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ocw test method

cjmac

Silver $$ Contributor
So its been a long year , IV been everywhere on this earth with work .. So with my 223, 1 in 7 twist Im wanting to try imr 4166 and n140 with 77 gr SMK. From what I understand from Dan Newberry ocw methods are . With different charges at different targets fire groups allow time to cool between shots

. Seating depth at this point is not critical but make the same length. It can be tuned later . ( would I be better off to start at mag length OR just off the lands ? )

Look at the groups , you want the groups that are consistent in same position on the target lets just say 3 groups 19.0 , 19.2 , 19.4 landed at 12 o'clock , and 2 groups landed at 9 o'clock

At this point I would want to test 19.2 again ? Maby shoot 5 more groups and see if that land at 12 o'clock again ? That would be a good load ?

Then start adjusting my seating depth ..
 
So its been a long year , IV been everywhere on this earth with work .. So with my 223, 1 in 7 twist Im wanting to try imr 4166 and n140 with 77 gr SMK. From what I understand from Dan Newberry ocw methods are . With different charges at different targets fire groups allow time to cool between shots

. Seating depth at this point is not critical but make the same length. It can be tuned later . ( would I be better off to start at mag length OR just off the lands ? )

Look at the groups , you want the groups that are consistent in same position on the target lets just say 3 groups 19.0 , 19.2 , 19.4 landed at 12 o'clock , and 2 groups landed at 9 o'clock

At this point I would want to test 19.2 again ? Maby shoot 5 more groups and see if that land at 12 o'clock again ? That would be a good load ?

Then start adjusting my seating depth ..

That sounds about right for the OCW method! Is this a hunting, benchrest or fclass rifle?

Another option is 3 round groups. Shoot all 3 rds with each powder charge before moving on to the next charge. Look for 2 or 3 charges that have same poi, pick something in the middle and then do the same when testing seating depth.

An alternate method is to determine what distance you want your load to be optimized for and shoot a ladder at that distance. Shoot one round per charge weight at your chosen distance and look for the charges that have the same poi or least amount of vertical dispersion. If needed, you can repeat the ladder one time or a few times to confirm your findings. Then shoot a fine tuning ladder to test seating depth.
 
Your understanding is correct. You're looking for a series of two or more successive charge weights where the POI on the target remains constant, analogous to vertical nodes on a ladder test. The difference is that when you're shooting groups, the movement of the center point of the group can be subtly more difficult to discern than with a single shot hole. Once you have defined the high/low boundaries of the optimal charge weight window, load to the center of it. You have to define the edges of the window in order to load to the center. Too coarse of a charge weight increment, and you'll only have a very rough idea of where the edges really are. With a .223, you might be able to get away with 0.2 gr increments, but using 0.1 gr increments after the initial coarse charge weight test aren't going to hurt with the small .223 case volume.

The following thread is about Erik Cortina's adaptation of the OCW process. It's only up to about 98 pages at this point, so you should be able to read all the posts in about 20 min or so ;). Nonetheless, it contains mauch good information and example targets. If you're going to use this approach, you may find it helpful.

http://forum.accurateshooter.com/threads/long-range-load-development-at-100-yards.3814361/
 
The 223 is a bench gun .. My 308 is a hunting gun. Our local range only goes to 200 that are working on 300 lanes . I'd like to keep groups under the size of nickel at 200 By throwing charges . IV hade problems in the past finding a stable load for year around use . I know the gun is capable of 10 shot groups around the size a dime . Just can't constantly repeat it for some reason ... From what I understand its because I never found a " non sensitive" load or charge .
 
The 223 is a bench gun .. My 308 is a hunting gun. Our local range only goes to 200 that are working on 300 lanes . I'd like to keep groups under the size of nickel at 200 By throwing charges . IV hade problems in the past finding a stable load for year around use . I know the gun is capable of 10 shot groups around the size a dime . Just can't constantly repeat it for some reason ... From what I understand its because I never found a " non sensitive" load or charge .

