OCW or Velocity Node?

[Clucknmoan]

Seeking knowledge here as to which it really is, or is it both?

Say you are shooting an OCW and you come across a good flat spot in velocity and a consistent POI. If all the stars align, you should be able to load in the middle and shoot this and expect at least decent results. Of course there will be times it doesn't, but this is what we are after anyway. So then the next day or month for whatever reason your velocities have decreased by X amount and it's put you out of the flat spot you were in the day before. Weather, seating depth, whatever the reason, now it shoots like crap. Do you bump charge weight up to get back into that FPS where you saw the flats spot the day before? If so, why is it called an Optimal Charge Weight when it seems that it's really optimal velocity?

I guess another example would be seating depth. It seems like it's the chicken or the egg for which to find first, velocity node or seating depth. Say you run a ladder or velocity node test first and find a good flat spot, but you've got some horizontal and want to work on seating depth. Unless you are already close to the correct depth, as you make changes in depth there's not a chance you will still be in the same velocity flat spot you found closer to the lands at the same charge. So do you bump up a few 10th's to stay in that velocity flat spot as you seat deeper? This kind of leads me to believe that if you are looking to stay in a flat spot, it would be easier to start with seating depth than powder charge...or is that the chicken? If the charge weight you choose to do seating depths with happens to be on a scatter node, it's going to shoot like crap anyway.

From what I can comprehend about barrel harmonics (which isn't a lot Gentlemen!) it makes the most sense that tune is really dependent on the timing when the bullet exits the barrel. Am I on the right track here?

 

[Depart123]

Like many things, it depends.

If you are shooting at a paticular close distance say 100 or 200 yard benchrest or similar type shooting, then barrel timing can be an all important factor. If your bullets are exiting at the spot in a barrel's oscillation where it is the most consistent (which is at each end where it stops to change direction) then some velocity variation will be far less evident on the target. The barrel timing can be adjusted slightly by playing with seating depth.

In the long range game, especially at targets that might vary drastically in distance ( think PRS, or longe range hunting, or sniping) then a small standard deviation becomes a real factor. A load that might be a little less accurate at 100 or 200 yards but with a consistent single digit SD will show a heck of a lot less vertical dispertion as distances increase. These loads also can be tuned a bit as far as seating depth, but feed reliability has to be factored in as well.

In either case, the width of the node needs to be wide enough to accomodate temperature differences from winter to summer. If the load combo you are using provides a small enough node that it moves out of the good range, then I would consider that combo to be sub optimal. Some competitiors simply use the small nodes and adjust thier loads for current conditions. I don't have time or patience for that, especially considering variations from lot to lot in the powders themselves.

 

[Metal God]

The theory of the OCW is that you are in a rather large stable pressure curve zone resulting in consistent velocities and barrel time . If you find your true OCW , you should not have an inconsistent outing the next time out . That's the whole point of it . If you are having inconsistent results from trip to trip . You never actually were in your OCW zone . Dan compares the test to finding that sweet spot not unlike Fed GMM . That ammo seems to shoot well in any condition with any rifle . So if your results are all over the place you did not find your OCW as defined by it's inventor .

I've used Dan's method before with mixed results . Likely because I'm trying to read the results my self rather then the originator of the method . He offers individual personalized help if you want it . I will say I often read guys saying they did a OCW load development but changed the way they do it from Dan's actual instructions . Anything from changing the round counts , distance shot , different charge increments . Changing the method is fine but then expecting the final tweaking to be the same as the original method is not reasonable IMHO . If you tweaked the method you'll likely have to tweak how you come to the final load as well if you even can based on the changes and your ability to accurately read the groups .

How many times have you seen a guy post his OCW test groups and see the replies as to what's best be everything from start to finish in his progression ? Those threads tend to show most people don't actually know how to read the groups in the OCW method .

This was not to sound snarky or that I know better because I don't . It's just some observations I've noticed over the years that I thought were worth noting .

 

[CharlieNC]

Chuck why do you believe there is a velocity flatspot vs a target flatspot?

 

[gunsandgunsmithing]

Seeking knowledge here as to which it really is, or is it both?

Say you are shooting an OCW and you come across a good flat spot in velocity and a consistent POI. If all the stars align, you should be able to load in the middle and shoot this and expect at least decent results. Of course there will be times it doesn't, but this is what we are after anyway. So then the next day or month for whatever reason your velocities have decreased by X amount and it's put you out of the flat spot you were in the day before. Weather, seating depth, whatever the reason, now it shoots like crap. Do you bump charge weight up to get back into that FPS where you saw the flats spot the day before? If so, why is it called an Optimal Charge Weight when it seems that it's really optimal velocity?

