OCW Testing - Vertical Stringing

[Allen One1]

Ran an OCW test today on some powder charges that I had determined might be productive, 3 of the groups look good dropping in directly under the point of aim. What I thought was odd is that they all ran a fairly vertical string, all holes touching and the string running about 3/8 inch.

Things that I suspect could cause this are, shooter and/or new brass rather than once fired. It was cool 40 degrees with about 8 mph wind right to left. Shooting at 100 yards.

6.5 Creedmoor, Starline brass, 140 gr ELD-M, CCI 400 primer, H4350

 

[JFrank]

Lots of things can cause vertical stringing
Can you please post a photo of your target

 

[Allen One1]

Lots of things can cause vertical stringing
Can you please post a photo of your target

3 Shot groups

 

[Allen One1]

A couple of related 5 shot groups shot today as well.

 

[Varminterror]

100yrd groups, vertical stringing isn’t velocity spread, it’s shooter induced or barrel asking for more powder.

What are the velocities for the respective groups of the ladder?

 

[Allen One1]

42.0 - 2692
42.2 - 2716
42.4 - 2726
42.6 - 2735
42.8 & 43.0 are not available since I threw them in at the last minute for the OCW. Mistake on my part.

 

[Allen One1]

100yrd groups, vertical stringing isn’t velocity spread, it’s shooter induced or barrel asking for more powder.

What are the velocities for the respective groups of the ladder?

Barrel asking for more powder is interesting.

 

[Varminterror]

Doesn’t really appear like there’s a velocity node in there.

 

[JFrank]

I’d go with mechanical
5 outta 6 are vertical with different charges’ what’s the common denominator? Set up or shooter

 

[JFrank]

A couple of related 5 shot groups shot today as well.View attachment 887214

Those look good

 

[lordpaxman]

Doesn’t really appear like there’s a velocity node in there.

I’m just getting started with OCW and this workup is interesting. Where does the OP go from here? When I look at the 3 shot groups it doesn’t look like there’s a lot of vertical movement in the centers. 42.8 and 43 looked like there was a potential node there but with no velocity data it’s difficult to tell.

 

[JFrank]

I’m no damn good at those OCW test
I’ll take a single shot ladder any day.
Anyway vvv
We were discussing the vertical shape of the group, at least I was..
j

 

[JFrank]

100yrd groups, vertical stringing isn’t velocity spread, it’s shooter induced or barrel asking for more powder.

What are the velocities for the respective groups of the ladder?

Ive seen vertical indicate a break out (overcharging) many times

 

[Allen One1]

I’m just getting started with OCW and this workup is interesting. Where does the OP go from here? When I look at the 3 shot groups it doesn’t look like there’s a lot of vertical movement in the centers. 42.8 and 43 looked like there was a potential node there but with no velocity data it’s difficult to tell.

Where to go from here is the question. I think I load additional rounds at 42.8 & 43.0 and then load a couple of higher charges at 43.2 and 43.4 and shoot another OCW along with velocity on all of them. So far I have no pressure signs. I keep waiting for it to fall apart at some point but this barrel doesn't appear to be too picky about anything.

 

[JFrank]

@Allen One1
Finding a node should be relatively easy as pictured below.

 

[Varminterror]

OCW and Ladder tests can’t be shot at 100 yards with meaningful results. Satterlee Velocity curves can be fired at 100 yards, or fired without a target at all, really. Newberry OCW and Audette Ladders really need to be fired at 300 yards, better at 600-1000 yards, to really establish meaningful results.

 

[lordpaxman]

OCW and Ladder tests can’t be shot at 100 yards with meaningful results.

I was following the instructions from Newberry, which has you place targets at 100yards. The concept as I understand it is to plot POI across the various loads. I got a Labradar so I could also get velocity measurements while doing this to see if there was some correlation with velocity nodes but that’s secondary to the charge weight idea and not in Newberry’s process.

