.243AI and 115gn DTAC results

Discussion in 'Ammunition and Reloading' started by spamassassin, Jan 15, 2018.

  1. spamassassin Well-Known Member

    Member Since:
    Aug 8, 2014
    Message Count:
    1,156
    I took the hot dog gun out yesterday to get some velocities on a new load and check grouping. Sierra and David Tubb had changed the design of the 6mm DTAC 115gn recently to include a rebated boat tail. The BC changed enough upward that I decided to start using those and ditch the 108 ELD-M's since I was also out of ELD's. It was a good time to change. So, I ran up some loads at .3gn under my 108gn load and those did really well. From the drops I was getting a bit over 3100fps (didn't get any data from the chronograph, low batteries). Only 5.3mils of drop at 900 is really cool at sea level in the cold. Pressure signs didn't show up so I cranked it up .3gn back to my normal match charge weight. The bearing surfaces and weights are really close between the two bullets and I've got a good whack of case capacity left so I'm not worried about overpressure at that point. I have also just flipped scopes around on my rifles and had a new/old US Optics SN-3 3.8-22x58mm that I'd just put on and I needed to get a good zero before next Sunday's match. Ammo loaded and gun set up so I ran off to the range and did 20 rounds of quick work. It took a while to get the zero because I couldn't have my spotters up to the line (local range rules sucketh). After pushing in 4 mils of left and one mil of up I had a good POA/POI and stopped messing with the turrets. I was using a Magnetospeed while getting my coarse zero and I looked to see what the results had been. I got 3184 average with an SD of 4 after 10 rounds. Just exactly where my last load was with the 108gn ELD-M's.

    Load Data:
    45.5gn RL-23
    Hornady Brass fireformed +1x fired.
    WLRP
    .080 jump
    neck size only.

    Group size was .580 for 10 rounds.
    wood chucker likes this.
  2. Keith Moderator

    Member Since:
    Dec 7, 2014
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    A rebated boat tail? Does that look like a rebated head on a case?

    Out of curiosity, I've read magneto speeds effect the point of impact when in use compared to when no in use. As often as I seem them being used by people, I'm wondering about the validity of that.
  3. spamassassin Well-Known Member

    Member Since:
    Aug 8, 2014
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    [IMG]

    That's basically the same differences but those look like 30 cal scenars. The rebated tail obturates better to fill the bore in theory and reduces the surface area that is susceptible to the normal drag on the back end of the bullet. They're also a closed point JHP, sierra does an extra pointing operation on them.

    Magnetospeeds normally will induce a small POI change. Sometimes it's even kinda big. For me it moves my POI up and to the right about 1.5 inches on my .243AI with heavy bullets but doesn't cause groups to open up. On my .223 there's no really obvious change at all with my 73gn ELD load. Direction and magnitude of impact shift vary gun to gun and load to load. It's all to do with harmonics. Once you characterize how it affects your gun, then you can do quite a lot with it attached.
    wood chucker likes this.
  4. Keith Moderator

    Member Since:
    Dec 7, 2014
    Message Count:
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    The bullet is how I envisioned it then.

    Thanks on the info on the magneto speed.

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