OCW or Velocity Node?

[seymour fish]

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?

Or is it optimum barrel time?

 

[Metal God]

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?

If I were to give it a definition that better describes what it really is . I'd call it OBT ( optimal barrel time ) but there is also the point in which the pressure stabilizes for lack of a better term and even though your charge weights are going up in those consistent increments your velocities actual level off in some areas . So lets say your loading in .5gr increments which I used to do for 308 . When I used powders in the burn rate area of IMR-4064 & 4895 my velocities went up pretty consistently 40fps for every .5gr of powder added . The OCW is "supposed" to find that spot were that consistent 40fps graduation slows to half that or less .

Keeping in mind these are just general made up numbers
Meaning instead of your powder charge from 44gr to 45gr jumping 80fps it only jumps 40fps or less . This is your so called velocity node or OCW because you now have found a stable zone with in charges 44gr & 45gr that small variances should not effect it's over all performance . Your pressure not only stabilizes/equalizes resulting in smaller ES between those charges . Your barrel time stabilizes as well and should be more consistent

Now that all said . I want to be clear on this . All that above is , is "my" understanding of the "theory" of the OCW method . I've been wrong before ;-)

 

[hunter686]

I have used the OCW method and have done well by it but found everthing had to be right in order to get the correct results from this method. With my latest build i decided to go for a velocity plateau. I load up 1 single round at .2 grains increments and find out where I have the least deviation. For me I have a node at 2900 that doesn't more than 20fps over .8 of a grain of powder. I can honestly say the load I have in my rifle was found after 10 rounds - didnt touch seating - and havn't touched it 500 rounds in. I have taken a couple 1000 yard matches with this rifle with this load. This gives me under a half minute at 1k and 1/4 to 3/8 vertical at 315 yards in field conditions.

When you find the RIGHT load for your rifle the rest of it becomes idiot proof. Especially when it comes to your loading technique. When I hear guys cutting grains of powder in half that just tells me they don't have it.

 

[ShootDots]

Here is an observation I have noticed that has played out true time after time with 1 distinct exception. I have shot enough different cartridges over time to "learn them". I have shot enough bullets to "generally" know where they like to be in many, if not most, rifles. So I start out near a charge weight that has proven itself to ME on a regular basis. EXAMPLE #1: in most of my .260A.I.'s they LOVE H4350 powder. With L/R Primer brass, almost invariably 43.2-43.5 using the Berger 140gr. LRBT bullet seated 7K INTO the lands. So I will start at 42.7grs and work in 0.2gr increments UP to 43.5grs with CCI BR-2 primers. Seven (7) out of Ten (10) times it will land right at 43.3gr with no other changes. But if it is NOT doing what you want, ONLY CHANGE ONE (1) COMPONENT AT A TIME to figure out where the "problem" is. Since I have decided to start using RL-16, and knowing it is virtually on top of H4350 in burn rate, I merely substitute RL-16 in place of H4350 and use FED 210primers (which RL-16 and 23 seem to have an affinity for) and run the same load development ladder test. VOILA! At 43.2 and 43.4grs, the groups were almost identical. So I "split the difference" at 43.3grs and went and did a seating depth test at 300 yards. At 7K INTO the lands and 5K OFF the lands the groups produced 1/2" and 5/8" respectively. The 7K into the lands had a NICE "looking" group where the other was somewhat stringing a tad vertical. So I chose the 7K into the lands and went and shot a 1000 yard match. It exceeded my expectations!
NOW EXAMPLE#2: I have tried enough 7mms, I.E. from a 7mm-08A.I. thru "Straight" .284s to Shehanes and a couple of 7 SAUMS. Most people shoot their "non-magnum" 7s in the 2775-2840f.p.s. range. If you notice on the OBT (QL Barrel Time) they are at an "in between" "node". However, many 7mm barrels WILL shoot there. BUT T-Rust me, there are "more than a few" that will not! With those barrels, if you are not in the correct OBT node, they will not shoot! It tis a good thing that many will shoot decently in that "in between node"!

