7mm 197g SMK

Discussion in 'Big Stuff -- 6.5mm, 7mm, 30 Cal' started by kyreloader, Aug 25, 2017.

  1. kyreloader

    kyreloader Gold $$ Contributor

    Joined:
    Dec 24, 2009
    Messages:
    723
  2. Yote Hunter

    Yote Hunter

    Joined:
    Feb 28, 2015
    Messages:
    144
    Have very limited testing so far but much more to come. A friends 28 Nosler with approximate 0.005" jam and 85.0 gr RL 33 and CCI 250. 1:8.3 twist and 28" Bartlein. Approximately 3100 fps. 4 out of 5 shots were 1.5" at 500 yards. Wasn't sure where shot #5 went due to off target and other bullet holes. Showed a lot of promise for first group. I shoot a 28 Yukon (28 Nosler with shoulder pushed back for a .340" neck) 30" 1:8.3 twist Bartlein. 84 gr RL 33 and CCI 250 and 0.005" jam gave approximately 3100 fps also. Shot 4 shot group around 1.5" and the 5 shot group was 2.5". First group with this bullet and gun combo also. Will try to get to the 3150 fps accuracy node and different seating depths. Believe it will do well with tuning.
     
  3. LA50SHOOTER

    LA50SHOOTER

    Joined:
    Jan 30, 2010
    Messages:
    33
    Yote, - Do you think that I'll be able to run the 197 gr in a 28 Nosler with a 1-8.5 twist ? - I have 2 barrels both throated for the 195 Berger and the barrels are 34" in length. - Plan will be to try to use RL-33
    Thanks, Ron
     
  4. Yote Hunter

    Yote Hunter

    Joined:
    Feb 28, 2015
    Messages:
    144
    LA50SHOOTER, There should not be a stability issue with an 8.5" twist. I use an 8.3" as stated. At my elevation and a speed of 3100 fps and elevation of 700' at 70 degree temperature an 8.5" twist Has full stability according to the Berger twist rate calculator. The 197 gr Sierra Matchking has an OAL of 1.667". Use the Berger Twist rate calculator using your elevation and temperature that you intend on shooting in and see if you get a full SG # of 1.5. If not it shows how much your BC is compromised. A stability in the high 1.4xx range is still pretty good.
     
  5. kyreloader

    kyreloader Gold $$ Contributor

    Joined:
    Dec 24, 2009
    Messages:
    723
    Thanks Yote Hunter. Glad to know that 5 in worked for you for seating depth.

    Anyone else trying out this bullet have any input?
     
  6. Yote Hunter

    Yote Hunter

    Joined:
    Feb 28, 2015
    Messages:
    144
    The reason why I was using 0.005" jam is so I could do a very mild fire form and get headspace correct. Just appeared to work pretty good. Will be trying that again, as well as, 0.010-0.030" jump.
     
  7. 338 Mollett

    338 Mollett

    Joined:
    Sep 2, 2013
    Messages:
    700
    Wade I tried the 197,s and the 195,s and could not get them to shoot well enough to take to a match. I tried them in a 8.75 twist and a 8.25 . Regards Ralph
     
  8. Grimstod

    Grimstod

    Joined:
    Jan 23, 2014
    Messages:
    1,316
    Sierra does recommend a 1;75 twist for this bullet. Are they just being overly conservative?
     
  9. Joe R

    Joe R Please don't send me PMs, I prefer e-mail Gold $$ Contributor

    Joined:
    Feb 4, 2013
    Messages:
    1,453

    I tested the Berger 195s EOL and the Sierra 197s in my 7SAUM. Here's some data on the 197s.


    Capture 8.JPG
     
    Last edited: Sep 1, 2017
    Zero333 likes this.
  10. kyreloader

    kyreloader Gold $$ Contributor

    Joined:
    Dec 24, 2009
    Messages:
    723
  11. Kiwi Greg

    Kiwi Greg

    Joined:
    Jun 3, 2010
    Messages:
    33
    .284
     
  12. kvd

    kvd Silver $$ Contributor

    Joined:
    Aug 13, 2011
    Messages:
    162
    Hi Joe,

    Thank you for sharing the data on the 197's. Could you elaborate on what your measurements of BBTO:, Lands:, and Bore Polished at: number are referring to.

    May give these bullets a try in my 7SAUM.

    Ken
     
  13. Joe R

    Joe R Please don't send me PMs, I prefer e-mail Gold $$ Contributor

    Joined:
    Feb 4, 2013
    Messages:
    1,453
    BBTO = Bullet Base To Ogive. I sort my bullets that way.
    Lands = Using a Hornady OAL gauge I measure where the bullet touches the lands.
    Lands - CBTO = Jump 2.359-2.347= .012
    Bore Polished = How many rounds through the barrel when I polished the bore last with Iosso

    The number inside the diamond refers to grains of powder. The numbers next to the diamond refer to:
    1. Average muzzle velocity
    2. Standard Deviation
    3. Extreme Spread
    4. Number of Rounds

    So for the second target I used 63.0 grains of H-1000 and they had an average muzzle velocity of 2890 fps, standard deviation of 11.5 fps, an extreme spread of 28 fps and I fired 5 rounds on that target.
     
    kvd likes this.
  14. kyreloader

    kyreloader Gold $$ Contributor

    Joined:
    Dec 24, 2009
    Messages:
    723
    Sorry Joe, what caliber is this for, 7RSAUM?
     
  15. Joe R

    Joe R Please don't send me PMs, I prefer e-mail Gold $$ Contributor

    Joined:
    Feb 4, 2013
    Messages:
    1,453
    Yes, you are correct. I had corrected my original post when you asked and inserted it just above the picture, I guess its too easy to overlook.

    Joe
     
  16. kvd

    kvd Silver $$ Contributor

    Joined:
    Aug 13, 2011
    Messages:
    162
    Appreciate the clarification. I cogitated on your post for a while but just couldn’t decipher the numbers on my own. Glad I ask because this is useful information.

    Hope all is well for you in the Houston, TX area.

    Ken
     
  17. kyreloader

    kyreloader Gold $$ Contributor

    Joined:
    Dec 24, 2009
    Messages:
    723
    Joe and others, if you have shot 180s in the same barrels that you are shooting 197s, how much have you had to drop your load to avoid pressure?

    Looking at some calculators, it appears that 1.5-2g should be safe/normal.

    Thoughts?
     
  18. Joe R

    Joe R Please don't send me PMs, I prefer e-mail Gold $$ Contributor

    Joined:
    Feb 4, 2013
    Messages:
    1,453
    kyreloader,
    No, I haven't shot the 180 hybrids in the same barrel that I've used the B195s and S197s. You have to have a lot of freebore to shoot those two bullets and that make's it difficult to shoot the 180s because they would have to jump a whole lot. I don't have much experience with jumping more than .020+ so I'm reluctant to deal with it.

    Joe
     
  19. Ackley Kid

    Ackley Kid

    Joined:
    Mar 16, 2014
    Messages:
    19
    How much free bore are you guys running for the S197gr ?
     
  20. kyreloader

    kyreloader Gold $$ Contributor

    Joined:
    Dec 24, 2009
    Messages:
    723
    Joe, asking the question a different way, your target above is shooting between 62 and 65g of powder, any idea what the same test would be with your 7RSAUM if you were shooting it with the 180g class bullet (irrespective of the freebore and set up)? So you will likely settle between 63-64g of powder with the 197s, any idea where most settle with same powder shooting the 180s?
     

Share This Page