I'd think imr 4166 and 140 would be good powders for both target 223 and 308 bench guns... I have a ruger American 308 for a hunting rifle . Was surprised how accurate it was for a factory rifle with 150 grain core locks .. I don't load for it didn't see a need to lol... But I do load for doth 223 and 308 bench guns
 
I'd think imr 4166 and 140 would be good powders for both target 223 and 308 bench guns... I have a ruger American 308 for a hunting rifle . Was surprised how accurate it was for a factory rifle with 150 grain core locks .. I don't load for it didn't see a need to lol... But I do load for doth 223 and 308 bench guns
I never could get IMR4166 to group as well as the other 2 powders I use. IMR4064 is accurate but seems temperature sensitive. The loads I use at 65-70 degrees aren't as accurate at 85-90 degrees. Varget seems good all around.
 
I never could get IMR4166 to group as well as the other 2 powders I use. IMR4064 is accurate but seems temperature sensitive. The loads I use at 65-70 degrees aren't as accurate at 85-90 degrees. Varget seems good all around.
I'd love to find a ton of varget . Can never find it around Pensacola .. How sensitive is 140 ?
 
Move out to 200yd to get a much more clear response. And 2 to 3 shots should be plenty to map out poi.
 
I'd love to find a ton of varget . Can never find it around Pensacola .. How sensitive is 140 ?
If you order online and buy in quantity, it's less expensive than buying locally. I usually buy from MidSouth. It's really whoever can get it to my door for less. Their price is $25.72 per lb and about $23.07 per lb if purchased in 8 lb containers. I usually have to order 5-6 lbs to break even considering the HazMat and shipping cost, but in Ohio, I pay 7-1/2% sales tax on top of the price so sometimes online, I save. You may want to split an order with a friend or two and split the HazMat and shipping cost.
 
Probably be best to just bite the bullet and buy varget for all my rifles .. IV tried all kinds of powders cause I couldn't get varget .the money IV spent could have his got a lot of varget .. I do have 5 lbs of N 140 so would like to try it . Just not Sur how sensitive it is . Weather changes every 10 mins here in fl
 
So its been a long year , IV been everywhere on this earth with work .. So with my 223, 1 in 7 twist Im wanting to try imr 4166 and n140 with 77 gr SMK. From what I understand from Dan Newberry ocw methods are . With different charges at different targets fire groups allow time to cool between shots

. Seating depth at this point is not critical but make the same length. It can be tuned later . ( would I be better off to start at mag length OR just off the lands ? )

Look at the groups , you want the groups that are consistent in same position on the target lets just say 3 groups 19.0 , 19.2 , 19.4 landed at 12 o'clock , and 2 groups landed at 9 o'clock

At this point I would want to test 19.2 again ? Maby shoot 5 more groups and see if that land at 12 o'clock again ? That would be a good load ?

Then start adjusting my seating depth ..
Your general understanding is correct but there is one important element you seem to be missing. When I shoot an OCW I do it with never more than three shots of each different load and I limit the number of loads to no more than six (just my thing so as not to confuse things). This is where you may be misunderstand the procedure. All rounds are shot ROUND ROBIN; one of each charge and each at a different target. Once you are done with that then start the whole process over. The OCW, at least until the node is determined, should be done at 100 yards. Move out in distance only after you determine the 100 yard OCW. The shorter distance is used to take out any shooter/environmental errors.
I shot OCW a few times but have moved to Ladder Testing done at 300 yards instead. I seem to be getting that node down with less shooting and it holds up better at longer distance.
 
OCW dismisses seating, so it's not for finding the most precise load. It's for finding a forgiving load.
If you want best precision, proceed with tested & proven best coarse seating. And then, with best coarse seating AND best powder node, do the tiny tweaking of seating to shape grouping.
I have more faith in distant ladders than OCW.

If you just pull some seating value out of your butt, before/for either testing, you're as likely testing at the wrong seating value, with this muddling up your interpretations. After all, there is no reason for a guess to payoff.
I know most folks do this, and most folks assume seating is a fine adjustment with powder as a coarse adjustment.
It's just opposite.
Once you've done some full seating testing(like Berger's recommended), you learn that seating is by far the biggest adjustment to grouping. It can double or triple group sizes. On the other hand, powder can be adjusted to single kernels(~2fps), and no amount of powder change will triple group size. If you can even double group size with powder, it's likely the wrong powder, or,, you're testing powder with seating in a horrible place.
Anything calibrated is done coarse first, finest last. That's coarse seating first, powder, then fine seating, neck sizing length, etc.

