Noob Question

[Metal God]

Carjunkie , just so we understand each other . I'm not challenging the OCW method . Only explaining why it does not make sense to me and where my confusion is .

My questions have never been fully answered to the point that the light bulb goes on . Maybe I should just talk with Dan about it but I've not seen him on these forums since he introduced the method a few years ago . Like I said in my first post . I have no doubt it's me that has the problem and I'm likely just having a hard time excepting the I idea of fixing something that ain't broke . :banghead:---

 

[CarJunkieLS1]

Metal if you have any specific questions feel free to ask...I'm no expert by any means, but if I don't know the answer I can get the answer straight from the experts.

 

[Metal God]

Load in .5gr increments and shoot each load at a different target. That way you can see where your accuracy nodes are. I'll use my 300 WM as an example I have an accuracy node between 75 and 76.3gr of H-1000. I then took the 1.3gr spread and divided it by 5 which roughly gave me a .3gr difference per test load. Took the most consistent of those (velocity wise) that is your Optimum Charge Weight.

Do you have that data along with targets available to post . That way I can see this node you found and what it looks like on a target as well as the chrono data supporting it ??

A 100yd distance for load development is perfectly fine, because you'll be using a chronograph and that will tell you the most consistent powder charge. You are looking for the lowest velocity spread.

It would seem to me a traditional load development that has a little group and low ES/SD would do the same thing yes or no and why ??

Then there's the idea of COAL and chasing the lead/throat erosion . I have a 308 that eroded .065 in 2500rds . If COAL is so important then that must mean you need to chase that lead . How ever buy doing so you are changing the internal volume of the cartridge which again takes another adjustment . Maybe the OCW method gives you enough wiggle room in pressure that all that is not an issue .

What is your thoughts on that . If tweeking the COAL is so important . do you need to chase the throat erosion ??

 

[ExAgoradzo]

Wow! I fidnt expect this. OK. I'll print this off and read carefully.

Thank you again!

Greg

 

[Bart B.]

I'm too weird to say much more in this thread.

I've never worked up any load; just used the same loads as the match winners and record setters; little difference across them. Different barrels for the same cartridge all shot as good as any without all that fuss. 10- and 20-shot strings gave much more repeatable accuracy results than 3- or 5-shot ones.

One exception; a few of us worked up a load for a new Sierra match bullet for the .308 Win. then loaded several thousand of them for a big international match. We tested different loads at 1000 yards with 20-shot strings; anything less would be statistically insignificant. 20 rounds at random were picked from the two progressive Dillon 1050's loading them that tested 2.7 inch for 20 shots at 600 yards. It shot about 1/2 MOA at 600 and 3/4 MOA at 1000 yards in a few dozen match rifles with all sorts of barrels, chambers and bore/groove dimensions. New unprepped cases, powder metered to 3/10ths grain spread, bullet runout up to .003".

 

[TimSr]

Wow! I fidnt expect this. OK. I'll print this off and read carefully.

Every simple question on a forum turns into an overly complicated debate.

Its near impossible to do a complete workup from home, and one trip to the range without doing a bunch of loads that can be dsmissed before they are fired.

With a rifle I load 3 of each increment. If you have a large spread from min to max, as in many rifle rounds, I start with larger increments of 1 or 2 gr. I may have 4 or 5 loads. I look at groups, look for accuracy trends, and go back home, and do some more fine tuning tests off that load in smaller increments, and as I get closer to optimimum start using 4 and then 5 shot groups for final testing and make more trips to the range.

I also tend to work up more then one load at a time, so my range trips aren't for 10 minute sessions.


If you step through a ten grain spread in .1gr increments, it makes for a lot of loading and shooting.

Load devleopment is one case in which those little hand presses would come in handy where you could work up your load from the shooting bench.

 

[CarJunkieLS1]

Metal: I don't have everything that I did in picture form or even in paper form, however I do have some pics and data that may be helpful to you. I can't post them from my phone, but I'll post here what I have and hopefully it will give a better understanding to what I'm talking about.

Bart B.I don't mean to be rude, but physics don't lie. To have one load shoot the same in several dozen match rifles with different barrels, chambers, bore/groove diameters using holding a .3gr variance in powder charge. That doesn't compute and that seems to be an impossibility from a physics and mathematical standpoint.

A .3gr difference in powder charge WILL have a dramatic effect @ 1000yards. Let's assume you were correct at the .3gr variance causing a 35fps difference in velocity...with the same 7mm-08 load I mentioned earlier @ 2775fps it drops 345.8" @ 1000yds. Lose 35fps to 2740fps 356.3" add 35fps to 2810 and it's 335.74. That means you could have potentially roughly 20" elevation swing from one round to another. That's in one load, one rifle, one barrel, same weather calculations...

