Rifle Bullet Performance

Aloysius · Posted: Wed Dec 02, 2009 1:50 am Post subject: Re: Rifle Bullet Performance

Dimitri, I think the british also used wooden tips. When we continue this discussion we might end up by making wooden tips for wadcutters and semi-wadcutters Smile

And it might work. Ever seen a WC shot in a piece of wood? It sure destroys more than a magnum FMJ!

POP!! · Posted: Wed Dec 02, 2009 11:58 am Post subject: Re: Rifle Bullet Performance

I use them all the time! Great bullets and Gerard and Gina are awesome people to work with.

I spent less load-work-up time with these bullets than any others.

gsgroup.co.za/fotis.html

slimjim · Posted: Wed Dec 02, 2009 12:13 pm Post subject: Re: Rifle Bullet Performance

POP!! wrote:

I use them all the time!

What twist is your barrel. I was noticing that one doesn't need near as much twist as with the smaller diameter bullets. Looks like a 1:17 or 1:18 would work fine.

.416 330gr HV

POP!! · Posted: Wed Dec 02, 2009 1:30 pm Post subject: Re: Rifle Bullet Performance

Standard WBY twist. I am at work and can not access their webpage. Sorry.

Dimitri · Super Member Joined: Nov 25, 2005 Posts: 5944

Aloysius wrote:

Dimitri, I think the british also used wooden tips. When we continue this discussion we might end up by making wooden tips for wadcutters and semi-wadcutters Smile

Yes but the packaging of the tip varied in the Mark 7 rounds, from Aluminum, packed paper pulp to Tenite (Thermoplastic made of wood). I have never actually read anything that I trust enough to believe that they used actual wood and not wood based products.

Still when it comes to talking about rifle bullet performance, although his studies focused on military rounds, Martin Fackler is probably the best person to discuss due to his no non-sense scientific view on the subject. All current theories on wounds from gunshots are derived from his experiments.

He showed in his research that the temporary wound cavity of a bullet with high kinetic energy does not actually kill faster then a bullet that produces a larger wound cavity. Yes the M14 with the 7.62mm NATO does kill very effectively, but VN era ball that fragmented produced larger wounds that are more difficult to fix in the battle field or at medical facilitates away from the front.

The 7.62mm NATO ammunition wound profile:

The 5.56mm NATO in the configeration used in Vietnam:

The 5.56mm NATO in Soft Point:

The 5.45mm Russian with a aluminum tip:

Notice how the permanent wound areas are relatively large compared to the 7.62mm NATO round. The 303 British round has a wounding pattern similar to the 5.45mm Russian but with the penetration available with the 308Win.

Dimitri

slimjim · Posted: Fri Dec 04, 2009 7:45 am Post subject: Re: Rifle Bullet Performance

I'm not sure these examples of military bullets really apply to our hunting application. Most of these are full-metal jacket (FMJs). Better wound performance is obtained with FMJs if the bullet tumbles since the FMJ doesn't mushroom to a larger, more effective size as a hunting bullet does. I understood this was one of the problems with the evolution of the M16. Initial model had a slow twist and FMJs tumbled making large wound cavities. To increase accuracy, twist rates got faster and then the FMJs were just leaving pencil holes in their wounded but not terminated targets.

As a hunter, I desire my bullet to expand and stay on course upon entry into the game. I also don't like a lot of meat damage, thus the advantage of an expanding bullet that maintains it weight/integrity. I initially hunted with a .308. The deer I shot never took a step but I always lost the meat of the opposite shoulder. I went to a .243 and eliminated my meat damage but wasn't getting the stopping power I wanted. I believe these issues were caused by improper bullet selection. After a few stumbles last decade when monolithic copper bullets were still new, I believe they have matured to a bullet that reliably expands and maintains their weight. What I feel I'm beginning to understand from the information on GSC's website and other articles there are two aspects to twist rate: one to stabilize the bullet in flight and one to stabilize the bullet after impact. A FMJ benefits from just enough twist to stabilize the bullet in flight. A bullet that maintains its integrity upon impact benefits from additional twist.