I guess another example would be seating depth. It seems like it's the chicken or the egg for which to find first, velocity node or seating depth. Say you run a ladder or velocity node test first and find a good flat spot, but you've got some horizontal and want to work on seating depth. Unless you are already close to the correct depth, as you make changes in depth there's not a chance you will still be in the same velocity flat spot you found closer to the lands at the same charge. So do you bump up a few 10th's to stay in that velocity flat spot as you seat deeper? This kind of leads me to believe that if you are looking to stay in a flat spot, it would be easier to start with seating depth than powder charge...or is that the chicken? If the charge weight you choose to do seating depths with happens to be on a scatter node, it's going to shoot like crap anyway.

From what I can comprehend about barrel harmonics (which isn't a lot Gentlemen!) it makes the most sense that tune is really dependent on the timing when the bullet exits the barrel. Am I on the right track here?

Good post!

I do believe it's about velocity and harmonics...Timing of bullet exit and muzzle position. That's what tuners DO!

But, just like a tuner won't fix a bad bullet, they won't COMPLETELY fix velocity variation, either. They can have some effect by keeping the muzzle in a given position longer.

The example you gave is a good case for using a tuner. Just keep the velocity es minimal WITH a known good load.

IME, a good load is always a good load IF, you can affect the barrel and exit timing to keep up with atmospheric conditions.

 

[Clucknmoan]

Chuck why do you believe there is a velocity flatspot vs a target flatspot?

You mean why do I think there can be one without the other?

 

[Clucknmoan]

The theory of the OCW is that you are in a rather large stable pressure curve zone resulting in consistent velocities and barrel time . If you find your true OCW , you should not have an inconsistent outing the next time out . That's the whole point of it . If you are having inconsistent results from trip to trip . You never actually were in your OCW zone . Dan compares the test to finding that sweet spot not unlike Fed GMM . That ammo seems to shoot well in any condition with any rifle . So if your results are all over the place you did not find your OCW as defined by it's inventor .

I've used Dan's method before with mixed results . Likely because I'm trying to read the results my self rather then the originator of the method . He offers individual personalized help if you want it . I will say I often read guys saying they did a OCW load development but changed the way they do it from Dan's actual instructions . Anything from changing the round counts , distance shot , different charge increments . Changing the method is fine but then expecting the final tweaking to be the same as the original method is not reasonable IMHO . If you tweaked the method you'll likely have to tweak how you come to the final load as well if you even can based on the changes and your ability to accurately read the groups .

How many times have you seen a guy post his OCW test groups and see the replies as to what's best be everything from start to finish in his progression ? Those threads tend to show most people don't actually know how to read the groups in the OCW method .

This was not to sound snarky or that I know better because I don't . It's just some observations I've noticed over the years that I thought were worth noting .

Do you believe there is no relationship between OCW and velocity?

 

[Metal God]

It’s likey a direct correlation , what that does not mean is that a specific velocity means you found your optimum charge weight . Depending on the powder burn rate you could have the same velocity with 2 different powders with very different barrel times resulting in differet POI , so although velocity is important it’s not all that matters .

It’s likely why it’s harder to read/understand the OCW method then most think .

There’s also how you hold the rifle that will effect velocity and ES/SD . This is not as important when using heavy rifles or when shooting from a machine rest . How ever when shooting a rifle under lets say 13lbs or so held in hand fired using bipod or front and rear bag . How tightly or loosely you hold the rifle can effect velocity substantially.

My point to all this is there are so many factors to reading load development you can’t hang your hat on any one thing and is why poi , group size and velocity all matter when reading your OCW .

All my over all point was is that if your load is inconsistent from range trip to range trip . You have not likely found your OCW regardless of what your velocities are .

 

[Clucknmoan]

It’s likey a direct correlation , what that does not mean is that a specific velocity means you found your optimum charge weight . Depending on the powder burn rate you could have the same velocity with 2 different powders with very different barrel times resulting in differet POI , so although velocity is important it’s not all that matters .

It’s likely why it’s harder to read/understand the OCW method then most think .

There’s also how you hold the rifle that will effect velocity and ES/SD . This is not as important when using heavy rifles or when shooting from a machine rest . How ever when shooting a rifle under lets say 13lbs or so held in hand fired using bipod or front and rear bag . How tightly or loosely you hold the rifle can effect velocity substantially.

My point to all this is there are so many factors to reading load development you can’t hang your hat on any one thing and is why poi , group size and velocity all matter when reading your OCW .

All my over all point was is that if your load is inconsistent from range trip to range trip . You have not likely found your OCW regardless of what your velocities are .