Primers are coarse as well, but not easily adjustable. I couldn't suggest anything there unless your best load workup with a given primer isn't good enough. Then trial & error primer swaps, with more ladders. Or striking adjustments for tightest precision with a chosen primer that you just flat out want to use.

And no matter the components you've invested in (including barrel), there is no guarantee you can get it shooting best on the first try.
 
For the cow, load increments of 0.07% rounded to the nearest 0.1 gr. As was said, shoot round robin. Shoot at 100 yds/m. I would suggest you go to www.ocwreloading.com and review the process.

Pick a seating depth and shoot the ocw. Optimum seating depth can change with pressure and % of case fill. Tweak seating depth after finding your node.

This method can produce extremely accurate loads that don't have to be weighed to the nearest 0.01 gr the way some guys talk about with their long range loads.

Dennis
 
Optimum seating depth can change with pressure and % of case fill.
No it doesn't.
Tweak seating depth after finding your node.
Tweaking is not full seating testing.
This method can produce extremely accurate loads that don't have to be weighed to the nearest 0.01 gr the way some guys talk about with their long range loads.
It can miss an extremely accurate load just the same.

IMO, for long range development, anything dismissing full seating testing is obsolete. It just stands as it did when everyone^ assumed VLDs had to be ITL to shoot. But, everyone^ was wrong, and they wouldn't understand otherwise until Berger proved it.
If you attempt full seating testing while at a best powder node, you'll collapse that node along the way, which is 2 or 3 changes at once. So then you'll settle back to whatever seating you had pulled out of your butt, and powder tested with, except for the 'tweaking' part, for no more than group shaping.
Wow,, must be that's your best seating as well? Isn't it suspicious that a seating guess on your part happened to be best? Well, it might actually be, or it might be a mile from best.
You could always back away from a powder node and do full seating testing to find out. If you do so, and it turns out that best seating is somewhere other than used during powder testing, then at least consider all those interpretations made so far as suspect.
Maybe start over..

If I were to commit to OCW testing for my development, I would first do full seating testing to find coarse best CBTO -while fireforming brass. This would be at a reduced load & fireforming cases twice, primer swapping tests, and if planned well matching H20 capacities. All before moving to powder.
There is progress in this all the way. You don't end up changing or messing with these things once your done.
 
No it doesn't.
Tweaking is not full seating testing.
It can miss an extremely accurate load just the same.

IMO, for long range development, anything dismissing full seating testing is obsolete. It just stands as it did when everyone^ assumed VLDs had to be ITL to shoot. But, everyone^ was wrong, and they wouldn't understand otherwise until Berger proved it.
If you attempt full seating testing while at a best powder node, you'll collapse that node along the way, which is 2 or 3 changes at once. So then you'll settle back to whatever seating you had pulled out of your butt, and powder tested with, except for the 'tweaking' part, for no more than group shaping.
Wow,, must be that's your best seating as well? Isn't it suspicious that a seating guess on your part happened to be best? Well, it might actually be, or it might be a mile from best.
You could always back away from a powder node and do full seating testing to find out. If you do so, and it turns out that best seating is somewhere other than used during powder testing, then at least consider all those interpretations made so far as suspect.
Maybe start over..

If I were to commit to OCW testing for my development, I would first do full seating testing to find coarse best CBTO -while fireforming brass. This would be at a reduced load & fireforming cases twice, primer swapping tests, and if planned well matching H20 capacities. All before moving to powder.
There is progress in this all the way. You don't end up changing or messing with these things once your done.
Am I missing something here? I just got a box of 200.20x Bergers and trying to work up a load. I know 3 shot groups are necessarily accurate but it will give me a starting point to go from. I fired 4 of my old A-Max loads that have never been dialed in, just loaded to the published max load. This is at 215 yards. The Bergers shot low and off to the right. All of these are seated to be .0205" off the lands. The A-Max is a slightly compressed load while the Bergers allow more case volume and are 8 grains lighter with 1/2 the bearing surface. The next test when the mud dries and the wind cooperates will be from 42.2g up to 43.0g in 1/10 increments using 5 shots each. Using the first (41.6) group as an example, I don't think any amount of seating variation would do much. I will play with the jump later but the Bergers are suppose to be a little less sensitive being a hybrid design. I weight sorted the bullets and about half are within .04 grain. These are the others which vary up to 2.8 grain. (200.04 to 200.32 GN)