Add in all the variables that several different rifles that have different barrels, chambers, bore diameter, etc. IMO it's impossible for them all to shoot the same 3/4 MOA that you state. Way too many variables

 

[Bart B.]

CarJunkieLS1, I agree; physics doesn’t lie. But there’s other physical properties at work.

If the barrel does not move in any way after the primer fires, burns the powder, gases push the bullet through the barrel and exits, then indeed velocity spread will cause vertical stringing of shots caused by drop differences at target range. But that doesn’t happen. Go through the following in order listed and hopefully you’ll understand.

Recently, Geoffery Kolbe (owner of Border Barrels) presented the following:

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm

Over a hundred years ago, the Brits proved why their SMLE’s shooting the 303 with a big muzzle velocity spread shot so accurate at long range. Click on the "PDF" link in this one to read it:

https://archive.org/details/philtrans05900167

Varmint Al’s website has several pages showing how barrels whip and wiggle before the bullet exits along with ways to “tune” the barrel’s resonant and harmonic frequencies to let the bullet depart at the right angle to compensate for it’s velocity so it’ll strike the same place down range.

http://www.varmintal.com/a22lr.htm

http://www.varmintal.com/aeste.htm

http://www.varmintal.com/alite.htm

http://www.varmintal.com/amode.htm

http://www.varmintal.com/atune.htm

http://www.varmintal.com/apres.htm

And finally, here’s Kolbe’s site that lets you plug in your .308 Win barrel’s profile dimensions and some load data to see where the bore axis points upon bullet exit. It only covers the barrel whip in the vertical plane in a free recoiling rifle. It will be less in a hand held rifle and also have some horizontal whipping because the center of mass holding the barreled action will not always be in the vertical plane of the bore/recoil axis.

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/barrel_vibrations.htm

This is also a good explanation as to why several people shooting the same rifle and ammo will have different zeros with them.

The Browning BOSS works on this principle. Smallbore shooters often use tuners on their barrels as do some short range benchrest folks. Longer barrels used in long range matches typically have enough whip by themselves that no tuner's needed.

A half grain of powder will change the vertical average point of impact, but the accuracy will stay the same if the load's in a good range of charge weights to start with.

Regarding a given bullet having good accuracy across all sorts of bore and groove dimensions, as long as it's diameter is larger than the groove diameter, it'll shoot just fine. I've shot 30 caliber bullets at .3082", .3084" .3087", .3088" and .3092" in barrels with groove diameters from .3070" to .3080" and bore diameters from .2980" to .3010" all with equal accuracy at any range.

When the Brits switched from their .303's to the 7.62 NATO round for their long range fullbore matches where they had to shoot arsenal ammo (no handloads allowed). some lots of their arsenal 7.62 NATO rounds' bullets were only .3070" diameter. They had to get barrels made with .3065" groove diameters to shoot them well; they did great with them. A couple of that size were used shooting Sierra's new 30 caliber 155-gr. Palma bullet at .3084" diameter into about 3/4 MOA at 1000 yards.

 

[Dave P]

Bart Sez: " What's happening in reality is the load's tuned to be at the right place on the barrel's upswing so those leaving at a slower speed will depart at a slightly angle above the LOS than faster ones that leave at a lower angle."

This is the beauty of finding that most tolerant load. And as I recall Varmint Al's graphics show the barrel swinging up down, as the primary movement .

However you chose to find that load (Audette/ladder/OCW/trial&error), go for it. I have multiple successes with loading just ten rounds to find that sweet spot using Audette's method (it looks like he preferred 20-30 shots on target).

 

[CarJunkieLS1]

That's the point of OCW development it's to find a window that the rifle shoots most accurately. If you load up min to max in .5gr increments and you pick the most accurate you could be at the edge of the accuracy "node" meaning as weather changes, and slight variations in powder charges seating depth pressure curve etc. Its possible you pull yourself out that window. You could have a 3/4moa load on one day than 3 months later you have the same load shoot 1 1/2moa.

 

[Metal God]

The interesting thing about what Bart and Dave both posted is that I found that same thing in my loads .

