308 OCW Interpretation Help

Evening Gents,

I'm doing a load work up and I could use some help. First of all, I must throw out a disclaimer that I probably should not have run this test today with fading light. I thought I had more time than I did and there were some EOD guys using our range that ended up getting out later. I should have waited for tomorrow but I didn't and I ended up doing my last string with the headlights of my work car on the target so I could see in the dark. I rushed and some of the groups opened up a bit. All groups fired prone at 100.

I need help picking one out, I thought this would be easier than the ladder test because I can't really interpret those that well either.

DATA: Savage 12 Hog Hunter in 308 w/ Vortex Viper 6.5-20
178gr Hornady AMAX bullets, all cases are FGMM once fired but tumbled, sized, trimmed to length, chamfered, deburred, primer pocket and flash hole uniformed
IMR 4895 powder 37gr - 43gr
Date:10-23-14 1815 hours
Altitude: 3917 Density Altitude: 5949
Humidity: 41.4%
Temp: 74.3
BP: 29.93
No wind

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My interpretation is that they are all low, with a few called flyers in there from trying to hurry etc and some that weren't me. Personally, I like the higher velocity from the 43 load but I had one case show a very slight pressure sign from the extractor and have my reservations about continuing unless we think its still safe.

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Please let me know what you guys think, I could use some pointing in the right direction. THanks in advance.

Respectfully,
Matt

Looks like the lower velocity node came in around the 39.5-40gr mark and the higher velocity node is at the 43gr mark. As for the ejector mark, that's light and not something I would be scared of so long as the primer isn't showing any signs of cratering.

As for where the group is on the target or cardboard, that means nothing other than an indication of velocity compared to the load you zeroed your rifle with.

Great Mr, Baker, kind if what I was thinking as well but wanted to confirm that and that mark on the case. Thanks a bunch.

im with JB...id run that 43g load and tune your seating depth.

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Originally Posted by LongRange

im with JB...id run that 43g load and tune your seating depth.

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+1, tweak it to see if it will get even better. I would also do additional testing of that load at 200 yards to really see what it will do.

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Originally Posted by GaCop

+1, tweak it to see if it will get even better. I would also do additional testing of that load at 200 yards to really see what it will do.

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i agree...i do all my load development at 200-300yds,when i find a good load i shoot it at 500yds to see if it holds together.

I like the faster loads also, but nobody can deny that the 39 grain load has the least vertical spread... I've not chased one of the lower charge weight nodes yet so I'm not sure what would come of it...

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Originally Posted by cowtownup;2862I5

I like the faster loads also, but nobody can deny that the 39 grain load has the least vertical spread... I've not chased one of the lower charge weight nodes yet so I'm not sure what would come of it...

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I agree the 39g load is tight but I bet if he was to try going up .1 or .2 grains at a time the 43g load would tighten up as well and if not seating depth, a primer swap or neck tension would bring it in to shooting 1 hole groups.

OCW evaluation doesn't have squat to do with group sizes. It has to do with where the center of the group is in relation to other charges nearby. If you are gonna just choose the smallest group you don't need to do OCW testing.

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Originally Posted by michaelnel

OCW evaluation doesn't have squat to do with group sizes. It has to do with where the center of the group is in relation to other charges nearby. If you are gonna just choose the smallest group you don't need to do OCW testing.

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and that's why OCD is a waste of time,bullets and powder!!

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Originally Posted by michaelnel

OCW evaluation doesn't have squat to do with group sizes. It has to do with where the center of the group is in relation to other charges nearby. If you are gonna just choose the smallest group you don't need to do OCW testing.

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Shooter skills and equipment might affect the usefulness of these load optimization techniques.

Can someone post a link with a definition and critical review of the the Optimal Charge Weight (OCW) method?

I ask because I have used it to plot both group centers and group sizes. My understanding is that one can identify accuracy nodes by finding where the point of impact slowly changes and to look at group size. While I have turned in a few .3 to .5 moa 5-shot groups, my typical group is more like 1 moa, so tweaking load recipes to knock off .1 or .2 moa becomes a challenge when trying to separate signal from noise.

In other words, the problem with both this method and the ladder is when looks at one shot, or even three shots in isolation, the random nature of shot dispersion can overwhelm any useful signal. This is also why the Round Robin technique is useful -- the aggregate wind, temperature and light conditions affect all groups equally.

Even so, the odd bad or the odd excellent group confuses the message. That's why more shots, for me, at least give more confidence that I've walked the recipe to a good place.

Try this for a read. http://forum.accurateshooter.com/ind...opic=3814361.0

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Originally Posted by JASmith

Can someone post a link with a definition and critical review of the the Optimal Charge Weight (OCW) method?

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http://optimalchargeweight.embarqspace.com/

This is Dan Newberry's site devoted to OCW. Terrible website design, but if you can wade through it, excellent information. It has certainly helped me to develop accurate handloads for my rifles.

Many thanks!

...and it is good information.

Yes I too like the OCW method. BUT... I tried it at 100yds and couldnt make heads or tails. Went to 200 yds and it was quite evident where the nodes were. I HIGHLY suggest getting more distance in your test.
fwiw

I have also had trouble figuring out what I have from my 100 yard groups but have to go a rather long way to get to a 200 yard range, and that one is available only on Friday mornings.

I took to making graphs of the group centers in addition the group sizes. The group center shows less variation than the group size, and we are looking for that slowly changing vertical dispersion node. I go with 3-shot groups because, while larger groups might be more definitive, I am looking for trends. That means that a single high or low center might suggest something, but is more likely the product of the vagaries of the random process. Two or three at about the same height, however, indicate a node is in the area.

