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6.5mm keyhole at 500 yds.

 
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  #15  
Old 03-26-2011, 01:38 PM
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Location: Central Pennsylvania
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Re: 6.5mm keyhole at 500 yds.

JBM ballistics has a trajectory card you can input a bunch of variables to include barrel twist, and bullet length. When you hit calculate to make your range card, it gives you the stability factor. Here is a link to the page you need to do that.

JBM - Calculations - Trajectory (Drift)

Put in all the info, and let it do its thing. Once the range card comes up, you will see all the info you put in, plus the PBR, and stability factor. Not to mention you will have a range card.

As for bullets, my choice is the 123, 140SMK, and 140 BTHP, SST, A-max, 123 A-max, or the 129 SST. I'm thinking 123SMK if and when I ever get my 6.5x47Lapua built.

Tank
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  #16  
Old 03-26-2011, 02:52 PM
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Re: 6.5mm keyhole at 500 yds.

Quote:
Originally Posted by liltank View Post
JBM ballistics has a trajectory card you can input a bunch of variables to include barrel twist, and bullet length. When you hit calculate to make your range card, it gives you the stability factor. Here is a link to the page you need to do that.

JBM - Calculations - Trajectory (Drift)

Put in all the info, and let it do its thing. Once the range card comes up, you will see all the info you put in, plus the PBR, and stability factor. Not to mention you will have a range card.

As for bullets, my choice is the 123, 140SMK, and 140 BTHP, SST, A-max, 123 A-max, or the 129 SST. I'm thinking 123SMK if and when I ever get my 6.5x47Lapua built.

Tank
I used their Stability calculation and 1 to 8 is OK. Stability according to JBM is not an issue until you get to 1 to 9.5 twist.

When it comes to bullets I think the next choices are 123SMK, 123 AMAX, 129 SST, and 130 Berger.

Thanks for your input.
Mark
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  #17  
Old 03-26-2011, 03:52 PM
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Re: 6.5mm keyhole at 500 yds.

Anything above 1.0 is optimum. The higher the number the better off you are. A lot of guys are having good luck with the Bergers. I'm a bit of a tight wad, so I prefer the Sierra's and Hornady's.

Tank
__________________
Matthew 7:13-14
"Enter through the narrow gate. For wide is the gate and broad is the road that leads to destruction, and many enter through it. [14] But small is the gate and narrow the road that leads to life, and only a few find it.

If you find your self in a fair fight, your tactics suck!- Marine 1st Sergeant Jim Ryfinger

Friends don't let friends develop canonitis!-chucknbach

arguing over the internet is like the special Olympics....even if you win, you are still...special!
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  #18  
Old 03-26-2011, 04:03 PM
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Re: 6.5mm keyhole at 500 yds.

Quote:
Originally Posted by markb1951 View Post
I used their Stability calculation and 1 to 8 is OK. Stability according to JBM is not an issue until you get to 1 to 9.5 twist.
Is OK for what application? Paper punching or hunting? How long are the Scenar 123's?

Quote:
Quote:
Originally Posted by liltank View Post
Anything above 1.0 is optimum. The higher the number the better off you are. A lot of guys are having good luck with the Bergers. I'm a bit of a tight wad, so I prefer the Sierra's and Hornady's.

Tank
GS recommends a minimum of 1.1 for their bullets and 1.4 for general hunting shorter than 500m, and 1.6 for dangerous game and brush.

A stability factor of 1 is basically on the edge of stability.
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  #19  
Old 03-26-2011, 06:18 PM
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Re: 6.5mm keyhole at 500 yds.

If you're hitting a small target at 500 yards, I doubt stability is an issue.
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  #20  
Old 03-26-2011, 06:54 PM
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Re: 6.5mm keyhole at 500 yds.

Quote:
Originally Posted by markb1951 View Post
I have begun shooting at extended ranges a short time ago and experienced an unusual happening. Some background to explain, caliber is 6.5x284, 24" barrel 1 in 8 twist, Lapua brass, Lapua Scenar 123 gr., 2975 FPS muzzle velocity, target was at 503 yds. The target was a 2 liter plastic pop bottle filled with water with a 2' by 3' piece of ceiling tile placed 12" behind the bottle. The bullet entered the bottle with a round hole and left with a triangular hole, no explosion of the bottle, only holes front and rear. It then entered the tile at 90 degrees leaving a hole that the bullet will lay in. Any ideas?
This is VERY common; especially with bullets that don't expand. This is very typical with the smk's.........Rich
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  #21  
Old 03-26-2011, 07:27 PM
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Re: 6.5mm keyhole at 500 yds.

Quote:
Quote:
Originally Posted by Tyler Kemp View Post
If you're hitting a small target at 500 yards, I doubt stability is an issue.
You're right... that 's why I asked what the "application" was. And I assume what you mean by a small target is something like a coyote or smaller. Some hunt elk with the 6.5's.
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