150 SMKs and the 6.5 x 284 ***UPDATE***

Discussion in 'Big Stuff -- 6.5mm, 7mm, 30 Cal' started by ShootDots, Jan 31, 2018.

  1. ShootDots

    ShootDots Gold $$ Contributor

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    Well a few weeks ago I got my barrel. It is a Krieger, 1-7.5 twist, 4 groove "conventional" rifling, finished at 30". I had it chambered in 6.5 x 284 with a "substantial" freebore to handle the new 150s. I started using H1000 and went from 54.0 to 55.5grs, however the accuracy was somewhat less than what I anticipated. Velocity was from 2950 to 3030 with ZERO pressure signs. BUT whew the accuracy was not good. I then decided to open up the freebore some more. Additionally, I spoke with my "old" riflesmith in Houston, who has extensive experience with the new Hornady 147 ELD-M and some experience with the 150 SMKs. He stated that the node is in the "lower 2900s"..

    Not wanting to go SUPER low with H1000 I decided to go to a faster powder. After much consideration, I settled on RL-23 and went from 47.3grs to 49.0gr to go from the Mid-2800s to the Mid-2900s. There is NO information on HOW to do that, so I extrapolated known load data from H4831sc, which is a bit slower that RL-23 but in the same ball park. Fortunately, I landed exactly where I wanted to be. The loads went from 2850 to 2960! Well Omar was correct and at 2930f.p.s. it looked promising. So today 1-31-2018, I took a load of 48.6grs out to do a ladder test of seating depths. I went from 7 thousandths INTO the lands to 24 thousandths OFF the lands. At 17 off it shot just under an inch at 300 yards in 10m.p.h. winds! SUCCESS!!! >>> Not so fast!

    My last 5 shot group only showed 3 shots on target. I thought "well at 300 yards, I suppose it COULD have 3 bullets in one tiny hole!" However, upon inspection, there were only 3 holes in the paper! Uh OH! I looked at the other bullet holes. Those in the 1-15 shots were clean like a paper punch. However, shots 16-25 had GRAY "lead appearing" marks just a shade below the bullet holes, which were NOT "paper punch pretty"! They were "wallowed out" in appearance! No doubt, those bullets were blowing up upon impact with the foam board backed target paper and the 2 missing had blown up PRIOR to target impact! I called up Sierra and they are now in the process of an investigation. They stated they would get back with me and had me write an email with all of the pertinent info in it.

    My best guess: a 1-7.5, although recommended by Sierra, is too fast for velocities well over 2900. AND the "conventional rifling" I have, instead of some 5R offering, is a bit "aggressive" for that projectile. Back to the drawing board!
     
    Last edited: Jan 31, 2018
  2. nakneker

    nakneker Gold $$ Contributor

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    Well I was all excited till the third paragraph. Do update us when you get some feedback.
     
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  3. ShootDots

    ShootDots Gold $$ Contributor

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    I just ordered a "straight" 8 twist... This 7.5 barrel is an excellent barrel>>>but for me at least, unusable..
     
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  4. whatwind?

    whatwind? Silver $$ Contributor

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    Great info, thanks

    Are you at sea level, think atmosphere has any effect on the results?
     
  5. ShootDots

    ShootDots Gold $$ Contributor

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    No Sir.. I am in Arizona and I shoot at about 1500 ft. ABOVE sea level. And the humidity is nigh on to nothing..
     
  6. HPMike800

    HPMike800

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    Why not try them in your 260 AI?
     
  7. ShootDots

    ShootDots Gold $$ Contributor

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    I tried it in one of my old .260A.I.s.. I did not push it to it's limits but I was near top end with RL-16. I could only get 2820. If I wanted to get to 2930 I would have to push the limits of the strength of the Palma brass. I am not one to push any limits. I like to be 1.5grs. or so UNDER a max load. It is easier to get something with more horsepower and run it at "normal" pressures than to run the limits of a lot smaller case.. That's just me..
     
  8. Sniper338

    Sniper338 Silver $$ Contributor

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    You got plenty. barrel to cut off and rechamber to something else dont you? so its not a complete waste?
     
  9. ShootDots

    ShootDots Gold $$ Contributor

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    Not really.. The chamber end is 1.350">>>not 1.250. That diameter is for 6" and it straight tapers down to 1". I am just at a loss, at this juncture, as to what could be done. I suppose I could have it rechambered to a 6.5 x 47 but, I really want the 150s to work. They have such great potential!
     
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  10. rardoin

    rardoin Silver $$ Contributor

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    I did some preliminary testing in a 6.5 x55 BJAI (30" 8tw 5R Bart.) and was able, with RL-23 to get a charge range that covered from the upper 2800's to the low 3000's but I had no satisfactory groups at 300yds but all target impacts appeared concentric. H1000 did not get me above 2850 fps so I did not test for groups. I did not check H4831 but I will revisit the 150 SMK after the BSWN's. I am testing at near sea level.
     
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  11. ShootDots

    ShootDots Gold $$ Contributor

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    If you can get them doing what you want, you will have an extremely good 1000 yard rifle! I will work at it til I get it right>>> If I can!!
     
  12. FatBoy

    FatBoy

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    You're not at a loss at all. Knock two threads off, re-chamber for 142 SMKs and stop the madness.
     
  13. ShootDots

    ShootDots Gold $$ Contributor

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    Will the 142s stay together at 2950+ with a 7.5 twist when the 150s will not?
     
  14. rardoin

    rardoin Silver $$ Contributor

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    Uhhhh....as much as I don't want to admit it, Chris does have a point:oops:. :D

    I have a very good load at 2960 fps with a PB 142gr so I have been slow on the 150gr bandwagon.

    One of the first (and best) principles I was taught in surgical residency is "The enemy of good...is better!".:rolleyes:
     
  15. ShootDots

    ShootDots Gold $$ Contributor

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    Same question: Will the 142s hold up under the stress of a 7.5 pushing them at 2950-3000 when the 150s are blowing up at 2930?
     
    Last edited: Feb 1, 2018
  16. FatBoy

    FatBoy

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    I don't see why not . I shoot an 8 twist, 4 groove Kreiger at 2980. I know guys running 140 BHs to 3200fps. Of course I can't promise they won't blow up, but if they do my next call would be to Krieger to ask WTF is going on with that barrel.
     
  17. rardoin

    rardoin Silver $$ Contributor

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    Certainly a concern. I don't have a 7.5tw barrel for the 6.5mm. I do have Brux on order though. But, I will continue to test in the 8 twists I currently have.
     
  18. ShootDots

    ShootDots Gold $$ Contributor

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    I have never had a blow-up with an 8 twist either. But add an additional 1/2 twist and many, many thousands more RPM's, and it may be on the horizon. If I do rechamber the barrel it will be with a 6.5 Creedmoor or 6.5 x 47 Lapua and I doubt at 2600-2700 you would get any blow-ups..
     
  19. ShootDots

    ShootDots Gold $$ Contributor

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    There is also the possibility that the "conventional" rifling plays a BIG part in weakening the jackets. A 5R may mitigate that to some degree. But I am not a fan of 5R rifling..
     
  20. Geno C

    Geno C

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    Or wait to see if the new Berger's can handle those rpms before you rechamber.
     
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