I tried to find some simple views that show wound channels to compare to above. The best I found were on the Barnes website. These are not commercials but just high-speed video of gelatin shots that last a few seconds. Check them out if you like.

Wound Channel Videos

Dimitri · Super Member Joined: Nov 25, 2005 Posts: 5944

Biggest reason the M16 lost its ability to stop the enemy as well, is the thicker jackets used for better penetration of hard materials. The jackets breaking apart was the reason they caused such large wounds.

A 308 Win with a soft point, done up by Fackler like above:

As you can see, yes the fact its a SP does play a role in creating a larger wound cavity, however, only the permanent cavity can be considered when attempting to asses the damage the ammunition causes to the animal.

The biggest issue with rifle bullet performance, is that no matter how well you shoot your target, the biological system is a robust one, and what works for one animal may not work at all for another species. Take for example the Vietnam era 5.56mm NATO FMJ, with its wounding abilities, I could go out and shoot a wolf, or other various similar sized animals. And take it down reliably. Hell I could shoot a deer and kill it quickly enough.

However that same ammunition wont work as well as one would like on a moose or medium/large bears. At that point, over all penetration is more important then simply how large the permanent wound cavity is, this is because you still need to get inside of the target and hit something important. GroovyJack knows all about this. Very Happy

Dimitri

slimjim · Posted: Fri Dec 04, 2009 9:12 am Post subject: Re: Rifle Bullet Performance

Dimitri wrote:

over all penetration is more important then simply how large the permanent wound cavity is, this is because you still need to get inside of the target and hit something important.

"Penetration to hit something important" can benefit from a bullet that retains its weight, doesn't fragment, and stays on course during the terminal phase. This is the point GCS is making and the advantage of a monolithic bullet with a faster twist rate than just to stabilize it in the air.

chambered221 · Posted: Fri Dec 04, 2009 3:22 pm Post subject: Re: Rifle Bullet Performance

Regardless the type of bullet, the size of the wound channel, or how much it penetrates the single most important issue is it’s location. But yes there is a minimum amount of permanent damage that is required.

Place it to instantaneously stop circulation of the blood and you’ll have an instantaneous kill.
There are 4 areas that this can be accomplished:
Central nervous system- A hit to the proper region of the brain or the base of the neck.
Heart-At the aorta
Lungs-Area in which the two lungs join the trachea tube

It should be noted that a general hit to these areas do not cause an immediate loss of pressure.
For example blow up a balloon and release it. This represents the classic broadside double lung hit. Blow up the same balloon and pop it with a pin, this will represent a hit where the 2 lungs join the trachea tube.
The same can be said for the heart.
The CNS is a matter of hitting the switch that sends the impulses, otherwise only paralysis occurs.

Aloysius · Posted: Fri Dec 04, 2009 3:36 pm Post subject: Re: Rifle Bullet Performance

I agree. Caliber should not replace bullet placement.
It's only when things don't go as expected that I like a big exit hole very much. But still: better concentrate on the first hit!
I even think that stronger animals can shut down their nervous system when they are hit in a non lethal zone. I have seen wild boars still running till all blood is lost, simply because the first shot didn't kill them and it seemed as he didn't feel the folowing shots anymore.

Dimitri · Super Member Joined: Nov 25, 2005 Posts: 5944

I am not advocating caliber over all else, instead I am advocating comparing them subjectively to cause the most required damage where its required.

Dimitri

tcknight · Posted: Fri Dec 04, 2009 5:15 pm Post subject: Re: Rifle Bullet Performance

Aloysius wrote:

Maybe they can produce custombarrels with that fast twist in SA?
I'm beginning to get some feeling about twist and in my opinion, the faster the better. When a twist is too fast for a certain bullet, one can easely take the speed down till that light bullet also gets stabilized. On the other hand: when a twist is too slow, maximum pressure will limit you when you want to increase the speed of that heavier (or longer) bullet till it stabilizes.

