FYI-6.5 Sherman, 156 & Retumbo

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by dok7mm, Sep 30, 2019.


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  1. bruce hanson

    bruce hanson Member

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    Ooops big fingers on small phone created post accidentally.
     
    Last edited: Oct 2, 2019
  2. bruce hanson

    bruce hanson Member

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    I have been reading information on this site for a couple of years. As a matter of fact because of some information on here I switched from R17 to Retumbo in my 6.5x284. I gained only about 50fos, but it cut my group from .6 to .25 which is great.
    I don't know what I bumped to make the last post, but I suppose that made everyone curiouse so I may as well join the conversation.
     
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  3. dok7mm

    dok7mm Well-Known Member

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    UPDATE : I was short of time today, but I did shoot a reduced charge of 59.0 gr Retumbo with the 156 eol @ 100, just to check out seating depth on 6.5 Sherman.

    Doesn't seem to be much change with this bullet up close when you factor in conditions and shooter error. I wanted to find a bit tighter
    seating depth, prior to shooting groups up to max velocity. Hope to get to that on Friday.

    Fifteen to twenty thou jump seems to be sweet (for now).

    Did the same seating test with 156 in the 6.5 SS and .030" jump was as small as I can shoot. IMG_20191002_142128657.jpg
     
  4. reeldawg

    reeldawg Well-Known Member LRH Team Member

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    tagging in
     
  5. dok7mm

    dok7mm Well-Known Member

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    Finally got around to jumping the Retumbo charges in my 6.5 Sherman & 156 EOL in 26" 3B.

    CBTO-2.894", COAL-3.586", .020"
    jump changed from 10 to 20 thou
    ( not sure if this was smart). New
    Retumbo lot # of 16 pounds. I also moved to 200 yd, 3 shot groups. I don't know if the groups were my fault, the conditions ( wind was 3-7 mph and from 9:00 to a 12 mph head wind) or my seating depth change. Take your pick! Temperature varied from 68* to 76* over session.

    I'm now going to load up 5 shot groups from 63.2 up to 64 grains and try them at 400-600 yds and see what happens.

    Also, I ran a one shot pressure test in my 6.5 SS with my new 10# of N-565. Loaded 58 to 62.5 grs with 156 EOL in my 24" Bart 2b. My only pressure sign was a slight smear @ 62.5 w/temp at 80* to 84*. 61,61.5 and 62 went in same hole @ 100.

    6.5 Sherman & 156 pictures below. IMG_20191004_161619568.jpg
    IMG_20191004_161559153.jpg
     
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  6. dok7mm

    dok7mm Well-Known Member

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    I like my first outing with the new N-565, it looks to average 20 fps increase per 1/2 gr over 10 loads in the 6.5 SS. Rich was spot on in suggesting this powder for this cartridge. I'm impressed, at least for now.
     
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  7. Bro Dave

    Bro Dave Well-Known Member

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    What do you mean if the groups were your fault? I hope when I grow up I can shoot 200 yd groups like those
     
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  8. dok7mm

    dok7mm Well-Known Member

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    It's one thing to have groups increase in size when you have high ES, but groups with low ES that shoot about the same...........
    they are usually my fault.
     
  9. dok7mm

    dok7mm Well-Known Member

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    My final dope with 6.5 Sherman is done. 156 EOL, 63.8 gr Retumbo, CBTO - 2.904", jump .010", 26" 5R 3b, 200 yd zero @ 1575' elevation,
    70*, 28.40 Hg, 50 % humidity.

    My Labradar was showing 3,127 fps average, but drops @ 600 yds were calibrated to show 3,050 for my accuracy load.
     
  10. rockwallraider

    rockwallraider Well-Known Member LRH Team Member

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    I had the same thing happen with my lab radar @ my 500 yd drops and finally realized it was my scope dials being off by a little
     
  11. Capt RB

    Capt RB Well-Known Member

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    One of the biggest reasons for the discrepancies for speed or bc is that fact. If more did a tall target test they would see it and then you can change your per click adj amount to make it line up. It's not always the reason but it is more common that talked about
     
  12. elkaholic

    elkaholic Official LRH Sponsor

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    First thing I do when I mount a new scope is calibrate it. I usually measure at least 20 moa at about 50 yards
     
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  13. dok7mm

    dok7mm Well-Known Member

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    I did a tall target test when I bedded a new rail, changed rings and put a new barrel on. The March is good to go.

    It's more likely the result of the 5-7 mph headwind.
     
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