Len Backus- Please tell us about the 7mm Dakota

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by CanadianLefty, Mar 1, 2005.

  1. CanadianLefty

    CanadianLefty Well-Known Member

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    Hello Len,

    From what I've read, you have 1-3 rifles set up in 7mm Dakota.

    Please tell us a little about your cartridge choice, brass quality and real world velocities (compared to 7mmSTW or RUM).

    Finally, why the 7mm Dakota vs. the .300 Dakota?

    I also read that it is possible to form Dakota brass from Ultra mag. cases by using a redding case forming die in .404J. Is this doable?

    Big Thanks!
     
  2. Len Backus

    Len Backus Administrator Staff Member

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    CL

    I've been a 7 Dakota user for about 3 years or so. I would consider it to be a ballistic twin of the 7 STW since the case capacity is within 1 grain. I got started on it when I bought an in-stock custom rifle. I was asking around for an available rifle in 7 STW and got steared toward a great rifle in 7 Dakota.

    I buy the Dakota brass through Midway...around $26 for 20 pieces if I remember. I don't shoot brass all that long but I think you could get around 20 firings if you weren't pushing pressures too high. Initial case neck runout is around 6 or 7. I once challenged Don Allen about this and he took some of my high-runout returned brass and fired a .3 something group with it.

    I bought 200 pieces from someone on LRH.com a couple months back and the runout was around 2. So maybe I just got 6 or 7 unlucky lots over the 3 years?? Anyway, the initial runout doesn't matter after the first firing. The cases also seem to be too short for saami specs. They always stretch in base to shoulder length about 15 or 20 thousandths at first...and this is with rifles chambered with reamers from 3 different sources.

    With a 176 grain Cauterucio (.750 bc) and 76 grains of H1000 I get between 3100 and 3150 with a 26 inch barrel. It varies a little depending on the barrel. These are fairly hot loads. Minor casehead marks and an occasional sticky extraction.

    I never considered the .308 version because I have always been a proponent of using the best bullet BC and the .284 is quite superior to the .308 given the same bullet weight. And of course, you can drive a given weight .284 bullet faster than with a .308 bullet.

    Don't know about the case forming question.
     
  3. Mysticplayer

    Mysticplayer Writers Guild

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    If I may bud in, you can form Dakota brass from RUM. Base dimensions are different but not a big deal. Just big work.

    I am looking into a similar project and going to stick with the STW because brass is dirt cheap and I still have some from my Wby days.

    Also, my barrel will be long (28 to 32"). Or else, there isn't that big a gain over the 7RM with 160 class bullets. Get's tough buying these boutique bullets in Canada. Hornady stuff is readily available as is Wildcat bullets.

    Richard may be making some heavy 7mm. Don't know for sure.

    Ballistically, the 6.5 and 7mm are way better then the 30 or 338 cal until you get into their heaviest bullets. Recoil is substantially higher too.

    I use the 300RUM and 338 Mystic simply because I want a really big bullet arriving at the LR game. Otherwise, I shoot my 6.5 and get the same ballistics. The 7mm simply fills the missing calibre gap in my gun chest.

    Jerry
     
  4. Brent

    Brent Well-Known Member

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    And of course, you can drive a given weight .284 bullet faster than with a .308 bullet.

    Len,

    Are you saying a 180 gr bullet out of a 7mm can be driven as fast as a 180 gr bullet from a 30 cal at the same pressure? I do realize the BC of 30 cal in the same weight bullet will be lower than the 7mm. Same case, same powder, a .338 will drive a 180gr faster than a 30 cal due to friction and other factors which make it more efficient.

    I can get 3250-3300 with a 180 in the 26" bbl 300 Ultra, not sure what the 7 Ultra would.
     
  5. Len Backus

    Len Backus Administrator Staff Member

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    Brent, my brain is still recovering from my trip and that was a totally wrong statement by me. I know better. Thanks for correcting me.
     
  6. Brent

    Brent Well-Known Member

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    Seriously, I thought you were onto something, Len, and was really interested in what you were seeing with your 7's, even though it did go against conventional wisdom so to speak. Now I'm friggin disappointed! I'm still doin a 176 throated 7 Ultra, dammit! /ubbthreads/images/graemlins/smile.gif
     
  7. speedbump

    speedbump Well-Known Member

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    Brent,

    I get a comfortable 3,360fps with a 176C from my 30" barrelled 7mmRUM. 5010 pulldown works best, but Retumbo is OK.
     
  8. Brent

    Brent Well-Known Member

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    Speedbump,

    Sounds about right because I get about 3550 fps out of the 30/338 Lapua Imp with a 178 A-Max in the 30.5" tube.
     
  9. trophyhunter170

    trophyhunter170 Active Member

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    Len,

    I have just completed a 7MM Dakota Imp. build on a Stiller TAC300 Action and a Krieger Rem Varmit Taper 26" Barrel, McMillian Game Scout Stock. My case design increased case capacity 6.7 Grains and I am planning on trying Retumbo and H1000 powders. All I have done is broke my barrel in and fireformed my cases. Waiting on my dies before I start working up loads so I will not over work the necks.

    My questions is how are the 177 Grain Caurterucios for Long Range hunting out to 1000 Yds.? Also any suggestions on seating depth? I also have 180's in the Berger VLD and JLK's. The Caurterucios have such a great BC that I thought I would start with them provided they kill effectively.

    Thanks,
     
  10. Len Backus

    Len Backus Administrator Staff Member

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    The Cauteruccio is a great bullet at the range you mention though I never shot an animal past 720 with them. I later learned that the bc can't possibly be as high as someone had told Bob C.

    It must be about the same as the Berger 180, maybe a tad less.

    We all now know so much more about accurate bc testing than we did back then.

    I switched to the Bergers a few years ago.
     
  11. trophyhunter170

    trophyhunter170 Active Member

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    Len,

    Thanks for your info. Is the terminal performance of the 177 Cart. on deer size game equal to the 180 Bergers?

    Also I just got some info you might be interested in on all these bullets from a very well known person in the long range game and here is what he stated.

    Have measured the BC's for all the bullets you mentioned, they are as follows. Note these are G1 BC's, all averaged from 3000 to 1500 fps.

    Berger 180 VLD: .659

    Berger 180 Hybrid: .674

    JLK 180 VLD: .645

    Cauterucio 177 VLD: .683

    Cauterucio 189 VLD: .703

    Of course BC does not come into play unless they are effective for hunting and are accurate. Just trying to start with what gives good down range terminal killing performance and highest energy when I start working up loads. Want to make my barrel last as long as possible.
     
  12. Len Backus

    Len Backus Administrator Staff Member

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    Yes, I think so.