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  #11  
Old 03-01-2020, 03:41 AM
jim barker jim barker is offline
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Hate that you have to go through this, but its just going to get worse.
Ever think about relocating?
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  #12  
Old 03-01-2020, 05:33 AM
georgeld georgeld is offline
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I'v never played with the lead free stuff.

I did try to shoot 35gr V/max in a .223.
They're mighty short and flew into one hole at 100yds.
14" twist.
Just beyond 200yds they went wild all over the hillside.

Whether this relates to your problem or not I have no idea.

good luck and show us the pattern they make for you.
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  #13  
Old 03-01-2020, 01:25 PM
Bayou City Boy Bayou City Boy is offline
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Quote:
Originally Posted by elalto View Post
Thank you all for your responses!

BCB, I think you are right on and I tend to believe that the bearing surface length has little to do with bullet stability.

I have decided to experiment with the 55grn bullets that I have (Nosler BT). I shortened some today and loaded them up exactly as I do the 60grn lead core Sierra HP bullets that shoot so well in my rifle. I cut the bullets in my mill so that they are exactly .7320" (as the Sierra's) from the original .950" (of the Nosler's).



The only question I have now is that after cutting the tip off the bullet I have a large "hollow point" what do you all think this may do to bullet flight and the poor coyote at the receiving end??



Thank you all,
Marcos (elalto)
If cutting the tips off does not affect core stability of the bullets when the bullets are fired, they should work fine.

Obviously the BC of the bullets will be affected significantly which might affect longer range performance (200-250+ yards). You'll only know to what extent by shooting them at extended ranges.

-BCB
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  #14  
Old 03-02-2020, 01:27 PM
AWS AWS is offline
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There is a very old but still relevant formula for determining the appropriate bullet for the twist, it is called the Greenhill Formula. I was developed mainly for cannons but works for out tiny cannons also. It is based on length and not weight.

I doubt that turning off the tip is going to have much effect on terminal performance on coyotes, it does change the BC on the bullet but under a couple hundred yards it shouldn't make that much difference there either.

There is really only one way to tell, shoot some coyotes with them there isn't a armchair theorist I the world that can answer that question better than you shooting them. You might want to try and just pull the plastic tip and see if that helps.

I wish I could be of more help, I love the 55gr NBT LF's in my 6mm-204 and 6x45 for hunting in LF areas.
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  #15  
Old 03-02-2020, 03:00 PM
Bayou City Boy Bayou City Boy is offline
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Good post, AWS.

The Greenhill Formula is an old but still viable approach for determining proper barrel twist rates. As you state it was originally designed for artillery projectiles.

The Miller rule is a mathematical attempt to improve on the Greenhill Formula and it has become more widely used in our "more modern" times for much smaller rifle bullets.

Both widely accepted ideas/methods use projectile length for determining proper barrel twist rates and how much twist rate it will take to stabilize a cylindrical shaped bullet once it clears a rifle barrel.

Without a doubt, any time that you alter some existing item, like a bullet in this case, the only way to know what effect the alteration has is to try it in a "live" environment. Anything less is just speculation. Hopefully elato will cause some of his altered bullets to collide with a coyote or two.

-BCB
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Last edited by Bayou City Boy; 03-02-2020 at 03:04 PM. Reason: line spacing...................
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  #16  
Old 03-02-2020, 03:50 PM
Johnly Johnly is offline
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Ran some stability calculations for the 55 gr. Nosler Lead Free with the following results:

Stability Input Data
Caliber: 0.243 in Bullet Weight: 55.0 gr
Bullet Length: 0.945 in Plastic Tip Length: 0.200 in
Muzzle Velocity: 3300.0 ft/s Barrel Twist: 14.0 in
Temperature: 59.0 °F Pressure: 29.92 in Hg
Output Data
Stability: 0.905

02-Mar-20 09:43,
JBM/jbmstab-5.1.cgi

Stability Input Data
Caliber: 0.243 in Bullet Weight: 55.0 gr
Bullet Length: 0.945 in Plastic Tip Length: 0.200 in
Muzzle Velocity: 3300.0 ft/s Barrel Twist: 13.0 in
Temperature: 59.0 °F Pressure: 29.92 in Hg
Output Data
Stability: 1.049
02-Mar-20 09:45,
JBM/jbmstab-5.1.cgi

Stability Input Data
Caliber: 0.243 in Bullet Weight: 55.0 gr
Bullet Length: 0.945 in Plastic Tip Length: 0.200 in
Muzzle Velocity: 3300.0 ft/s Barrel Twist: 12.0 in
Temperature: 59.0 °F Pressure: 29.92 in Hg
Output Data
Stability: 1.232
02-Mar-20 09:46,
JBM/jbmstab-5.1.cgi

I'm really suspecting that the barrel twist is slower than 1/12 based on these results.
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  #17  
Old 03-02-2020, 06:25 PM
elalto elalto is offline
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Johnly, you could be right.

Using the cleaning rod method, I have measured something between 12 and 13 inches per rev. The gunsmith that put together my rifle was a very highly ranked competitor and 6X47 was his competition caliber. He used one of his "custom" ordered Douglas Air Gauged barrels for my rifle. Until now, I have never used anything but the 60grn Sierra HP bullet in the rifle as per his suggestion.

I plan to try my altered 55grn NTB's at the range tomorrow so I will know how they shoot. If they shoot well, I will try to get out in the next few weeks and see how they do on a varmint.

Marcos (elalto)
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  #18  
Old 03-03-2020, 08:00 PM
elalto elalto is offline
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Default Problem SOLVED!!!

Hi All,

Went to the range this morning and shot the "cut down" 55grn Nosler BT bullets.

First, I fired a 5 shot group with the 60grn Sierra HP that have always shot so well in my rifle then, I let the barrel cool down while playing with a couple other rifles. Unfortunately, the wind came up by the time I was ready to shoot the "altered" Nosler's so the group was not as good and I pulled one shot left BUT they shot WELL.

So I just have to "trim" my bullets and load them up! I will try to find out how they do on a coyote but will not be able to compare unless I get a chance to get out to Arizona. Below is the target from this morning, I can be satisfied with this..

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