Reading OCW targets for 6.5 and .308

[Lefty Trigger]

Normally I shoot this OCW test and a ladder test at 300 but cant get on the 300 for awhile so looking for and outsider to view. The first test is 6.5 Creedmoor-24 inch with Reloader 15 / 140gr Nosler custom comp at .020 off the lands.
Second load is my 308-26inch with H4895 / 175gr Nosler custom comp at .030 off lands. The H4895 powder has a max of 42.7gr so I split the load and this is the lower half.

 

[Dusty Stevens]

36.4 on the first and 39 on the second plus a set of wind flags will fix you right up

 

[Lefty Trigger]

36.4 on the first and 39 on the second plus a set of wind flags will fix you right up

Thanks but can you tell me why on those choices? What do you see? I'm with you on the 36.5 because they are all real close on a horizonal plane. The 308 loads I figured the 40.2 load?

 

[jr600yd]

Smallest vertical spread

 

[JFrank]

I'm going to differ on both.
Your speed is a bit low on the 308 however 40.4 as is posted
There is a higher node for the Creedmoor

 

[Lefty Trigger]

I'm going to differ on both.
Your speed is a bit low on the 308 however 40.4 as is posted
There is a higher node for the Creedmoor

I have found with the 308 if I push the speeds too high the groups fall apart at distance, could be my bullet choice or any number of things. I was loading IMR4895 but decided to try a powder resistant to temp swings and no luck with Varget. First loads with the H4895 and getting decent 100yd groups, looks promising...
I agree with you on the Creedmoor as I thought that the higher loads were starting to come back together like if I went higher there would be another node. Some data books have 36gr as max for the RX-15 in the 6.5 Creedmoor.

 

[ckaberna]

Ease the CM up a little .... .2 or .3 at the time

 

[JFrank]

Hard to wrong at 40.2 for short range, an extra FPS would be handy at mid range

 

[Dusty Stevens]

Thanks but can you tell me why on those choices? What do you see? I'm with you on the 36.5 because they are all real close on a horizonal plane. The 308 loads I figured the 40.2 load?

I see missed conditions and very small dispersion besides that. Try those with varying seating depth over flags and youll be set

 

[L W P]

I have found with the 308 if I push the speeds too high the groups fall apart at distance, could be my bullet choice or any number of things. I was loading IMR4895 but decided to try a powder resistant to temp swings and no luck with Varget. First loads with the H4895 and getting decent 100yd groups, looks promising...
I agree with you on the Creedmoor as I thought that the higher loads were starting to come back together like if I went higher there would be another node. Some data books have 36gr as max for the RX-15 in the 6.5 Creedmoor.

Not sure about the RL-15 because I've never tried it. My node is more around 2810-2817 for my 140gr Hornady HPBT Match, but that's with Lapua SRP brass and CCI-450's. Pretty much all of my 140's (which ever brand) like to go faster than what your at now. Not saying that's a good thing, but you may try going higher in powder(SAFELY) to reach that node.

 

[Ned Ludd]

Lefty - perhaps you should read through the first few pages of Erik Cortina's Load Development at 100 Yds thread: http://forum.accurateshooter.com/threads/long-range-load-development-at-100-yards.3814361/. He explains very clearly and concisely how to conduct such an OCW test, and how to interpret the results. There are now over 100 pages in that thread if you want plenty of examples where Erik has analyzed posted groups and explained exactly why he picked a given charge weight region to test further.

The whole point of the OCW approach is to find at least two successive charge weight increments where the group center point does not move in relation to the point of aim. It has nothing at all to do with group size or vertical spread. By those criteria, consider re-testing the Creedmoor in 0.1 to 0.2 gr increments from 36.8 to 37.4 gr. For the .308, it's a little more difficult to decipher. It could be argued that 39.0 to 39.4 have about the same group center, but the same could possibly be said for 40.6 to 41.0 gr. Once you settle on a charge weight where the group center point doesn't change much for at least 0.1 to 0.2 gr to either side of the chosen charge weight, then you tune in group spread (size) via a seating depth test.