For rifles , and not completely confirmed but It seems my rifles like a velocity for a particular weight bullet more then anything else . It does not seem to matter much what bullet ( with in reason , I'm talking match bullets ) like 175gr smk or 178gr A-max . as long as my muzzle velocity is around 2560fps . That load will shoot well . Powder does not seem to matter much either as long as they are close in burn rate

In this case a 175gr smk @ 2560fps is mid to upper 2/3 charge range of the powders I use . I did not notice the pattern for quite some time . I keep pretty detailed notes on loads and after looking back through all the notes a pattern started to form .

I had tried on many occasions to push those loads faster with the same accuracy but never could do better with out pressure signs and what not .

It appears I have come to the same conclusion in 2k rounds of data . The thing is I can't see that in one set of load development . Sure I may have been able to find that node it real fast but that would not have concluded anything .

How ever I now look back through my binder of 308 load data sheets and I see one thing that seems to be the same . A 175gr or 178gr match bullet leaving my barrel at 2550fps will likely be very accurate . What case or powder I use does not seem to matter . Primers till just recently have always been Win .

 

[Nature Boy]

For you OCW experts, what does this tell you about my attempt a couple of weeks ago?
.308 168g AMAX and Varget

 

[Metal God]

It says 3 shots does not say much . Run that whole test again if the results are virtually identical you then can draw a conclusion .

Actually I have no idea what those targets represent . I'm looking forward to the opinions of those that can draw a conclusion . I see NO OCW node there . of coures I have no idea what to look for

 

[Bart B.]

Statistically, they're all equal as far as I'm concerned.

But the important thing to me is, their group centers are not at the same place relative to the aiming point. There's at least a half inch spread in group center points.
You did use the same aiming point for all; right? And you hand held the rifle as it rested on something; right?

Shoot five 3-shot groups with each on a single target atop a backer that'll show the 15-shot composite. Then compare that 15-shot composite for each load.

I'm not an OCW expert, so my opinion may not matter.

 

[CarJunkieLS1]

42.4-43 seems to be the node. With 43he being the upper end of that node. Any idea what your bullet jump is...I'd load 42.4-43 again and move your bullet .010 in each direction. BTW do u have any chrono data

 

[Metal God]

I don't see it . I keep looking at those targets and see nothing that says a couple of them combined is likely a sweet spot . Most are high left but then each one compared to the ones top and bottom seem completely different .

The one thing I do notice is that it appears you have already narrowed the charge from the books minimum 32.6gr and max 44.0gr to a 1.5gr with in the min to max area . You then are trying to find the node with in that 1.5gr area . Isn't this the point you start changing seating depth because that 1.5gr area is the node ????? So you take 42.4gr the middle of your node and start working the COAL . ?????

Carjunkie posted while I was Writing . Looks like I'm in the ball park

The other interesting thing I noticed was not one of them was under MOA . This makes me wonder two things . Did you push the first load development to the max charges . I've never used Varget but have read MANY times it's best very close or even a tad over max charge .

The other thing I'd like to know . Were there other groups that were sub moa in the initial load work up ?

 

[Bart B.]

What if Nature Boy's rifle and ammo is really a 1/3 MOA system accuracy wise but his own shooting skills don't let it be seen?

 

[Metal God]

Bart:

I was trying to get to that point by first removing other variables . Did not want to come out and say if those were my final groups to work with and fine tune I'd scrap the whole cartridge combo . I've done some COAL adjustments to try and fine tune loads . Although I feel I've had some success in doing so . Never have I been able to change a 1.25moa load to a 1/2 moa load or cut the group size in half just by changing COAL .

I'm very interested in seeing his next set of groups when working with the COAL .

 

[zb338]

I would just like to caution you not to set the shoulder back on the .338
as you keep reloading the cases. Depending on your rifle you can get
head separations. The belted case holds the cartridge against the bolt
face. Either partial size or neck size. Inspect your fired cases carefully
with special regard to the portion above the belt (the head). It's a great
hunting cartridge. Have fun.
Zeke

 

[Bart B.]

Zeke,

Are you saying all H & H belted case heads are held against the bolt face when chambered as well as when fired?

If that's true then all such belted cases and their chambers in barrels must all have exactly .220" belt headspace. SAAMI specs for the .338 Win Mag allow .220" to .227" for the chamber and 212" to .220"'for the case.

People have been full length sizing fired H & H belted cases for decades bumping their shoulders back a couple thousandths each time for 15 to 20 reloads per case. They then headspace on their shoulder with a couple thousandths head clearance to the bolt face. No head separation problems at all. New cases typically have more head clearance in commercial chambers.

No rifle I know of with correctly sized cases have the case head against the bolt face when fired.

 

[CarJunkieLS1]

Here is what seating depth adjustments can do. This is the same exact load except for seating depth is all I have changed. in .010 increments.




