6.5mm keyhole at 500 yds.

[markb1951]

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?

 

[liltank]

Sounds like a normal reaction to me. Anytime a bullets path is altered in any way i.e.: water, tree, bottles, etc. you cause the bullet to loose energy in its flight path causing cavitation. This cavitation is what causes some bullets to tumble through animals and targets after impact rather than passing through unchanged. Depending on the construction of the bullet will also effect the flight of the bullet. An example would be a FMJ vs a SGK. The FMJ is designed to maintain its shape when penetrating an object, whereby a soft point bullet such as the SGK is made to deform. The reason you got a hole in side 1, is due to the fact it was at its optimum performance. Side 2 with the triangle you started seeing the effect of the bullet coming apart or deforming. The target is a result of lost performance of the bullet entering the bottle, losing momentum in the water and penetrating the rear surface and then hitting the tile. That is about as simple a terms as I can hypothesize and use the little bit of knowledge on physics that I can give you. As far as the bottle not exploding, if it is not filled to the very top where pressure will have no where to go, then it will more than likely pass through with no explosion and a couple holes. These are only my thoughts, but pretty sure I'm on track.


Tank

 

[Gene Jr.]

I don't see anything strange there at all. The water will certainly cause the bullet to lose stability and start to tumble. It's cool you captured it with the backer. gun)

 

[liltank]

Scenar's are known for not opening up either.

Tank

 

[markb1951]

Liltank, I guess my experiences (at shorter ranges) the destruction of the bottle is complete. The Scenar jacket must be very tough. My plan is to use the rifle for deer hunting, so it looks like Scenars are out. Anybody have any recommendations on a bullet in the 120 - 130 gr. range to use? Nosler Ballistic Tip, Berger, and Hornady SST will be the next choices.

 

[MontanaRifleman]

It was simply under stabilized for terminal penetration. A well stabilized bullet would have continued in a straight path.

-Mark

 

[markb1951]

It was simply under stabilized for terminal penetration. A well stabilized bullet would have continued in a straight path.

-Mark

Do you think that 1 in 8 twist should have stabilized the bullet, or am I missing something?

 

[royinidaho]

Scenar's are known for not opening up either.

Tank

Roger that!!!

 

[MontanaRifleman]

Do you think that 1 in 8 twist should have stabilized the bullet, or am I missing something?

One would think the 8 twist would be sufficient.

The Stability Factor (SF) for a bullet to maintain stable flight for general shooting and paper punching is lower the the SF required for terminal penetration.

 

[scottmilk9]

I think you should perform another test. Shoot the ceiling tile without anything in front of it. I be you will only have a hole there. Once the bullet goes through the jug of water it probably loses enough energy/velocity that it becomes unstable.

I am surprised that the water jug didn't blow apart though. Did you have a cap on it or was it open?

Good luck.

Scott

 

[markb1951]

I think you should perform another test. Shoot the ceiling tile without anything in front of it. I be you will only have a hole there. Once the bullet goes through the jug of water it probably loses enough energy/velocity that it becomes unstable.

I am surprised that the water jug didn't blow apart though. Did you have a cap on it or was it open?

Good luck.

Scott

I have shot the ceiling tile before using it as target backing and it showed a nice hole.

The jug was capped and full to within an inch.

Still have no idea why the jug didn't open up.

 

[markb1951]

One would think the 8 twist would be sufficient.

The Stability Factor (SF) for a bullet to maintain stable flight for general shooting and paper punching is lower the the SF required for terminal penetration.

Thanks for the heads up on SF. Is there any reading material available to further my education?

 

[MontanaRifleman]

I think you should perform another test. Shoot the ceiling tile without anything in front of it. I be you will only have a hole there. Once the bullet goes through the jug of water it probably loses enough energy/velocity that it becomes unstable.

I am surprised that the water jug didn't blow apart though. Did you have a cap on it or was it open?

Good luck.

Scott

A bullet's KE really doesn't have anything to do with stability. And once the bullet leaves the muzzle, the slower it gets as it goes down range, the more stable it becomes. The reason is that the bullet's rate of spin remains constant as it slows down. It would actually have a better chance of penetrating in a straight path @ 1000 yds vs 500.

 

[MontanaRifleman]

Thanks for the heads up on SF. Is there any reading material available to further my education?

You could do a net search on the subject... I learned this from conversations with the makers of GS Custom bullets. They list required SF's for their bullets based on application.

GS CUSTOM BULLETS - Specifications for use