OCW Interpretation please.

[Lonewolf74]

I am using the pro chrono. Usually is decently consistent but I was shooting through it at all different angles and don't think it liked it.

I am using Remington brass. I haven't started neck turning yet. I did sort bullets by weight and brass by weight but am planning on actually sorting brass by case volume. I did use a RCBS Chargemaster to throw charges.

I have the charge master setup too and it will vary +- 2/10ths between charges. I use a beam scale and trickler to verify each charge and this has helped my ES quite a bit. I would recommend going the same route before getting into neck turning. It's all good practice in the pursuit of consistent reloads but I think verifying your charges will give you bigger returns.

 

[BountyHunter]

Ok there is no way in hell to get an accurate long range load with that extreme spread no matter what technique you are using. You need to figure out what the ES issue is first, otherwise you are just wasting bullets and barrel.

 

[jasonco]

73.9 looks good to me, but those optical based chrono's can give you fits, with the ES/SD, from what I'm seeing.

 

[howlemup]

Thanks for all the help guys. I think I am going to play with the 73.6 area. I'll check back in once I have played around with this load range.

75.1 started showing pressure signs.

 

[Alex Wheeler]

Did you see pressure signs? Looked like it was about to get good.

 

[Mike 338]

73.6 to 74.5 all center in the same place. 73.9 falls in the middle of those and shoots great. Done.

 

[Alex Wheeler]

As distance increases node width decreases. There is no such thing as a wide node at 1000 yards. Just be sure you take it out to long range and verify your groupings.

 

[Greyfox]

IMO, to get a more viable OCW I would do a couple of things. First, it's apparent that there is something screwy going on with Your chronograph, quite typical of many optical units. I would recommend getting your hands on a Magneto-speed, and measure velocity independent of your POI as the MS can effect accuracy due to barrel contact. . I believe velocity is important when running an OCW since you can see sweet spots in the velocity change per unit charge of powder. Lower is better. I find 100 yards is too close for a decent OCW test, 200 or 300 yards provides more meaningful info. You are focusing more on elevation differences then horizontal. Based on your 100 yard data, I would be inclined to build my ladder around the 75Gr charge in .3 gr. Increments given you are not experiencing pressure signs. You didn't mention your powder, but if you are using a burn rate in the H4831-H1000 or Retumbo range you should be in the 75Gr range for optimum velocity/case capacity. What you are looking for is the weight range that has the least change in elevation POI and lowest change in FPS per .1gr of powder charge. Once you find this sweet spot, you can work on optimizing seating depth, etc.
This is a recent OCW that I ran to check out a lot change in powder and bullets with my 6.5x47 used for PRS competition. My sweet spot was 41,2gr. It fortunately turned out to be identical to my prior lots.

 

[FURMAN]

OCW is best done at 100 yards and the picture you posted is not an OCW. Ladders, in my opinion, are far more valuable and best performed as far as you can shoot out to 1000 yards. With the OCW you are ONLY looking for the widest node you can find as far as point of impact, NOT vertical and should be followed up with velocity checks if not done at the same time as the OCW. The "node" with two or three identical points of impact(over as many powder charges) will almost always have a low es and sd in velocity. Ladders are mostly focused on vertical but as Alex has pointed out in his threads about the ladder big horizontal with no wind is usually caused by incorrect seating depth. Pick a load development method and stick with it. I think it is easiest for knew shooters to perform the OCW especially since many do not have access to the ranges required for best ladder results.