 

[Lefty Trigger]

Lefty - perhaps you should read through the first few pages of Erik Cortina's Load Development at 100 Yds thread: http://forum.accurateshooter.com/threads/long-range-load-development-at-100-yards.3814361/. He explains very clearly and concisely how to conduct suh an OCW test, and how to interpret the results. There are now over 100 pages in that thread if you want plenty of examples where Erik has analyzed posted groups and explained exactly why he picked a given charge weight region to test further.

The whole point of the OCW approach is to find at least two successive charge weight increments where the group center point does not move in relation to the point of aim. It has nothing at all to do with group size or vertical spread. By those criteria, consider re-testing the Creedmoor in 0.1 to 0.2 gr increments from 36.8 to 37.4 gr. For the .308, it's a little more difficult to decipher. It could be argued that 39.0 to 39.4 have about the same group center, but the same could possibly be said for 40.6 to 41.0 gr. Once you settle on a charge weight where the group center point doesn't change much for at least 0.1 to 0.2 gr to either side of the chosen charge weight, then you tune in group spread (size) via a seating depth test.

Thanks for that link and the explanation of what to look for.

 

[bill123]

Lefty - perhaps you should read through the first few pages of Erik Cortina's Load Development at 100 Yds thread: http://forum.accurateshooter.com/threads/long-range-load-development-at-100-yards.3814361/. He explains very clearly and concisely how to conduct suh an OCW test, and how to interpret the results. There are now over 100 pages in that thread if you want plenty of examples where Erik has analyzed posted groups and explained exactly why he picked a given charge weight region to test further.

The whole point of the OCW approach is to find at least two successive charge weight increments where the group center point does not move in relation to the point of aim. It has nothing at all to do with group size or vertical spread. By those criteria, consider re-testing the Creedmoor in 0.1 to 0.2 gr increments from 36.8 to 37.4 gr. For the .308, it's a little more difficult to decipher. It could be argued that 39.0 to 39.4 have about the same group center, but the same could possibly be said for 40.6 to 41.0 gr. Once you settle on a charge weight where the group center point doesn't change much for at least 0.1 to 0.2 gr to either side of the chosen charge weight, then you tune in group spread (size) via a seating depth test.

I came to the same conclusions. Lots of people seem to try OCW and then use a completely different criteria than Dan Newberry developed to read the targets. Some day when I have lots of time and a new barrel to waste, I'd really like to compare Eric Cortina's method, OCW, Ladder & muzzle velocity to see if they all align.

 

[!Peter!]

I'd really like to compare Eric Cortina's method, OCW, Ladder & muzzle velocity to see if they all align.

My testing shows that they don't.

 

[Ned Ludd]

Erik's method is very similar to Dan Newberry's OCW. I consider them the same from a practical/application viewpoint. Both take advantage of the change in POI (i.e. group center) due to differential barrel movement as charge weight increases. Finding successive charge increments where the group center doesn't move means you've found a region in the charge weight curve where barrel movement remains relatively consistent (i.e. relatively insensitive to changes in charge weight, and therefore velocity).

A ladder test is a different creature. Using single shots at each charge weight, you're looking for vertical spread on the target. Two or more successive charge weights that print holes on the target at the same (or very close) vertical position means you've found a charge weight region associated with positive compensation. Positive compensation simply means that slightly faster bullets leave the muzzle a tick earlier in the barrel harmonic cycle when the muzzle launch angle isn't quite as high, therefore their trajectory is slightly flatter. A bullet move slightly slower leaves the muzzle a tick later when the launch angle is higher. Although it is traveling with slightly less velocity, its trajectory has a higher arc, thereby allowing the slower bullet to hit the target at the same elevation as the slightly faster bullet. There are specific velocity/barrel time "windows" associated with this effect; those "window" or nodes are what you're looking for in a ladder test. I can readily understand why the two different types of testing methods may not give exactly the same results. However, I would expect at least a subset of the optimal charge weight regions to overlap, regardless of the type testing used.