I have said all this to say that BOTH can be valid! But let me give you EXAMPLE #3: I do not use QL BUT a couple of my friends are QL "gurus". They help me along whenever I ask them. When I have, it has been my experience, with the 6.5s, that BOTH the OCW and the OBT are EXACTLY the same! I believe that that is the REASON why the 6.5s are so easily tuned and VERY, VERY accurate. EXAMPLE #2: above is precisely what I am stating here.

I hope this helps and does not muddy the waters for you!

 

[Depart123]

I guess I do it back asswards from everyone else. I use a chronograph to find a range that gives me small SD's as well as acceptible velocities with some head room left at the top. Then I go back and shoot that range again with a minimum of ten rounds per group to get a true picture of my dispertion and the shape of my group.

Since I have already found the optimal charge range for velocity consistency, then any vertical seen in the groups can be attributed to the barrel movement in it's oscillation pattern. If 2 or 3 of those groups show themselves to be round, and to the same POI, then that is where I want to be.

Only then do I play with seating depth to see if I can tighten it any.

Of course, we only agonize over this stuff because most of us don't have the ability to test loads at extended ranges to begin with. If you are able to shoot groups at say 600 yards to begin with, then all of this is largely unnecessary. I would say that anything that groups at those ranges can automatically be considered good.

 

[CharlieNC]

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

A number of intetesting takes have been proposed to explain barrel harmonics as the causation of a node (OBT, compensation, and timing the bullet exit at the top or bottom of a cycle). Load development seeks to find a charge to provide the proper timing, while tuners seek to alter the harmonics to suit the timing. None of these mechanisms infer velocity plateaus are involved.

More recently there are proposals to skip the target altogether and with a shot or two, find a velocity plateau via charge weight. Ignoring the statistics of limited shots don't support this, I have difficulty understanding the physics explaining how this can occur. I'm open minded to the concept but have never seen any convincing evidence.

 

[Clucknmoan]

Or is it optimum barrel time?

If I were to give it a definition that better describes what it really is . I'd call it OBT ( optimal barrel time ) but there is also the point in which the pressure stabilizes for lack of a better term and even though your charge weights are going up in those consistent increments your velocities actual level off in some areas . So lets say your loading in .5gr increments which I used to do for 308 . When I used powders in the burn rate area of IMR-4064 & 4895 my velocities went up pretty consistently 40fps for every .5gr of powder added . The OCW is "supposed" to find that spot were that consistent 40fps graduation slows to half that or less .

Keeping in mind these are just general made up numbers
Meaning instead of your powder charge from 44gr to 45gr jumping 80fps it only jumps 40fps or less . This is your so called velocity node or OCW because you now have found a stable zone with in charges 44gr & 45gr that small variances should not effect it's over all performance . Your pressure not only stabilizes/equalizes resulting in smaller ES between those charges . Your barrel time stabilizes as well and should be more consistent

Now that all said . I want to be clear on this . All that above is , is "my" understanding of the "theory" of the OCW method . I've been wrong before ;-)

This makes more sense to me. OBT may be a better way to describe what I'm getting at.

 

[Depart123]

A number of intetesting takes have been proposed to explain barrel harmonics as the causation of a node (OBT, compensation, and timing the bullet exit at the top or bottom of a cycle). Load development seeks to find a charge to provide the proper timing, while tuners seek to alter the harmonics to suit the timing. None of these mechanisms infer velocity plateaus are involved.

More recently there are proposals to skip the target altogether and with a shot or two, find a velocity plateau via charge weight. Ignoring the statistics of limited shots don't support this, I have difficulty understanding the physics explaining how this can occur. I'm open minded to the concept but have never seen any convincing evidence.

To my mind, a good node is the convergence of a good velocity node and harmonic node. I'm in your camp as far as I fail to understand how single shots can tell you anything, except maybe the very general velocity window you are in.

 

[Clucknmoan]

I guess I do it back asswards from everyone else. I use a chronograph to find a range that gives me small SD's as well as acceptible velocities with some head room left at the top. Then I go back and shoot that range again with a minimum of ten rounds per group to get a true picture of my dispertion and the shape of my group.

