, as you can see. Does that indicate anything?

I just can't see anything consistent as far as centers of the groups are concerned, vertically.

the444shooter said:

I've got RL26, but was going to save it for my 7mm Rem and 6.5PRC. I'm ok with the slower 2650-2700 speeds with the high-BC ablr, as long as I can get it consistently sub-moa. But I might also try some loads above 42.5 and see where I max out pressure-wise, and see if there's another node. The 42.5gr load had them all within .25 vertical, but strung out horizontally, as you can see. Does that indicate anything?

I just can't see anything consistent as far as centers of the groups are concerned, vertically.

Click to expand...

I feel like I'm in about the same boat you are. I was shooting off a bipod and rear bag and was told to put that stuff away until my load development was done. I'll resume testing this weekend with the following changes that have been made since my last range outing: shooting off a bench rest bag (much better repeatability for me), trigger weight reduced, action screws re-torqued (or torqued depending on how you look at it, they were not torqued to manf. recommendations). I'm not good enough or consistent enough with a bipod to shoot for groups with any level of confidence.

the444shooter said:

I've got RL26, but was going to save it for my 7mm Rem and 6.5PRC. I'm ok with the slower 2650-2700 speeds with the high-BC ablr, as long as I can get it consistently sub-moa. But I might also try some loads above 42.5 and see where I max out pressure-wise, and see if there's another node. The 42.5gr load had them all within .25 vertical, but strung out horizontally, as you can see. Does that indicate anything?

I just can't see anything consistent as far as centers of the groups are concerned, vertically.

Click to expand...

Did you run a full seating depth test prior to shooting this? I think that the reason that things are a little wonky may be because you are off of the seating depth a little. The group at 41.6 with the single flyer could be an indicator that everything is just about right but not perfect, this charge looks to be in the middle of a node. The node to me looks between 41.3 and 41.9 and you may be coming back into something with the 42.5 group and you may want to explore above that depending where you are with pressure. I would tweak seating depth with the 41.6 charge.

I've ran tests at multiple charge weights, multiple seating depths, nothing really getting me where I need to be. An earlier test at 41.9gr for seating depth had me at 2.840 showing the most promise. I saw/read that seating depth changes should be done in .003" increments, so I did 2.837 for the groups shown above. I can't tell which variable to change at any given time. But I guess I'll try to tweak the seating depth

I chose 41.9gr in the test because the velocities were the most consistent. **Although, upon further research, I learned that consistent velocities don't mean diddly squat, and I might've wasted all the effort due to faulty reasoning**
See these groups below from my seating depth test at 41.9gr
41.9gr H4350 Seating Depths varying by .010 (before I read that it should be done at .003 increments)
Going clockwise, starting from bottom left, 2.820, 2.830, 2.840, 2.850, and then I tried 2.898 and 2.895 because I was jammed at just over 2.900 and I had learned about the .003 increments. As you can see, 2.840 showed potential. What I don't understand is why seating depth caused so much change in vertical spread, with the same powder charge. Or maybe it's shooter-induced?
Also, looking at the groups going from 2.830, 2.840, then 2.850 does that give any indication of which direction I should start adjusting the seating depth?

To simplify things, only change one thing at a time. That's less confusing and you can better tell what effect you're having.
Most people work powder charges up first, then adjust seating depth last.
Getting a good node is all about barrel harmonics.
Get close to what your rifle likes for a charge first. Then tweak seating depth.
Seating depth also affects harmonics - and that's where you fine tune. It is common for different seating depths to produce different groups.
If you can't get the vertical out tweak your powder one final time (usually a little lower charge).
Finally, try a different primer. Sometimes that makes a surprising difference.

Did you shoot your OCW with the 2.840 seating depth? I have seen numerous seating depth test targets show similar results to what you have posted, vertical and horizontal groups just like that. I am actually surprised that you continued through the OCW after the seating depth test that produced that group... I would have chalked the flyer up to 1 to many coffees and proceeded to go shoot a group at 1000 to see how it held up. I will say in my early years of reloading I spent way to many bullets trying to shoot small groups with low es/sd at 100 yds.

With OCW you're looking for the powder charges that have the least change in the center of the group, the theory being that the center of the groups will change less with variations in shooting conditions and cartridge components.


Assuming that your target was at 100 yards, I ran a quick evaluation of the groups through my OnTarget TDS software. If you look at the group markups you will see a small cross in the center of the group box, that's the center of the group. What you want to find is the groups that have the least difference between where that cross is in relation to your point of aim. So assuming that your point of aim was the center of each dot the least change was between the 41.6 and 41.9 powder charges. I'd recommend working your next loads between those powder charges. I'd also stick with the 2.840" seating depth. It looks to me like you should get your best 100 yard groups using around 41.6 grains of powder and a seating depth of 2.840". If that proves to be true then I'd test at longer ranges and see if the group sizes and center points perform as expected.

No, I shot the OCW w/ 2.837 COAL. I derived the 2.837 from the promising group that 41.9 @ 2.840 showed. I'm really trying to figure out the baseline to start from. In watching the video from Ryan Furman that you showed me, he suggested seating depth test first, so that's what I was trying to establish with the varying seating depths at 41.9, and it led me to 2.840

Thank you, everyone. Like I've said to several of you, I feel like I'm learning just enough to confuse myself.