 

[Twoboxer]

Ned gave a good explanation of Dan Newberry's OCW, and that many people say they are doing OCW but really aren't. Whether one believes in the method or not is irrelevant - if you are using OCW you are looking for common group center points.

Unfortunately I don't see any such pattern in the targets you posted. The pattern of group centers reminded me of times where I forgot to reset my parallax to the 100yd target. Decent group sizes, but inconsistent group centers.

Personally, I would have used 0.3gr increments at these charge weights, following Dan's early advice of 0.75% increments. But when I checked his current postings, he's recommending 0.7% to 1% now so maybe it's irrelevant. If the group centers shown are "real", it may have been easier to track the center's movement using 0.3gr increments.

 

[#40Fan]

Lefty, you are shooting small enough groups that you should be able to keep the dots close to each other and align them level with each other. Doing that will give you more to look at when you are doing this testing.

 

[Lefty Trigger]

Lefty, you are shooting small enough groups that you should be able to keep the dots close to each other and align them level with each other. Doing that will give you more to look at when you are doing this testing.

I would love to be able to do just that but sometimes I cant tell if it's me or the load causing the groups to spread out. I very seldom have a chance to get out beyond 300yds to practice and that is killing me but there is just no place to go close to me

 

[Lefty Trigger]

Lefty - perhaps you should read through the first few pages of Erik Cortina's Load Development at 100 Yds thread: http://forum.accurateshooter.com/threads/long-range-load-development-at-100-yards.3814361/. He explains very clearly and concisely how to conduct such an OCW test, and how to interpret the results. There are now over 100 pages in that thread if you want plenty of examples where Erik has analyzed posted groups and explained exactly why he picked a given charge weight region to test further.

The whole point of the OCW approach is to find at least two successive charge weight increments where the group center point does not move in relation to the point of aim. It has nothing at all to do with group size or vertical spread. By those criteria, consider re-testing the Creedmoor in 0.1 to 0.2 gr increments from 36.8 to 37.4 gr. For the .308, it's a little more difficult to decipher. It could be argued that 39.0 to 39.4 have about the same group center, but the same could possibly be said for 40.6 to 41.0 gr. Once you settle on a charge weight where the group center point doesn't change much for at least 0.1 to 0.2 gr to either side of the chosen charge weight, then you tune in group spread (size) via a seating depth test.

Taking your advice I'm making up loads for the 6.5 in 36.8, 37.0, 37.2, 37.4 and I'm going to retest again. Still unsure on where to go with the .308 though. I really believe that I shanked that bottom round on the 39.4 test as it seems kinda low for that load and how it grouped. The powder I'm trying has a ways to go before max at 42.7, actually Hodgdon has the starting load at 40.0 and Lyman starts at 37.0 I kinda guessed at a starting load of 39.0 as I really wanted my minimum velocity to be 2500. I'm thinking maybe doing a retest with the upper end and starting at 40.6 up to 42.0 and see how it does there.

 

[JFrank]

Normally I shoot this OCW test and a ladder test at 300 but cant get on the 300 for awhile so looking for and outsider to view. The first test is 6.5 Creedmoor-24 inch with Reloader 15 / 140gr Nosler custom comp at .020 off the lands.
Second load is my 308-26inch with H4895 / 175gr Nosler custom comp at .030 off lands. The H4895 powder has a max of 42.7gr so I split the load and this is the lower half.View attachment 1066620 View attachment 1066621

If I may say this about that,
You are close with the 308, although 175 Nosler isn't my favorite bullet they will shoot.
40.4 gr will put you right at 2600 FPS then tinker with seating.try .020
JMO