Those are 5 shot groups see how the vertical stringing is non existant it because the powder charge is where it needs to be, the chrono proves that also as those 15 rounds had an ES of 11 and a SD of 5.

COAL tuning is very important in my experience the pics I have are typical of what I see when using the OCW method. Just by tuning the seating depth I was able to turn a load that was easily 1.5MOA to a load that consistently is 1/2 moa or better. That 5 shot group in the pic measured in the .3's

 

[Metal God]

Well that's pretty impressive . That top picture is 3moa if shot at 100yds . To change a 3moa load to a 1/2 moa load is hard for me to wrap my head around but I have no reason to think you're misrepresenting the load .

That just makes me wonder how my rifle that has gained .070+ of lead do to throat erosion still shoots the same load with the same OAL just as well as it did when it had .060 less of a jump . Maybe I just got lucky . I can say that rifle dous not shoot Fed GMM as well as it once did .

Things that make you go hmm

Kinda looking forward to Barts take on COAL and how much he thinks it effects accuracy

 

[CarJunkieLS1]

Yes that was shot at 100 yards. I admit I was skeptical when all my long range shooting buddies were explaining OCW develoment to me and what the groups I shot were telling me. After using OCW for the last 4-5 rifles I have loaded for with impressive and consistent results I'm a believer.

It's what all the shooters I know use and Darrell Buell uses it too, if its good enough for the Team Captain for the US FT/R team its good enough for me.

 

[Saintsfan1977]

Actually I have no idea what those targets represent . I'm looking forward to the opinions of those that can draw a conclusion . I see NO OCW node there . of course I have no idea what to look for

I don't see it . I keep looking at those targets and see nothing that says a couple of them combined is likely a sweet spot . Most are high left but then each one compared to the ones top and bottom seem completely different .

You are looking for the center of the group to be the same across different grains of powder.

Group 1= 41.8gr The center of the group is right next to the bulls eye. 1/2" up and 1/2" left
Group 2= 42.1gr. Look at the center of the group. 1" left and 1"high.
Group 3= 42.4gr. 1" left and 1/2" high
Group 4= 42.7gr. 1/2" left and 1/2" high
Group 5= 43.0gr 1" left and 3/4" high
Group 6= 43.3gr 1/2" high and 1/2" left
Group 7= 43.6gr Call it 1/2" high
Group 8= 43.9gr 1/2" high and a hair left

The closest 3 groups would be 42.4- 43.0
The middle of these charges showed 42.7 to be different but the next charge went right back to 1" high and 1" left

Its the closest ones that need to be checked again and in between these charge weights by .1 to .2 gr.

The 42.7 should actually be closer to 1" high and 1" left though so it leaves me scratching my head but its the only group that comes close without as much variation.

44.2 might over max but it should be close to 1/2" high and a little left.

What you are looking for is the center of each group to be close to the same on about 3 consecutive powder charges. That lets you know you are in a node. Hard to tell on this target though. I would shoot it again to verify it.

 

[Metal God]

The closest 3 groups would be 42.4- 43.0
The middle of these charges showed 42.7 to be different but the next charge went right back to 1" high and 1" left

Its the closest ones that need to be checked again and in between these charge weights by .1 to .2 gr.

The 42.7 should actually be closer to 1" high and 1" left though so it leaves me scratching my head but its the only group that comes close without as much variation.

This is really where the OCW method makes no sense if what you are describing is in fact what you do . I thought the OCW was to give you a load that works well in a rather large charge range At least 1gr spread/window where there is virtually no effect on accuracy in that charge range . Why then is it necessary to start checking charges inside that window by .1gr or .2gr increments . It would seem logical if the OCW method does do as reported . You load the charge that's in the middle of that window . You then have a pretty big widow/spread of pressures that will not effect POI .

One thing I'd like to see is where those centers would be with 5 shot groups . It sure looks like every load has a flyer in just 3 shots . I can't tell you how many spectacular 3 shot groups I've had . Every shot after almost always grows the group . and the randomness of each POI would seem to slightly change the center of the group as shot count goes up .

3 shots at 300yards


3 shots at 100yards


3 or 4 shots at 100yards


4 shots at 100yards


Not one of those groups represents how well I and my rifles shoot consistently . I had one group I was shooting one day that after 7 shots in a row less then a minute apart there was one hole in the target that did not measure more then .4" at 100yds . I was looking at the group through the scope and wandered how many shots I could put through that hole . The next shot hit 3/4" high & right . Turned that sub 1/2 moa group into a 1.1moa group and shifted the center 1/2" .