I'm not referring to a specific range trip or even specifically from day to day. The change in velocity could be from summer to winter or changing from .005 off to .050 off.

Seating depth is the easiest factor to use as an example. Say you indeed found your OCW at 49.0 grains and it happened to be at a velocity of 3000. Next you move to seating depth and find that the group actually starts improving as you seat deaper. Say you've adjusted .030 and it's continually gotten better, but you velocity has dropped to 2960 because you are seating deeper. Do you bump charge up to get back to that 3000 fps and continue in seating depth increments?

 

[seymour fish]

Do you believe there is no relationship between OCW and velocity?

There seems to be a deconstructionist take on Creighton Audette’s work, in which one part or another is taken to be the Essence, given a buzzword, and rolled out, to an absurd conclusion

 

[Clucknmoan]

There seems to be a deconstructionist take on Creighton Audette’s work, in which one part or another is taken to be the Essence, given a buzzword, and rolled out, to an absurd conclusion

There seems to be a deconstructionist take on Creighton Audette’s work, in which one part or another is taken to be the Essence, given a buzzword, and rolled out, to an absurd conclusion

Why don't you clarify what you are getting at. This way an actual question, because I really am interested in what he has to say.

 

[Depart123]

Dan's OCW method attempts to combine several factors into a single operation. It is at it's best when done at a distance that will make velocity variations (vertical stringing) apparent. In my opinion, (and it is just my opinion), people try to do the OCW thing at 100 yds and variations between groups are just too small to read easily.

 

[seymour fish]

Why don't you clarify what you are getting at. This way an actual question, because I really am interested in what he has to say.

Cluck, Audettes method centered on first having your shooting technique squared away, then loading powder at evenly spaced increments appropriate for case cap, starting well below any Max, and fired using One Round of each successive charge, at same POA at fixed yardage, recording POI of each successive shot, to find a cluster on the vertical axis of perhaps 4 shots. He plotted shot placement on graph paper and found some occasional correlation between clusters (nodes) and plateau in MV, but didn’t seem to hang his hat on it. The spread of powder charges giving same vertical gives insight as to your powder choice. Whole thing including Foulers can be accomplished in 10-15 rounds. Saves precious time. Load to the center of your node, run a couple thru some chrono, plug data into ballistic app, take it straight to 1000. You could OCW till the cows come home and the bbl is toast before getting there, or even figuring out your powder choice was suboptimal. You could fire successive charge increases across a chrono, not bothering with a target, and hope the velocity plateau bidness is Money, but Why ? I think it best to take the whole of what he said. Precision Shooting roughly mid-90’s ran it. Best of luck and Happy NewYear, seymour

 

[Clucknmoan]

Cluck, Audettes method centered on first having your shooting technique squared away, then loading powder at evenly spaced increments appropriate for case cap, starting well below any Max, and fired using One Round of each successive charge, at same POA at fixed yardage, recording POI of each successive shot, to find a cluster on the vertical axis of perhaps 4 shots. He plotted shot placement on graph paper and found some occasional correlation between clusters (nodes) and plateau in MV, but didn’t seem to hang his hat on it. The spread of powder charges giving same vertical gives insight as to your powder choice. Whole thing including Foulers can be accomplished in 10-15 rounds. Saves precious time. Load to the center of your node, run a couple thru some chrono, plug data into ballistic app, take it straight to 1000. You could OCW till the cows come home and the bbl is toast before getting there, or even figuring out your powder choice was suboptimal. You could fire successive charge increases across a chrono, not bothering with a target, and hope the velocity plateau bidness is Money, but Why ? I think it best to take the whole of what he said. Precision Shooting roughly mid-90’s ran it. Best of luck and Happy NewYear, seymour

Appreciated. I understand Audettes method, it by far makes the most sense to me. I get that he didn't hang his hat on velocity but rather POI, but they do seem to coincide. So my question would still hold true for a ladder as it would for an OCW. You find flat spot at distance shooting a ladder, velocity and ES is stable. You change seating depth to tighten up horizontal but your velocity will no doubt change when doing so. Do you find that it helps to bump charge up to get back in that velocity sweet spot? I understand the real answer is do what the paper tells you, just trying to see what everyone has seen for tendencies.

 

[Metal God]

Seating depth is the easiest factor to use as an example. Say you indeed found your OCW at 49.0 grains and it happened to be at a velocity of 3000. Next you move to seating depth and find that the group actually starts improving as you seat deaper. Say you've adjusted .030 and it's continually gotten better, but you velocity has dropped to 2960 because you are seating deeper. Do you bump charge up to get back to that 3000 fps and continue in seating depth increments?

Yes I'd give it a try but would not count on getting the same groups . I'd also look at your POI first and be sure that has not moved from where you found your OCW . If your POI has moved then your likely heading away from that node .

