6.5mm keyhole at 500 yds.

[liltank]

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

 

[markb1951]

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

 

[liltank]

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

 

[MontanaRifleman]

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?

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.

 

[Tyler Kemp]

If you're hitting a small target at 500 yards, I doubt stability is an issue.

 

[elkaholic]

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

 

[MontanaRifleman]

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.

 

[MontanaRifleman]

This is VERY common; especially with bullets that don't expand. This is very typical with the smk's.........Rich

Rich, would you say this was more common for the long, high BC bullets which require greater SF's?

I've also read a number of posts describing pencil holes made by SMK's, Bergers and TSX's that didn't expand.

 

[elkaholic]

Rich, would you say this was more common for the long, high BC bullets which require greater SF's?

I've also read a number of posts describing pencil holes made by SMK's, Bergers and TSX's that didn't expand.

That has been my experience. I think once the bullet ogive is turned slightly without expanding, it tends to steer the bullet that direction like a rudder. At the velocities they are traveling, it doesn't take much to swap ends, especially when twist is a little lacking. I have often seen unexpanded bullets do this in water tests. It seems when the bullet expands quickly, they tend to tumble less. I've always assumed that it is at least partly because a mushroomed bullet will have more weight forward which tends to keep the front end in the lead. Thats my theory and I'm stickin to it! The SMK's are famous for it......Rich

 

[liltank]

Not to sound like a conspiracy theorist here, but I watched a documentary on the History channel where they replicated the shot made on Kennedy with the same exact bullet, rifle, height of shot, and distance. It proves the banana effect and trajectory stabilization theory. Quite interesting if you get to see it.

Tank

 

[markb1951]

Is OK for what application? Paper punching or hunting? How long are the Scenar 123's?



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.

The length of the 123 gr. Scenar is 1.303". Another bit of information is the hollow point is very small. I poked a small diameter wire in and found that from the bullet tip to the lead inside the jacket it's almost .5".

The result of the calculation done by JBM is 1.72.

So far just paper punching but I will need a reliable expanding bullet for deer hunting.

 

[MontanaRifleman]

The length of the 123 gr. Scenar is 1.303". Another bit of information is the hollow point is very small. I poked a small diameter wire in and found that from the bullet tip to the lead inside the jacket it's almost .5".

The result of the calculation done by JBM is 1.72.

So far just paper punching but I will need a reliable expanding bullet for deer hunting.

Interesting... That SF should be fine. The GS SF's do assume expansion, so maybe the non-expanding bullets have a greater tendency to swap ends on contact... the CG being to the aft of the bullet.

Have you considered the 130 Sciroccos? They are on my short list for a 6.5 plinking and hunting bullet. I've also asked GS to design a 6.5 LR bullet as well.