300 or 7mm mag?

[sheephunter]

Bullet inflicted damage to game is a function of construction, impact velocity, and bullet placement. If the bullet expands to .60" the shank diameter has little to do with the wound volume. GS Custom in RSA is a maker of mono-metal bullets similar to the Barnes TSX, and they have pics of game shot with a 45 gr .224 bullet from a cartridge that is essentially a .22/06 with a MV of nearly 5000 fps. They claim the game drops as if hit by lightning with less meat damage than the same game shot with 100 gr .243's. Me being a fancier of heavy for caliber bullets at moderate velocity, sees that a brave new world in bullet performance could be emerging.

I think the one factor that needs to be stressed, however, is how much metal the bullet sheds as it travels through the animal. Bullets with low weight retention cause extensive damage to meat with fragments traveling up to 18" from the wound channel.

There are basically two types of meat damage......one from that actual shock of impact and the other from foreign particles traveling through the meat, so a rapid expansion bullet or even an old favourite like the Core Lokt can do far more meat damage traveling at a realatively low speed when compared to a bullet like the TSX going at high speed.

 

[Boomer]

You'll see that I did say there is a usefulness of comparing identical bullets of different weights but even with similar bullets, there are still too many variables in expansion for SD to be an accurate formula. Once we put a jacket on bullets, SD became basically obsolete.

As a means of comparison of the relationship between bullets of various calibers, SD continues to be relevant. We know for example that it takes more pressure to drive a 150 gr .270 bullet to 3000 fps than it does to drive a 150 gr .30 caliber bullet of similar design and construction to the same velocity. Thus the .270's SD of approximately .279 compared to the .308's SD of approximately .226 provides a numerical basis for comparison so that the difference between them can be understood.

With respect to SD in the context of expanding modern big game bullets, if we consider the limitations of bullet expansion, we see that expansion seldom exceeds these limitations, and that a loss of performance occurs when these limitations are exceeded. The expansion must leave the bullet with a linear axis to rotate around. The expansion should not exceed 2.5X the shank diameter or instability can result if the expanded frontal area is not exactly symmetrical. The thickness of jacket, depth of hollow point, and hardness of core all effect the rate at which expansion can occur, but the actual expansion is controlled within very tight parameters considering the forces at work. Thus when we want to decide on a moose bullet for our new rifle, and we have experience with a bullet with a SD of .279 we have a basis for comparison, regardless of caliber or weight. Thus if we have had good results with our .30 caliber 180 gr bullet we would expect similar results with a 140 gr 6.5 bullet or a 225 gr .338. This is not to say a bullet with a SD of 225 would not perform admirably, but is provides us with a basis of comparison when bullets of similar construction are chosen.

 

[sheephunter]

As a means of comparison of the relationship between bullets of various calibers, SD continues to be relevant.

Only if those bullets are identical in construction.....ie all the same brand/model and then it still means very little because there is no benchmark SD number in regards to penetration or effectiveness. What is a required SD these days? There is no way to say as each bullet performs so differently. It might be fun to compare SDs on paper but sadly, the number means absolutely nothing in the real world unless you are still chucking lead conicals.

With respect to SD in the context of expanding modern big game bullets, if we consider the limitations of bullet expansion, we see that expansion seldom exceeds these limitations, and that a loss of performance occurs when these limitations are exceeded. The expansion must leave the bullet with a linear axis to rotate around. The expansion should not exceed 2.5X the shank diameter or instability can result if the expanded frontal area is not exactly symmetrical. The thickness of jacket, depth of hollow point, and hardness of core all effect the rate at which expansion can occur, but the actual expansion is controlled within very tight parameters considering the forces at work. Thus when we want to decide on a moose bullet for our new rifle, and we have experience with a bullet with a SD of .279 we have a basis for comparison, regardless of caliber or weight. Thus if we have had good results with our .30 caliber 180 gr bullet we would expect similar results with a 140 gr 6.5 bullet or a 225 gr .338. This is not to say a bullet with a SD of 225 would not perform admirably, but is provides us with a basis of comparison when bullets of similar construction are chosen.

As I said, it may be fun on paper but it means nothing when you start shooting bullets like the CPX3 or TSX or even bonded bullets for that matter. At one time SD was an important calculation because it gave a good idea of what calibre/weight bullet you needed to achieve desired penetration. Today it doesn't and other than serving as fodder for internet discussion, its usefulness is gone.