200-20x.jpg
 
Perhaps optimal seating depth does not change, but when I switched to the Nosler RDF's in my 6.5x47 I first performed a seating depth test using a starting load and found -0.060 to be good. At this depth, all 3 shots were touching. Above or below shots were 1" groups or larger. (I use the Berger test with 0.040" jumps, then test around a good group in smaller steps if necessary) I then did my load development using this seating depth and found a good node. I then did another seating depth test (to me this is "tweaking seating depth") and found that my best depth now was -0.030. I then loaded up rounds at my new load and at +/- 0.2 gr using the new seating depth to test that they would all shoot in the same group. They all shot in a sub 0.5" group. My load was good. This load shoots well to 1100 yds. (Haven't had a chance to take it an farther.) All this testing was done with cases that had been fired multiple times and annealed after every third time.

Performed and evaluated correctly the OCW will produce a load as well as any other method. If you load enough test rounds and then run an OCW, a ladder test (or 2) and the "10 round" method being promoted by some shooters (you are firing ten rounds and primarily recording MV and looking for areas where the velocity levels off) you will arrive at the same place. For me, the primary concern is that I want a method that I have confidence in and that is forgiving in regards to small errors in execution. In a ladder 1 bad shot can skew the results by indicating a false node or hiding a good node. With the 10 round approach, your hand loading/charging procedures must be very accurate and you must have a very accurate chronograph or the results are skewed. With the OCW, 3 shot groups fired round robin are less prone to error. A single bad shot in a group may make the test more difficult to understand, but you can still get a lot of good information from the test to point you in the right direction.

I had been convinced that proper load development should proceed as: 1) Test for best seating depth. 2) Test for best powder charge.
With this last load that I developed, I found a good node but was not completely satisfied with the group, I knew this rifle could do better so I decided to test seating depth again and found that optimal seating depth had changed. Now the only thing that had changed was pressure and % case fill. This had become a compressed load. Perhaps those two changes are not what affected best seating depth but until I find a better explanation I will attribute it to change in pressure, change in case fill %.

T-Shooter, I am trying to read your test above. I am confused about the 4 shots at 41.6. If I am reading it correctly though, there is a scatter node at 41.8 gr which would point to a good node at 42.4 gr. I would suggest that you test in the 42.2 - 42.6 area. I would also suggest shooting these at 100 yds so any wind influence would be very minimal. I would bet that if you load 5 rounds at 42.2 - 42.6 and fire them all at one target you will find that 3 or more of these charges fall into a sub 0.5" group. That will tell you where your node is. I would then do a seating depth test to verify the best seating depth.

To the OP, based on your description I would suggest loading 5 rounds from 19.0 - 19.4 and try what I suggested to T-Shooter. Without seeing your target it is hard to know for sure where to expect your node.

This is just my suggestion. Apparently others have very strong feelings about how things should be done. I have tried several methods and have found what seems to work for me. I would suggest you do so as well. As with many other things in life, there is more than one right way to do this. Each method has it merits and its drawbacks. Ultimately, you are the only one that has to be satisfied with your chosen method and the results.

FWIW,

Dennis
 
Ladder tests predict accuracy nodes by revealing adjacent/successive charge weights that produce the same (or very close) vertical impacts on the test target. Vertical spacing on a ladder test is caused by a combination of velocity (i.e. charge weight) and barrel harmonics (i.e. muzzle launch angle). Velocity dictates when the bullet leaves the bore and the launch angle will affect whether it will impact higher/lower on the target.

Positive compensation is an effect that occurs when bullets moving slightly slower than the average or median of an accuracy node exit the barrel when it is pointing slightly higher. Slightly faster bullets in this same velocity region exit when the muzzle is pointing slightly lower. The higher/lower launch angle for the slower/faster bullets causes them to impact the target (vertically) at very close to the same point (i.e. an accuracy node on a ladder test).

The OCW approach is doing the exact same thing, except that it is using the centerpoint of 3-shot groups as the determinant on the target. You're simply looking for two to three successive charge weights that show minimal group center point movement on the target. The idea is the same as in a ladder test, you're simply using the centerpoint of a 3-shot group as the readout instead of single shots. Successive charge weights that don't cause the group center to move indicate you have found a charge weight window for which the velocity/barrel harmonics/launch angle combine to produce minimal dispersion with respect to charge weight variation on the target. Either approach can be used to reach the same conclusion; however, the interpretation of the two testing procedures is slightly different>>> ladder = minimal vertical dispersion, OCW = minimal group centerpoint movement.
 
