Need help interpreting OCW test results

[hunter67wa]

I wait 2 minutes in between shots. I think 41.6 and 42 would be good places to look.

Good luck

 

[loosefur]

I appreciate all of the input. I got hung up looking for three graduations that grouped similarly. There aren't three that group similarly, but there is a pair that groups similarly: 40.8 and 41.2. Thanks for pointing that out guys. I'll play around in there some more.


Berger gave me load data for this powder/bullet combo and had 42.3 as max. I exceeded that by 0.1 grains in my top load. The primers still looked good with no signs of pressure. They had rounded edges, not a hint of flowing primer, no ejector swipe or hard bolt lift. I can't help but wonder what lies beyond. I'll focus on 41 for now because it shows potential, but I may come back and push it more.

 

[ShtrRdy]

I'm amazed at how good all the groups are. Good luck with the fine tuning.

 

[loosefur]

I'm amazed at how good all the groups are. Good luck with the fine tuning.

Thanks. Yeah, it's proving to be a shooter, even with factory ammo. I got it off the used rack at a gun shop. My first load test was with 140 eld-ms and H4831sc and one of the powder charges produced this 3-shot group. I loaded up more of that charge weight and attached the chrono and got this 4-shot group. It's a little slow but that's to be expected with that powder. I wanted to get more eld-ms but couldn't find them so I went with the Bergers.

 

[Doom2]

I wait 2 minutes in between shots. I think 41.6 and 42 would be good places to look.

Good luck

Down South here in the summer it's more like 4-5 minutes! Some guys have even started to use bore fans on bolt actions.

 

[ShtrRdy]

Thanks. Yeah, it's proving to be a shooter, even with factory ammo. I got it off the used rack at a gun shop. My first load test was with 140 eld-ms and H4831sc and one of the powder charges produced this 3-shot group. I loaded up more of that charge weight and attached the chrono and got this 4-shot group. It's a little slow but that's to be expected with that powder. I wanted to get more eld-ms but couldn't find them so I went with the Bergers.

I think that's a very respectable velocity for the 6.5 Creedmoor.

 

[Bart B]

From a statistical point of view, it's my opinion that all those 3-shot test groups are equal in size. A 3X spread in group sizes across several 3-shot ones is normal. Shoot several 3-shot groups with the same load then note their sizes.

Their distance variation from point of aim may be due to slight shift of rifle hold and positions on its rests.

Great shooting anyway!!

 

[hunter67wa]

OCW is not about group size

 

[Bart B]

OCW is not about group size

What is OCW about if not group size? According to its developer, it is. All an optimal OCW has to do is shoot sub MOA.

Dan Newberry's OCW Load Development System

Dan Newberry OCW or Optimal Charge Weight Load Development method or system for handloading, reloading, bullets, brass, powder, primers, accurate handloads.

optimalchargeweight.embarqspace.com

 

[hunter67wa]

It is about where the rifle shoots the groups.

 

[new2mud]

To clarify the above, OCW is designed to find a forgiving node that will be resilient to slight powder charge variations and also temperature. And yes, it should yield a sub-MOA load that will be consistent across environmental changes.

However, it is all too easy to focus on group size when conducting OCW testing--which is why I remind folks that are doing OCW to focus on the group POI shift from group to group. This is why the 40.8-41.2 groups showed so much promise in the OP's original post.

Fine tuning seating depth around a 41.0 charge should result in a node that is very forgiving from day-to-day and temperature swings.

 

[Bart B]

If the POI shift across different charge weights is the objective, all charge weights must be shot from the same position using the same point of aim for each group. Reaimimg the rifle several inches away from the previously fired group will move the point of impact to a different place relative to the point of aim if the same load is fired again.

The rifle has to be fired exactly the same for each charge weight. No change of position across all charge weights.

 

[fremont]

41.8 and Goodnight, Irene. On to the next problem.......

 

[FURMAN]

Hi,
Unless I am not understanding what your pics indicate... it seems you are shooting 3 shots of one charge weight at each target. If that is the case, then you are missing the point of OCW. What you need to do is shoot one shot of each charge weight at all of the different targets... 6 charge weights would mean 6 holes in each target. One from each different charge weight and then determine which different powder loads cluster well together i.e. look for example if 41.6 and 42.0 hit at the same height on the target and generally in the same spot, then you may have found a node that would put the shots into the same spot on the target which is what you are looking for. This would allow you to use a load in that weight range that you could expect to consistently hit to the same spot. If you were off 0.1 or 0.2 grains in weight, it would not matter as that load should still hit to the same area on the target. That is what they mean by an accuracy node. A range of powder weight that generally hits to the same height and spread on the target.
Are ya with me on that?
Tens

This is incorrect