 

[Gatehouse]

I'm not sure if you guys are aware of this...But I'll say it...


If you use a good bullet and put it in the right place, the animal won't care about SD, BC, metal shedding, or any of the rest of the numbers...

 

[sheephunter]

I'm not sure if you guys are aware of this...But I'll say it...


If you use a good bullet and put it in the right place, the animal won't care about SD, BC, metal shedding, or any of the rest of the numbers...

You do have a way with words but you sure take the fun out of the interweb.....

 

[Boomer]

I'm not sure if you guys are aware of this...But I'll say it...


If you use a good bullet and put it in the right place, the animal won't care about SD, BC, metal shedding, or any of the rest of the numbers...

This is very true, but how does one define what a good or even what a suitable bullet is for any given job? Our choices are based on advertising, heresay, or experience, ranked in importance from the least to most reliable.

Once we have experience with one bullet in one application, how can we be sure that another bullet might produce similar results? Because a good bullet's expansion does exceed 2.5X its shank diameter, and because it must be long enough to rotate around a linear axis once fully expanded, it will have enough weight to penetrate deeply enough to do the job. The shorter bullet will be faster, the longer bullet will be heavier, so penetration evens out.

A broad range of bullets weights is suitable for taking game of a certain weight, if we observe the precept of a reasonable expectation to kill the game animal with a single shot from any angle within the range limitations of the cartridge. SD is therefore a useful basis of comparison to help us choose a bullet within the range of bullet weights available for a particular job. Bullet construction effects the rapidity of expansion but not the extent of expansion, if it was a good bullet to start with.

 

[shortaction]

Only if those bullets are identical in construction.....ie all the same brand/model and then it still means very little because there is no benchmark SD number in regards to penetration or effectiveness. What is a required SD these days? There is no way to say as each bullet performs so differently. It might be fun to compare SDs on paper but sadly, the number means absolutely nothing in the real world unless you are still chucking lead conicals.


As I said, it may be fun on paper but it means nothing when you start shooting bullets like the CPX3 or TSX or even bonded bullets for that matter. At one time SD was an important calculation because it gave a good idea of what calibre/weight bullet you needed to achieve desired penetration. Today it doesn't and other than serving as fodder for internet discussion, its usefulness is gone.

So you believe that 2 TSX bullets of same caliber but different SD fired at the same velocity into the same medium would penetrate equally?

 

[sheephunter]

So you believe that 2 TSX bullets of same caliber but different SD fired at the same velocity into the same medium would penetrate equally?

No! That would be stupid to believe that.

 

[Algonquin]

Which?

I use a .338wm for moose with a .300wm as back-up. Also have a 7mmrm and like all three as standard magnum calibers. I have confidence in the way the .300wm shoots, not sure why but it just works so well.



All are great choices.

FM

 

[lucky72]

i think that they all good caliber.just need to practice more to get use to the recoil.

 

[shortaction]

So you believe that 2 TSX bullets of same caliber but different SD fired at the same velocity into the same medium would penetrate equally?

No! That would be stupid to believe that.

So do you believe that 2 TSX bullets of same SD but different caliber fired at the same velocity into the same medium would penetrate equally?

 

[sheephunter]

So you believe that 2 TSX bullets of same caliber but different SD fired at the same velocity into the same medium would penetrate equally?



So do you believe that 2 TSX bullets of same SD but different caliber fired at the same velocity into the same medium would penetrate equally?

They would be close for sure.....in would depend on the medium a bit but for arguement sake, yup, they'd penetrate the same distance.

If you think I don't understand SD, you are wrong and if you think that I'm trying to disprove SD, again, you are wrong and I think I've stated a couple times on here that the formula works with identical bullets so I'm not sure of the point of your little questions. What I'm saying is that the formula has no practical purpose with modern hunting bullets other than for guys to argue on a messageboard or for manufacturers to convince you that their new cartridge is the best because of its high SD.

The SD formula works so let's get past that....it just has no real world application with jacketed bullets.

 

[srt4u2nv]

Going to be loading some 150gr TSX's for my .300wm in a week or so should be a great load for what ever I may incounter.