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'Little help with OCW interpretation?

Wannashootit

Gunny Sergeant
Full Member
Minuteman
  • Sep 3, 2010
    2,117
    451
    FL
    Had only an hour and half to play at the "short" range for load development, prior to going to 600-1000 the next day at the "other" range with the new barrel.

    The following targets were shot with the 162 AMax from my Savage 7-08 build. The 150 SMK was gnat's ass accurate with the factory barrel, but it was only a 20 incher, lightweight contour and didn't have a fast enough twist for me to risk the 162's, so I changed barrels. Always looking for something better, and after reading all the good reports on the 162, and it's .625 BC, decided to give it a try.

    The following targets were shot in a bit of a rush (read- some shooter error, no doubt) at 100 yards.

    5 loads from 44.0-45.3 grains of H4350 under that bullet. Ten 'foulers' fired from the virgin barrel, then a patch of accelerator, foam with Wipe-Out and then patched it out when the line went cold. No "blue" indication of copper. That was the extent of "break-in"...

    Then on to the round robin. All shots fired within the same 'hot' line of about 20 minutes. Gusty winds about 10-15.
    All about minute of angle (not impressive, yet); odd thing was the last hot round of 45.3 showed only two holes- yet I shot three; and it was at a "clean" cardboard...no other holes...
    So, I either pulled that shot like I've never done before into the next county, or it exactly hit the same hole...

    The chrono results for the 45.3 were all over the road, 2711,2765, and (holy shit) 2848- that's HUMMIN ( and no pressure signs)....so I decided to let that one go.

    Anyway, the 44.6 group showed the least vertical, and if attribute the shot on the right to wind change, it's a pretty tight group.

    That's what I chose to load up for the next day.
    Needed to zero this round at 200, and despite the swirling 10 mph wind got a couple five shot groups where three of them were touching, and the other two close...all sub minute even with the wind (and my wind calls SUCK)...

    20130101_182541.jpg


    Some Chrono results I took while shooting these groups:

    2674
    2674
    2676
    2667
    2686
    2692
    LOW 2667
    HIGH 2692
    AVG 2678
    24.91 ES
    0.91 SD

    The steel at Manatee was non-existent except for one of the small swingers remaining on the left berm, but was able to get pretty consistent hits, considering my ability. Right before the rain came at the end of the day the wind calmed and I felt confident enough to shoot down the ditch to 1000. Punched the data into Strelok and after a couple minor elevation adjustments managed 2 out of three hits before the skies opened up.

    So, it seemed to be shooting pretty well, though neither day had calm enough conditions for what I would normally consider a really good evaluation.

    So, my question is- based on this data, does this look good enough to move onto the next step (playing with the jump for the 162, these were set at about .02, though the OAL gauge was giving me inconsistent readings with this bullet- perhaps because of the extreme secant ogive (?))

    Or, do you think there is there more work to be done?

    New at trying OCW (used to just pick the tightest group) so I'd appreciate any helpful advice.

     
    Re: 'Little help with OCW interpretation?

    It looks like 44.6 is the OCW indicated load. Yes, next step is to do a similar test at different jump distances.

    OFG
     
    Re: 'Little help with OCW interpretation?

    Wannashootit,

    What brass you using? How far off the lands? Barrel length? Sorry for the questions. What you want to see is three groups with same POI, then confirm with 3 charges with 1% of your confirm OCW and you should not get anything larger than MOA. Fine tune ocw with seating depth. Looks like 44.6 as ocw, but 45.0 shifts to the left a little.

    When I was using my 7mm-08 and 162 amax, I found 47.2gr H4350 using Winchester brass and CCI-20 primers.I was getting 2760 fps with 24" barrel. It shot very well and was up on the upper side and max load. I also used 168 vld with 46.6grs around 2740fps.
     
    Re: 'Little help with OCW interpretation?

    I mentioned above that they were seated my "usual" .02 off...
    BUT...and I posted another thread on this and got no response... my results with the OAL gauge and comparator were very inconsistent.

    I have since read elsewhere that VLD's like the 162 Amax might actually have the seating stem bottoming out on the bullet tip, rather than seating them by the ogive.

    Any truth to this? I was getting variations of up to .04 with the comparator and there's never been that much. It really was like it was measuring to the end of the plastic tip of the AMax.

    How do I check to be sure it's seating off the ogive and the tip isn't touching the seating stem?
     
    Re: 'Little help with OCW interpretation?

    I've used RCBS and Redding dies without any problems. Don't know how to check seating stem, maybe some clay or maybe a drop of oil and see if tip is touching.
     
    Re: 'Little help with OCW interpretation?

    I see that RCBS makes a VLD seating stem...
    I've been trying to get through to their CS all day, but it keeps saying a half- hour wait.

    Try again later.
     
    Re: 'Little help with OCW interpretation?

    Agree with OFG on OCW. It appears to me that 44.0 is a scatter node based on the 1 out of 3 impacts being at the same POI. And also that the OCW is generally the around the first and second grouping after the scatter.
     
    Re: 'Little help with OCW interpretation?

    For your next round I would suggest 5 shot groups, gives much better group read.