bullet stability

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by drpbroun5, Mar 31, 2015.


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  1. drpbroun5

    drpbroun5 Well-Known Member

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    How do I tell for certain if a bullet is stable or not? I am starting to work up a load for my 300 Win Mag. It has a fairly slow twist at 1 in 10 3/4". I'm told by the custom rifle maker that it will stablize a bullet up to and including a 215gr Berger. I know Bryan Litz's recommendation. I have loaded one ladder test done at 100 yards with H1000 from 75.0gr to 80.5gr in 0.5 increments with one round per charge. All of the holes in the target at 100 yards were round I only found one node that was +/-0.5gr. Since all of them were round, I think that the bullet is stable inspite of it being a marginal twist rate. Am I thinking correctly? I greatly appreciate your thoughts.
    Thank you.
    Paul
     
  2. wbm

    wbm Well-Known Member

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    Move to 300 yards.
     
  3. snox801

    snox801 Well-Known Member

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    Bingo 300 will tell you what you want.
     
  4. Canadian Bushman

    Canadian Bushman Well-Known Member

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    Your bullet will be marginally stable.

    What i mean is your bullet will hit pointy end first, even way out there but your BC is gonna be sacrificed a bit from the less than required twist your using.

    Twist Rate Stability Calculator | Berger Bullets

    Ive tested some of the predictions of this calculator and found it to be pretty accurate.
     
  5. BryanLitz

    BryanLitz <b>Official LRH Sponsor</b>

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    wbm and snox801,

    What do you think will happen at 300 that's not evident at 100?

    My answer to the OP is based in what the Berger calculator linked above will say.

    Basically I think your accuracy will be good with the 215's in a 1:10.75" twist, but you'll be leaving some BC on the table in most conditions.

    -Bryan
     
  6. Rockfish Dave

    Rockfish Dave Well-Known Member

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    I have a spreadsheet for calculating bullet stability. It is a calculator for a project I was working on.

    PM me your email and I'll send it to you. Pretty self explanatory. Just update the yellow fields with your information and it will tell you what the stability factor is for your given input.
     
  7. drpbroun5

    drpbroun5 Well-Known Member

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    Dave,
    PM sent. Thanks.
     
  8. drpbroun5

    drpbroun5 Well-Known Member

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    Bryan,
    Which Berger bullet do you think will give me the best flight characteristics ( terminal BC, wind effects, etc) and the best energy at 1000(+) yards to use for elk hunting, considering the twist rate in my 300 Win Mag (1 in 10 3/4")? I read a thread on this site by BROZ evaluating the Berger 215 Hybrid in his 300WM. That is what convinced me to start with it for bullet selection. My custom rifle maker told me that my rifle will stabilize the 215 and thought it would be an excellent elk round. He recommended a 208 AMax for deer. I will hut both with my final load. I just what the most effective terminal ballistics at range. I will greatly appreciate any recommendations for you and your thoughts. Thank you!
    Paul
     
  9. FEENIX

    FEENIX Well-Known Member LRH Team Member

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    Paul,

    Jeff (BROZ) did an awesome job evaluating the 215s and obviously yielded very good results.

    I think your current set-up would be fine with the 215s esp. if/when you're going after MT elk.:D

    Do a custom search on the top right corner on MontanaMarine's post stabilizing them 215s off his .308 Win (1:12" IIRC ) ... Montana's elevation does wonders on them high BC Bergers.lightbulbgun)

    Cheers!

    Ed
     
  10. drpbroun5

    drpbroun5 Well-Known Member

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    I have applied for a combo license for elk and deer in Montana for this fall. I also applied for an elk special area permit. I plan to hunt both species. This is why I'm trying to work up a good load for my 300 WM with a good bullet for both. BROZ's post a couple of years ago about the 215 Hybrid convinced me to try it first. I'm concerned though after Bryan Litz's post on the loss of BC. Hopefully he will answer my question on this thread. Obviously I am considering what the trajectory will be, how well it handles the wind, and terminal energy at range (out to 1000+). I would try smaller bullets if they fly better and perform better down range. Prior to seeing BROZ's post I was going to start with Berger's 210VLD and even drop back to their 190 if necessay. I want the most retained total energy when the bullet touches hide at range. I think the 215 is stable out of my rifle becauce all of the holes in my target are round at 100 yards. I'm not sure of that though, thus I started this question. Some on the thread suggested going to 300 yards, but Litz's question makes me wonder if that is necessary. I can shoot out to 200 yards at my local gun club, but it takes a one hour drive for me to get to a range that allows longer shots (400 yd at that one). I am more concerned with terminal ballistics on game along with precision and accuracy than I am with muzzle velocity. I greatly appreciate everyone's comments and invite more. Thank you!
    Semper Fi!
    Paul
     
  11. FEENIX

    FEENIX Well-Known Member LRH Team Member

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    Paul,

    Try changing the altitude from where you and Montana using this Twist Rate Stability Calculator | Berger Bullets and you'll be surprise what the difference of SG is.

    My SAKO M995 is 1:11" , I live ~3300' and hunt between 5000-7500' ... you'll be just fine with the 215s.

    Ed
     
    Last edited: Apr 1, 2015
  12. drpbroun5

    drpbroun5 Well-Known Member

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    Bryan Litz,

    Please give me you thoughts on this question about the best Berger bullet that you think will fit my needs for hunting elk. Thank you!

    Regards,
    Paul
     
  13. BryanLitz

    BryanLitz <b>Official LRH Sponsor</b>

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    Paul,

    Even if not fully stabilized, I still think the 215 Hybrid is a great option for your application. Having said that, there's a good chance your 1:10.75" twist barrel will fully stabilize the bullet if your altitude is high enough.

    Ideally you want SG (stability factor) to be 1.5+ to get all the BC from the bullet. However, if SG is lower than 1.5, you'll still have good precision and accuracy, just a compromised BC; about 3% per 0.1 of SG.

    At sea level, your SG will be roughly 1.25, and your BC about 7% lower than it can be. At 3000 feet ASL, your SG will be about 1.4; almost fully stable and BC about 3% lower than it can be. At around 4500 feet altitude, your SG reaches 1.5 and BC is maximized.

    It's very common for SG's to be under 1.5 especially with modern long bullets so it's not a real big deal to worry about.

    My suggestion is to work up a good load with the 215's at 100 yards. Then take it out to long range and practice ranging, calculating drop, and shooting at many targets. This will build the skills you need and will tell you if you need to look for another bullet or not.

    Good luck,
    -Bryan
     
  14. BEEMAN

    BEEMAN Well-Known Member

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    80 gr of H1000 is a lot. Any pressure signs? What kind of speed did you get with 80 gr? My 300 WM with Nosler brass is near max with 79 gr H1000. Running 3000 fps with a 215 out of a 26" Brux. The 215 is one of the nicest bullets I have tried. Very forgiving and easy to load develop.