OCW results. Opinion wanted!

scissorhands

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Shot these today. Rifle is a Savage 12 FTR .308. Lapua brass, varget powder, Federal primer, .018 off the lands. All rounds were shot in a round robin @ 3 shots each Any input? First time trying the OCW method. I'm kinda puzzled.....

Thanks,

Rob
 

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Pinecone

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Feb 21, 2013
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What is each POA?

As I understand it, with OCW you are looking for the 3 groups that group the same direction from the POA. Say 1 o'clock.
 

RyeDaddy

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43.2 or 43.3. Groups on either side are same point of impact more or less. Also, the flier in the 42.6 group indicates a "scatter node". According to Newberry OCW should be 1.5%-ish above that. 42.6 + 1.5% = 43.23.

That 43.2 group looks great as is.
 
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sigma2chi

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I'm about to do my first OCW test and I'm starting with a .010 jam into the lands. Could his seating depth be affecting his OCW test??
 

shoot4fun

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    I'm about to do my first OCW test and I'm starting with a .010 jam into the lands. Could his seating depth be affecting his OCW test??

    I recently did an OCW on a new AI 260 barrel with 142 SMK .010 in the lands. I was not happy with the potential it showed but proceeded to complete the test, pick an node and work on final seating depth. I backed off in steps out to .016 off and that is when I hit the accuracy I had hoped for. So while I don't think where you seat them initially important I would probably start about .010 off in future tests.
     

    oldfatguy

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    The reason to start with the bullets 0.010" jammed is to find out where the pressure signs show up. Usually a jammed load will produce more pressure than the same charge with a jump.

    This is covered here in a sticky, I think.

    OFG
     

    shoot4fun

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    The reason to start with the bullets 0.010" jammed is to find out where the pressure signs show up. Usually a jammed load will produce more pressure than the same charge with a jump.

    This is covered here in a sticky, I think.

    OFG

    Pulled from Newberry's website instructions:

    6. The seating depth for all test loads should of course be the same. I normally seat the bullet a caliber's depth into the case, or to magazine length--whichever is shorter. I don't believe loading to approach the lands is necessary, or even desirable in most situations. So long as the bullets are seated straight, with as little runout as possible, the advantages of loading close to the lands are largely over-stated. This said, be certain that the seating depth you choose does not cram the bullet into the lands. Stay at least .020" or so off the lands for these excercises.

    This is what I would do. Anyway, what if the throat is SAAMI and your bullet can't stay in the case and hit jam?
     

    scissorhands

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    I loaded .018" off the lands because I read somewhere on here one of the top Savage shooters recommended his load was best at 43gn of varget .018 off the lands.... I thought why not..... seems to work pretty good so far

    Rob
     

    RyeDaddy

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    Dude, use 43.2. It's obvious and right where you said others with your rifle found their load (within 0.2 grains).

    It was asked rhetorically above by shoot4fun whether those were scatter nodes or just disappointing shots. The fact that the 2 odd groups with fliers are 1.5% above and below the tightest group that also has the same POI as the groups on either side points to those being scatter nodes if you subscribe to Newberry's theory on OCW. It also points almost definitively to 43.2 being your OCW.

    Load some and try again, run them over a chronograph to see what your velocity spreads are, I'll bet they look good. Shoot4fun gave you good advice if you wanna play around with it and see if you can come up with anything better, but I'd go with 43.2 with the shortage of components at present.
     
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    scissorhands

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    Dude, use 43.2. It's obvious and right where you said others with your rifle found their load (within 0.2 grains).

    It was asked rhetorically above by shoot4fun whether those were scatter nodes or just disappointing shots. The fact that the 2 odd groups with fliers are 1.5% above and below the tightest group that also has the same POI as the groups on either side points to those being scatter nodes if you subscribe to Newberry's theory on OCW. It also points almost definitively to 43.2 being your OCW.

    Load some and try again, run them over a chronograph to see what your velocity spreads are, I'll bet they look good. Shoot4fun gave you good advice if you wanna play around with it and see if you can come up with anything better, but I'd go with 43.2 with the shortage of components at present.

    Cool deal, just didn't expect to be done with the testing so quickly. Thanks for all the help.

    Rob