New #2231 200gr SMK for F/TR

Discussion in 'Big Stuff -- 6.5mm, 7mm, 30 Cal' started by Quickoz, Jan 18, 2018.

  1. Archer

    Archer

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    yes, I have adjusted my seating depth to .009 off the lands with .002 neck tension. the powder charge is the same at 43.5 gn producing an average velocity of 2608 fps. shooting very well.
     
  2. Ilya S.

    Ilya S.

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    10x for sharing;) Whats the real confirmed g7 bc ? 0.339 like Ned Ludd says or more ?
    Before ordering 9tw tube, I wanna table some ballistic data to compare with 200.20..
     
  3. Eternal Student

    Eternal Student

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    What if it's longer? Twist needed is dictated by length more than weight. Flat Line has a 198 gr. 30 cal projectile that is longer than my 215s/230s and it requires a 9 twist.
     
  4. joshb

    joshb Gold $$ Contributor

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    Bump.
     
  5. Down South

    Down South FTR Junkie Gold $$ Contributor

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    I have one here (198 gr Flatline bullet) that was sent to me, don't remember the OAL measurement off hand but it's a lot longer than the Berger 230 hybrid if I remember correctly. It's definatley a super long sleek looking bullet. I personally would run a 8 twist with a bullet that long, especially at .308 speeds.
     
    Eternal Student likes this.
  6. paulT

    paulT

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    Wondering for FTR In a .308 would an 8 twist give optimum stability with the 2231 sierra also allowing to shoot berger 20x and 185g hybrid or would an 8 twist be too fast for the latter 2 bullets.
     
  7. Down South

    Down South FTR Junkie Gold $$ Contributor

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    Definately not neccessary with 185s, X bullet or 200 gr Sierra bullet but i'm sure it would work. I've shot and so have many others 155s with 10 twist barrels with great results so why wouldn't 8 twist work with longer heavier bullets? With that said, i'd go with a straight 9 twist barrel for those 3 bullets listed and not look back. I currently have a 30 inch 9 twist barrel on one of my FTR guns and it absolutely loves X bullets. I shot that load at the Texas LR Championship this year and it shot great.
     
  8. Ned Ludd

    Ned Ludd Silver $$ Contributor

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    If you want to assess and compare twist rates for different bullets, all you need to do is plug in the bullet OALs/BCs with the appropriate atmospheric inputs here:
    http://www.bergerbullets.com/twist-rate-calculator/

    There are potential issues with running much faster-than-necessary twist rates, including effects on accuracy and possible jacket failure. The question here is whether an 8-twist is too fast at twist rate for some of the 185/200 gr 30 cal bullets currently being used in F-TR at the 2650+ fps velocities typically seen with 30"+ barrels. As Jade mentioned, 9-twist barrels seem to be working just fine for some of the 200 gr bullets currently available. I've also personally shot many bullets in the 190-ish gr weight range in commercial loads from a short (16") 8-twist 30 cal barrel at somewhat lower velocities without any issues, but that's not really the same thing. Only way to know for sure is to have an 8-twist pipe chambered and try it. If they shoot as well as from barrels with more optimal twist rates (9.5- to 10.5-twist range), you're GTG. If they don't work well, then you have an expensive tomato stake.

    Having played around with several different 30 cal bullets this year in the 200-210 gr weight range, my take is that they're all close enough in terms of BC that none is going to enjoy any "quantum leap" advantage over the other. So if the BCs are all pretty close, what it really boils down to for me is how easy a particular bullet is to tune, how consistent the precision is, and how well you can handle the recoil. In my hands, the 200-20X bullet was probably the most consistent in terms of the first two considerations. They are pretty easy to tune and very consistent on the target. I personally find that pushing any 200 gr bullet out of an 18 lb F-TR rifle at 2650+ fps is about all the recoil I can manage. If I am not 100% on top of it at every second, I will start seeing vertical issues. YMMV.

    There are several 30 cal bullet choices that fall into this particular class of bullets for F-TR (i.e. 200+ gr, G7 BCs > .315) that all have the potential to win. They're all close enough in BC that none is a huge advantage over the other in terms of wind deflection. So in the end, I think what it really boils down to is consistency on the target and how easy they are for an individual to tune in.
     
    PGS, Down South, Laurie and 1 other person like this.
  9. Jdne5b

    Jdne5b Gold $$ Contributor

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    We use an 8 twist for a 220gr Subsonic bullet in Blackout. Its plenty stable. I dont see a need to go that fast at >2× the speed. For reference, the 215 hybrid is 1.6sg in my blackout.

    An 8tw at 2600 for the 20x bullet is an Sg of 2.4 fwiw.
     
  10. Pinkes

    Pinkes

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    Any new update on this bullet? or BC maybe?

    Also looking to try a few...
     

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