Makes sence?

Some. But you can't just state that out-of-hand because there are many more variables. The problem with a very fast twist for a light-for-calibre bullet is not that you need to slow it down to stabilize it. The main problem is that a jacketed smaller bullet can come apart from over spinning because it is moving faster down the tube than the heavy bullet. For pratical purposes, you can't "over stabilize" a bullet. However, there is a place for a slower twist. The slower the twist rate, the faster you can send the bullet toward target. Pressures will be lower in slower twist so you can speed up the bullet with more powder. I can gain 300 to 400 fps more speed from my 75 grain .243 bullets from my custom made 1:12 twist barrell than from the standard 1:9.25 twist.

tcknight · Posted: Fri Dec 04, 2009 5:26 pm Post subject: Re: Rifle Bullet Performance

chambered221 wrote:

Regardless the type of bullet, the size of the wound channel, or how much it penetrates the single most important issue is it’s location. But yes there is a minimum amount of permanent damage that is required.

Place it to instantaneously stop circulation of the blood and you’ll have an instantaneous kill.
There are 4 areas that this can be accomplished:
Central nervous system- A hit to the proper region of the brain or the base of the neck.
Heart-At the aorta
Lungs-Area in which the two lungs join the trachea tube

It should be noted that a general hit to these areas do not cause an immediate loss of pressure.
For example blow up a balloon and release it. This represents the classic broadside double lung hit. Blow up the same balloon and pop it with a pin, this will represent a hit where the 2 lungs join the trachea tube.
The same can be said for the heart.
The CNS is a matter of hitting the switch that sends the impulses, otherwise only paralysis occurs.

Right on Charlie Brown! Very Happy

Just when I was beginning to think you were nothing but a good ole boy like me, you come up with some kind of intelligent write up like this. Jaw Drop

chambered221 · Posted: Fri Dec 04, 2009 7:03 pm Post subject: Re: Rifle Bullet Performance

Wise tankya TC......them their r some kind werds !!! Laughing

chambered221 · Posted: Fri Dec 04, 2009 8:18 pm Post subject: Re: Rifle Bullet Performance

tcknight wrote:

Aloysius wrote:

Maybe they can produce custombarrels with that fast twist in SA?
I'm beginning to get some feeling about twist and in my opinion, the faster the better. When a twist is too fast for a certain bullet, one can easely take the speed down till that light bullet also gets stabilized. On the other hand: when a twist is too slow, maximum pressure will limit you when you want to increase the speed of that heavier (or longer) bullet till it stabilizes.

Makes sence?

Some. But you can't just state that out-of-hand because there are many more variables. The problem with a very fast twist for a light-for-calibre bullet is not that you need to slow it down to stabilize it. The main problem is that a jacketed smaller bullet can come apart from over spinning because it is moving faster down the tube than the heavy bullet. For pratical purposes, you can't "over stabilize" a bullet. However, there is a place for a slower twist. The slower the twist rate, the faster you can send the bullet toward target. Pressures will be lower in slower twist so you can speed up the bullet with more powder. I can gain 300 to 400 fps more speed from my 75 grain .243 bullets from my custom made 1:12 twist barrell than from the standard 1:9.25 twist.

By running a faster twist than what’s needed chances are your groups will open up some and the bullet will not shoot to it’s potential!!!
Simply slowing them down does not fix the problem because its not a stability factor.

As far as speeding them up for the stability factor.....yes it can be done but you must be working close the edge of stability to begin with.
In most situations you will not be able to add enough speed to create stability.
A while back I found a article written on the subject that had some math associated with it. Damned if I can find it now !!! (I thought I bookmarked it)
Should I find it I'll post it as a reference.