 

[forrest r]

I'd check the torques on the action screws just for the heck of it. Too loose and you get horizontal stringing. Too tight and you get vertical stringing.

Another thing to test is pieces of a wide rubber band at the forend of the stock. Put enough there to put upward pressure on the bbl. Do your standard testing with the upward pressure on the bbl. Then do the same testing without anything in the stock. Compare the targets, if the groups are rounder/tighter with the upward pressure on the bbl. That's telling you it's a bedding issue.

 

[Varminterror]

I was following the instructions from Newberry, which has you place targets at 100yards.

The advice is free, but I’ll tell you, I made the mistake 20yrs you’re making right now by trying to shoot these tests at short ranges. It’s asking for headaches. There’s far too much vulnerability to false results when shooting these at short ranges. These tests really need to be moved out to at least 300, better 600-1000 to be able to truly observe the inherent vertical, allowing the distance to exceed mechanical/shooter issues. You’ll note in the target @South Prairie Jim posted above, he fired a ladder (same fundamental principles as OCW, just different CoF) at 300 and still ended up with a tiny little cluster. It’s distinct enough to make some observations, but even more range would make the results more obvious. Gotta consider here - his target is at 300, I’m mentioning 300+, that’s two folks here which are NOT new to these development tests who are showing you a better way - take the advice.

At short ranges, you’ll see disparity between OCW, Ladders, and Satterlee tests (velocity curves) - these are induced experimental errors, not a true disagreement of results. At longer ranges, you won’t see this disagreement between methods - at longer ranges, you’ll get the same result no matter whether you follow to the letter Satterlee, Newberry, or Audette.

 

[JFrank]

@Varminterror
I don’t know those three fellas but I do know how confirm a node. I’m not even sure if it’s a better way but it works for me.
Addendum- # 5 is a great example of breaking out the top ( overcharged and went vertical)
J

 

[Varminterror]

@South Prairie Jim - you might not have heard the name before, but you’re shooting the Creighton Audette Ladder test.

For the OP and others: There are lots of different ideas out there to reach small groups at long ranges, but there seem to only be 3 known and proven common methods which are repeatable. The Audette Ladder is one of them. Dan Newberry’s OCW test does the same thing (comparing vertical dispersion at range), but fired at multiple POA’s instead of one (which some argue introduces more mechanical error than the Audette test). The Scott Satterlee test is different than the other two in that it doesn’t even need a target, and only uses velocity difference between adjacent charge weights, which we know will present as vertical dispersion at range. Most guys I know don’t exclusively shoot the Satterlee test, since it feels unnatural to shoot rounds at nothing, so we typically confirm the velocity curve with Audette Ladder or Newberry OCW with the same rounds. At 100 yards, it’s common for mechanical/shooter issues to yield disagreement between these two concurrent tests - the velocity nodes may not align with the POI vertical nodes. By firing at 600-1000, I have not observed any disagreement. The velocity nodes line up with the POI nodes. So I’ve leaned to never put much belief into 100 yard Ladder or OCW tests.

 

[JFrank]

I’ve heard of them, I just don’t know them.
Eric Cortina has a 100 yard load development thread on AS that expanded onto 100 pages mostly people finding fault and arguing like little kids. I don’t know him either...
I’ve pretty much stopped trying to influence anyone rather test a bit and post results and if someone finds value then I’m good, if not that’s fine also.
J

 

[JFrank]

There’s also color affinity, I believe it’s called.

 

[lordpaxman]

The advice is free, but I’ll tell you, I made the mistake 20yrs you’re making right now by trying to shoot these tests at short ranges.

I appreciate the advice! My backyard goes to 400yds, I'll see what I can do. Thanks.

 

[JFrank]

@Varminterror
You may be more familiar with the Tony Boyer method of tuning where multiple charges with multiple seating depths all shot at a large target board using multiple bullseye’s .
Hopefully I haven’t butchered that too much.
LOL but a few short range fellas are quite versed showing excellent results.
J