The aggregate of 10 3-shot groups is at least as reliable as a single 10-shot group. Of course, doing 5 10-shot groups will give more certain results, but that's a lot of ammunition to throw down range if one does it more than just a few times.

judging by your altitude and 4895 burn rate @ 39.0 gr, Id have to guess that the pill is moving high 2600,s or right at 2700fps.
Its been my expierence that the majority 24" 1-10 twist (if that what the hog hunters twist is) 308,s provide better results at those speeds in 175/178.
Id start working around the 39gr as others have stated as well.

Never rush threw load development. EVER.......The future enjoyment of your rifle, scope, investment and skill all depend on this critical data.
Take your time, every-time or you'll never know you got all she had to offer.
I can't stand the OCW myself and consider it wasteful but that is just because a ladder at 400 will tell me in one session of ten rounds what an ocw will tell me after two sessions and forty rounds. A four hundred yard ladder might as well have a neon sign pointing to the nodes.
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No matter what method you use, take your time.
A wise man (my grandfather) use to say, "if you do NOT have time to do it right, what makes you think you WILL have time to do it over?"

I'd like to hear more about your 400 yard 10 shot ladder test if your willing to share

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Originally Posted by Willoughby

I'd like to hear more about your 400 yard 10 shot ladder test if your willing to share

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Truth be told there is not much to tell as it is painfully simple. So in an attempt to hopefully pass on something useful I'll throw out some background.
I only need a consistent 0.5 MOA or better to consider a rifle suitable for my application however they usually end up between 0.5 and 0.2.
My use of a rifle is primarily between 300 and 1K yards, so 100 yard testing makes no sense because I don't plan on using it there and that is not were I need it to perform.
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My first load development started out overly complicated and took the better part of a 100 rounds three different times for three different bullets and half that again swapping components like powder, brass, primers or "chasing ghosts" in my components. Then finding out my best 100 yard load was not my best 700 yard load and having to backtrack. After all that was meticulously logged and analyzed repetitively and compared I found some frequent redundancies that can and have simplified my hole world ever since.
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1: do not chase ghosts, Wondering if it needs bedded? A:bed it before you even start, Don't be wondering. Not sure about that optic? A: Use one you trust, Higher magnification does make a huge difference in my ability to recognize my own instability so that I can rectify it and remove it from the equation. Don't do load development with anything in question. Your base looks to be a pretty good fit: does it need bedded to eliminate stress so infinitesimal you can't even notice it with the naked eye? A:yes. Does your rifle fit you perfect? It ought to to eliminate the possibility of shooter influence..............Lock down the system before trying to test it.
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2:Shoot your load development during good conditions. You have to test your ability or your ability to deal with poor conditions some other time.
If you have horrible mirage, poring rain or a bad case of the shakes from yesterdays fall from the roof.............. it is not the time.
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3: Trust your components, I do a little research from a number of sources to choose my components for a given caliber and then do not deviate unless it won't shoot to my expectations..........has not happened yet.
Everyone tunes with seating depth except me, I set seating depth right up front with the hornady tool and leave it alone.
While some bullets tolerate jump better than others every bullet I have ever tried likes being close, I can't risk jamming into the lands so I either seat to max magazine length or right around 0.010" off the lands.
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4: Sort your loading components carefully. Brass by weight, do not mix brands. Bullets base to ogive, or use berger.
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5: Loading rounds carefully of course. I run powder increments in 1.0 grain jumps from the low-mid range of my load data up to few a grains short of max, using these loads to get a rough zero at 100 and then on paper at 400. Loading the last few grains up to max in 0.5 for large magnum or 0.3 in small cartridges and then exceeding max load by two increments . Using a 30"x36" target and COMPLETELY IGNORING horizontal....I shoot my batch slowly, making every shot as clean as I can, keeping the barrel cool. Documenting the point of impact in a notebook using my spotting scope: one at a time while the barrel cools.
In ten rounds of progressing powder charges at this distance: you will see dramatic vertical clusters or nodes (completely ignoring horizontal). I then take the tightest group or cluster with the least amount of vertical deviation and determine what powder charge falls dead center of that cluster.
That load WILL make a very-Very accurate and most importantly consistent load. This is all assuming your using consistent components and loading methods and temperature stable powders.
I then load a hand full using that recipe, dial in a true and precise 100 yard zero, use trajectory validation (actual drop needed) at 700 yards to establish my velocity to fill in my ballistic data.
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Using this method and this alone:
We have 2 >>factory rifles<< shooting 0.25" tikka/wsm-win70/wsm and 2 shooting 0.4" sav/338win-win70/7mm .
All the home built savage pre-fit "custom" barreled rifles we use can hold 0.25" or better, the latest can shoot 1/2" groups at 400 yards regularly (thats 1/8 moa).

that's basically the way I do it at 100 yards
but I shoot a lot more bullets doing it
ignore horizontal
start .005 from the lands
load 3 of every half grain- from the middle to 2 grains above max
pick the middle group of the vertical similar groups
if it aint .5 or better - dial chosen load in using coal .010 at a time
I figure if it don't fly good at 100 it wont get any better on out there

I use to do it at 100 and use allot more rounds, probably similar to what your doing.
I started moving it out when it became difficult to determine between the shots. When I got out to my 435 target: the same nine shots that had made a 1" vertical hole the day before threw 2 low and independent then 4 within a 1/2" vertical then proceeded to walk a foot up the page with the rest. back at 100 it made 1" vertical again.
Repeated with the same results. Then got in my log books only to find that, that exact load (the middle of cluster) was already confirmed as shooting all three of the best groups I'd had up to that point.
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Since then, That's all I have needed. My load development and initial zero takes around 20 rounds total, has worked 8-10 times without missing a beat and is producing groups I never would have believed, some of which coming from old neglected el-cheapo rifles (the wife's and the huntin buddy's).

I'll try it
I got a new barrel that needs a load
Thanks much