Since I have already found the optimal charge range for velocity consistency, then any vertical seen in the groups can be attributed to the barrel movement in it's oscillation pattern. If 2 or 3 of those groups show themselves to be round, and to the same POI, then that is where I want to be.

Only then do I play with seating depth to see if I can tighten it any.

Of course, we only agonize over this stuff because most of us don't have the ability to test loads at extended ranges to begin with. If you are able to shoot groups at say 600 yards to begin with, then all of this is largely unnecessary. I would say that anything that groups at those ranges can automatically be considered good.

This is exactly what I do to work loads usually.

I am lucky enough to be able to shoot right from the loading room. I would rather just shoot ladders, but that's difficult at the house. I have back stops at 133 and 250 yards, which are really easy to get to and change paper on, but those aren't far enough to shoot a good ladder. I do have gongs at 450, 800 and 900, but it's not feasible to change paper on them, not unless I get a Sherpa.

This is why I have been trying to get the OCW method ironed out and working, but me and the OCW don't see eye to eye.

 

[hunter686]

A number of intetesting takes have been proposed to explain barrel harmonics as the causation of a node (OBT, compensation, and timing the bullet exit at the top or bottom of a cycle). Load development seeks to find a charge to provide the proper timing, while tuners seek to alter the harmonics to suit the timing. None of these mechanisms infer velocity plateaus are involved.

More recently there are proposals to skip the target altogether and with a shot or two, find a velocity plateau via charge weight. Ignoring the statistics of limited shots don't support this, I have difficulty understanding the physics explaining how this can occur. I'm open minded to the concept but have never seen any convincing evidence.

My take on the velocity the plateau is that if your rifle likes a velocity then provided you don't go outside that "node" there shouldn't be any deviation in impact other than atmospheric conditions. I'm fortunate being based in Scotland we don't have the same temp swings you guys have say in Texas. I never bothered with groups when testing the velocities i purely went on the flat spot. and stuck with it. I have attached the notes i took when shooting the groups to give you an idea on how i worked out. I ended up on 45.5. Not saying this a fail safe method but it makes sense to me and the target seems to like it. If the group wasn't to my liking after selecting the powder charge then i would mess with the seating depth. I don't claim to be a guru on this just giving you my experience with this method.

I was bit annoyed though. Finding a load for a rifle is one of my favourite things and this took all the fun out it

p.s this isn't a bench gun. That group was shot off a bipod in the prone

 

[C.E.Smith043]

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 .

Spot On!!!!!

 

[Depart123]

The main issue I have with the Dan's method, is that it assumes that optimal pressure resulting in coinciding POI at a given distance (200 yards and closer) is indicative of small SD's and good long range performance with respect to vertical dispersion. That may well be true in many cases, but I have found it to be misleading enough times not to trust it exclusively.

 

[seymour fish]

A number of intetesting takes have been proposed to explain barrel harmonics as the causation of a node (OBT, compensation, and timing the bullet exit at the top or bottom of a cycle). Load development seeks to find a charge to provide the proper timing, while tuners seek to alter the harmonics to suit the timing. None of these mechanisms infer velocity plateaus are involved.

More recently there are proposals to skip the target altogether and with a shot or two, find a velocity plateau via charge weight. Ignoring the statistics of limited shots don't support this, I have difficulty understanding the physics explaining how this can occur. I'm open minded to the concept but have never seen any convincing evidence.

Charlie, have seen velocity flatten, with 100 yard groups in the low ones, simply from “running out of primer”. Same load at 600=10” vertical. Velocity 200 FPS below desired. Hotter primer produced stepwise increase in vel per incremental powder charge increase all the way up to “pressure”, yet the ladder showed a node across 1-1/2 gr. Center of that node held “minute of black and white TV” to 1600, 0.4 MOA at 1K, but never better than 3/4 inch at 100. Quickload modeling gave barrel time 1% longer than original formula for bbl length, which is often the sweet spot for my good loads. Seems what happens on target encompasses the whole of the thing. Answers more questions than have been posed