Perhaps optimal seating depth does not change, but when I switched to the Nosler RDF's in my 6.5x47 I first performed a seating depth test using a starting load and found -0.060 to be good. At this depth, all 3 shots were touching. Above or below shots were 1" groups or larger. (I use the Berger test with 0.040" jumps, then test around a good group in smaller steps if necessary) I then did my load development using this seating depth and found a good node. I then did another seating depth test (to me this is "tweaking seating depth") and found that my best depth now was -0.030. I then loaded up rounds at my new load and at +/- 0.2 gr using the new seating depth to test that they would all shoot in the same group. They all shot in a sub 0.5" group. My load was good. This load shoots well to 1100 yds. (Haven't had a chance to take it an farther.) All this testing was done with cases that had been fired multiple times and annealed after every third time.

Performed and evaluated correctly the OCW will produce a load as well as any other method. If you load enough test rounds and then run an OCW, a ladder test (or 2) and the "10 round" method being promoted by some shooters (you are firing ten rounds and primarily recording MV and looking for areas where the velocity levels off) you will arrive at the same place. For me, the primary concern is that I want a method that I have confidence in and that is forgiving in regards to small errors in execution. In a ladder 1 bad shot can skew the results by indicating a false node or hiding a good node. With the 10 round approach, your hand loading/charging procedures must be very accurate and you must have a very accurate chronograph or the results are skewed. With the OCW, 3 shot groups fired round robin are less prone to error. A single bad shot in a group may make the test more difficult to understand, but you can still get a lot of good information from the test to point you in the right direction.

I had been convinced that proper load development should proceed as: 1) Test for best seating depth. 2) Test for best powder charge.
With this last load that I developed, I found a good node but was not completely satisfied with the group, I knew this rifle could do better so I decided to test seating depth again and found that optimal seating depth had changed. Now the only thing that had changed was pressure and % case fill. This had become a compressed load. Perhaps those two changes are not what affected best seating depth but until I find a better explanation I will attribute it to change in pressure, change in case fill %.

T-Shooter, I am trying to read your test above. I am confused about the 4 shots at 41.6. If I am reading it correctly though, there is a scatter node at 41.8 gr which would point to a good node at 42.4 gr. I would suggest that you test in the 42.2 - 42.6 area. I would also suggest shooting these at 100 yds so any wind influence would be very minimal. I would bet that if you load 5 rounds at 42.2 - 42.6 and fire them all at one target you will find that 3 or more of these charges fall into a sub 0.5" group. That will tell you where your node is. I would then do a seating depth test to verify the best seating depth.

To the OP, based on your description I would suggest loading 5 rounds from 19.0 - 19.4 and try what I suggested to T-Shooter. Without seeing your target it is hard to know for sure where to expect your node.

This is just my suggestion. Apparently others have very strong feelings about how things should be done. I have tried several methods and have found what seems to work for me. I would suggest you do so as well. As with many other things in life, there is more than one right way to do this. Each method has it merits and its drawbacks. Ultimately, you are the only one that has to be satisfied with your chosen method and the results.

FWIW,

Dennis
Thanks Dennis.
I decided to add 1/10 gn to the Hornady load as a starting point. I had an extra case prepped so just shot 4 instead of 3. This was just the first test to dial these in. I was surprised how far off to the right they shot. I shoot Hornady 168g Match, Sierra 168g MatchKings, and the Hornady 208g A-Max (now using the ELD's) These all shoot to the same area with only a 6/10 mil elevaton adjustment needed for the 208g. I'm doing as you suggest, starting with 42.2 and working up to 43.0 using 5 shots per if I don't run into pressure problems and the groups start increasing in size. Then try adjusting the seating depth. I'm firing at 215 yards so any errors show up easier. I try to pick a day when the wind is low. When the corn gets a little higher, I'll have a 12-15 wide path with 8' high fields of corn on each side to block the wind. If I can consistently shoot 1/2 MOA groups with these, I'll be more than happy.
 

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