I did not see what you are loading but 40fps is likely .4 to .6gr difference in the 30cal cartridges unless you're talking 300wm . The OCW theory is to give you a large sweet spot to work with as far as charge weight . So if you did find that node but seating deeper started dropping you out of it . .4gr more may very well put you right back in that sweet spot .

 

[seymour fish]

Appreciated. I understand Audettes method, it by far makes the most sense to me. I get that he didn't hang his hat on velocity but rather POI, but they do seem to coincide. So my question would still hold true for a ladder as it would for an OCW. You find flat spot at distance shooting a ladder, velocity and ES is stable. You change seating depth to tighten up horizontal but your velocity will no doubt change when doing so. Do you find that it helps to bump charge up to get back in that velocity sweet spot? I understand the real answer is do what the paper tells you, just trying to see what everyone has seen for tendencies.

Cluck, now you’ve done it. Lmao ! I am in the Positive Compensation camp at long range. Have regularly seen loads with ES in the teens shoot way inside what a linear thought process based on MV-related dispersion would insist on as impossible. Minor seating depth changes make velocity changes which won’t move you off your pos comp node, unless you were on the ragged edge of it. Once you get seating depth set, try very fine powder tuning at your distance, say 0.1 gr increments/3-5 shot groups. You want a stable crosswind. Look for wind sensitivity. Above is legit given a system which produces positive compensation. Many don’t, and seem much more reliant on super tight ES. Seymour

 

[Metal God]

Minor seating depth changes make velocity changes which won’t move you off your pos comp node, unless you were on the ragged edge of it. Once you get seating depth set, try very fine powder tuning at your distance, say 0.1 gr increments/3-5 shot groups.

That's the thing I've never understood . If the OCW method is to be believed , that would mean if you're in your "OCW node" , .1gr should have virtually zero effect on anything and has always been where my confusion lies with this method . You your self just said you've seen ES in the teens that shoot great so what is .1gr or 3 Kernels of IMR-4064 really going to change ?

 

[Clucknmoan]

Yes I'd give it a try but would not count on getting the same groups . I'd also look at your POI first and be sure that has not moved from where you found your OCW . If your POI has moved then your likely heading away from that node .

I did not see what you are loading but 40fps is likely .4 to .6gr difference in the 30cal cartridges unless you're talking 300wm . The OCW theory is to give you a large sweet spot to work with as far as charge weight . So if you did find that node but seating deeper started dropping you out of it . .4gr more may very well put you right back in that sweet spot .

This is exactly what I don't understand about the OCW. If you find an OCW, then have to bump up a few .010's to stay in that node due to variables as described above...isn't it more of a Optimal Velocity instead of Optimal Charge Weight?

 

[saintsfan1977]

That's the thing I've never understood . If the OCW method is to be believed , that would mean if you're in your "OCW node" , .1gr should have virtually zero effect on anything and has always been where my confusion lies with this method . You your self just said you've seen ES in the teens that shoot great so what is .1gr or 3 Kernels of IMR-4064 really going to change ?

MG,
Dan says to load 0.1gr above and below your ocw so you can find how wide the node is. That way in the summer you use the lower powder charge and in the winter, the higher powder charge. I'm a noob but that's what I read from his site.

 

[Metal God]

I believe he only recommends percentages rather then grains . This is because the more powder a cartridge holds the less .1grain effects it . Meaning generally speaking 223 = .25gr , 308 = .4gr , 30-06=.5gr , 300win mag = .6gr etc etc . Example and this is really the extremes on this but .1gr will effect a 9mm much more the it would a 50BMG . In the case of the latter you can work up in 2+ grain increments


From Dans website
http://optimalchargeweight.embarqspace.com/ocw-instructions/4529817134
(
4. Back away from the maximum charge by 7 to 10 percent, and load one test round with this charge. Add 2% to the charge weight, and load another cartridge with that charge. Load a third test cartridge with the next 2% graduation. You will use these three cartridges for sighters, and more importantly to determine pressure tolerance in your individual rifle.

5. Add another 2% or so to the charge level used in cartridge #3 of step 4, and load three rounds with this charge weight. Add .7% to 1% to this charge, and load three more. Add that same graduation again, and load three more. Continue adding the chosen graduation until you have moved ONE increment above your chosen maximum powder charge. )

From Dans website (18. Your next step would be to confirm your load recipe at the maximum range you will expect to use it. Load one round about 1% below, and another round about 1% above the OCW charge, and fire a three shot group with these two charges plus the standard charge at the maximum range you will require the load to be accurate at. You should note MOA, or very close to MOA grouping...)