Beartrack posted

The point is that HV can equal the heavies in energy, but not in SD nor MOMENTUM. These alone provide deep penetration from any angle, through heavy bone or muscle

This statement may have some truth if the basic copper jacketed lead core bullets are used.It however is totally incorrect where the new bullet constructions are used.Which do you think would provide better penetration if both were .308" bullets-a 165gr failsafe or a 220gr hornady?The simple truth is that the newer bullet designs such as the failsafe,barnes x,groove,partition,accubond,a-frame,j-36 etc penetrate better than heavier bullets of conventional design.You can now have high velocity without sacrificing penetration by selecting lighter bullets of proper construction.

All the replies are good. In my experience the benefit of heavy bullets is all about the animals being hunted. The High Velocity crowd is right about the effectiveness of HV IF you are hunting light game (deer size) or you have PRECISE bullet placement.

In this manner Roy Weatheryby killed all manner of game w/ the .257 Wby. w/ deadly results. Yet, I ran into a couple of guys in Prince George BC, who planned to use 120 gr. Balistic Tips on Moose in 7 STW with the same idea in mind. I pointed out to them that if a bullet at 3700 FPS hits a rib inside a 100 yds (especially the BT), that's where it will stop! I was told, "You not supposed to hit the ribs." I can only conclude that these guys were either the finest shots I have ever heard of (able to shoot between the ribs of a moose at any range) or they had done WAY TOO MANY DRUGS.

The point is that HV can equal the heavies in energy, but not in SD nor MOMENTUM. These alone provide deep penetration from any angle, through heavy bone or muscle. This is why some praise the .270 as an elk rifle & others curse it. It isn't the caliber, but the bullets and the shot placement.

By the same token, the 6.5x55 kills thousands of moose every year in Sweeden, w/ no complaints. Why? They shoot 140 to 160 grn bullets (providing deep penetration) and often from stands (providing excellent placement).

All of this is they the X bullets are second to none on big tough game. It is often possible to go a little lighter in bullet and still have the penetration.

I know this sounds stupid but please explain it to me.

If we have a common bore size, 30 cal for instance. And use the same materials for both bullets, then the heavier bullet will be longer. And longer, will have increased sectional density. And increased sectional density will mean less deformation and therefore better penetration.

But is that it? Is that the only reason to use a heavier bullet (higher sectional density?). Why not use a lighter material, which would allow you to have the same sectional density, same diameter bullet, and yet have a lighter projectile? Or is that the theory behind monometal bullets like the Barnes X?

Does the weight really effect the killing potential, or does it just serve to increase penetration, thereby increasing the deadliness.

Kinetic Energy = Mass x Velocity (squared) so if you increase mass the energy level goes up. Lighter bullets can be driven faster so the muzzle energy is higher but heavier bullets retain their velocity longer so they have higher energy levels at longer ranges.

The easiest way to think about this, I think, is simply to compare bullet weights AFTER IMPACT. If a bullet weighs 130 gr. after impact, and the next one weighs 110, the 130 grainer will penetrate deeper, if impact energy levels are the same. It takes energy to make a hole and penetrate, and for that the projectile needs to retain mass.

So, yes, monolithic bullets like Barnes X, do penetrate like, say, the next size or two up Nosler Partition, and usually have a better B.C. in flight. And have a little less recoil. What's not to like? JMO, Dutch.

Does bullet weight really matter?

Well what are you doing with it? If you want a high BC, then yes it matters. If you want pure energy for say grizzlies, yes it matters. Do you want to shoot deer with a 308 and use 125's up to 200 yards? Well then it becomes less of an issue in that case. Weighty object generally penetrate deeper and hit harder. So depending on what youre doing, it can matter.

SD is weight divided by square of it's dia., so length doesn't really have anything to do with it. Check SD, a 180ge/.308 from Barnes, Nosler, Hornady all have the same SD. Where the monometal bullets step up is they hold their length longer, thus a light 165gr 'X' can have the same terminal length as a 180gr partition. If your high SD bullet blows up on impact, it's length & mass are reduced & penetration suffers. Kind of what Dutch said.

The year before Finn Aagaard, the famous Kenyian PH who retired to Texas, died he did extensive tests with 220grn.NoslerPartition in a 30.06. His conclusion was that this was the best combination for any game in NorthAmerica. At first everyone was worried about meat damage on smaller thin skin animals like whitetails or mulies but in actuality it did less damage than any other bullet. Pushed along at 2600-2700fps it had more penetration with less bullet deformation than any other combination. The ultimate 30cal hunting bullet combination.

either have X-ray vision, something I've in favor of but have never managed, or have very little real hunting experience. I remain horrified by the number of folks who are hunting whitetail deer around here with a .223. The least gun I've ever used for the purpose was a model 7 in .243 Win. shooting 100 gr. Nitrex factory load. That was in a very steep wooded place where I didn't want to carry a heavy gun and never expected to shoot more than 75 yards. I took a one at about 10 yards. He ran by me at full speed. My shot hit the ball and socket of his right front knee, passed through ribs on both sides of his rib cage but did not pierce the skin on the far side. The bullet expanded evenly and stayed together. I don't believe a 62-75 gr. .223 bullet of any configuration would have give me a clean kill. Didn't someone one say "Use enough gun."

I'm not an expert, but I found the .30 cal. 220 g. RN bullets more effective on game than 180 g. spitzer (just my opinion). Shooting them at 2500 fps, game usually fall like stones, and meat damage is lesser. - Lorenzo

A bullet test conducted in the june 1998 handloader magazine demonstrated just how much effect bullet construction has on penetration.A 180gr partition managed to penetrate from 17"to 19.7" at impact velocities from 2500fps to 3100fps.The 180gr failsafe penetrated from 20.5" to 25.3" at the same velocities.Yet when grand slams were tested in 165gr to 200gr weights there was no significant difference in penetration at all with penetration averaging between 16" and 18" for all weights.

Are we overlooking expansion? The reason the lighter premium bullets are penetrating further than the heavy cup and core are because they can be driven at higher velocity without over expansion or coming apart, hence, not loosing most of there weight.

I DESIRE complete penetration but would like a bullet (338 and under) to expand to at least twice there diameter. That's why I feel that in some cases, especialy in chamberings that pushes bullets under 2,800 fps the ol' heavy for caliber cup and core can be more reliable than a premium.

Stubblejumper

This is interesting coming from you.

I know that you have used BT's with great sucess quite a bit, but now you are talkking about tough bullets?

I also know that alot of your shots are long, so a BT is quite appropriate. Just curious about your take on bullets these days..

Some of the posts here have been very interesting reguarding SD, BC, and momentum. For those of you that are still a little confused I suggest reading Jim Carmichels book The Rifle. It explains just about everything you need to know on the subject. JMO

Gatehouse-My choice of bullets depends on the game that I am hunting.For non dangerous game I am still using the ballistic tip but I am going to try the 180gr accubond in my 300ultramags when it is available in canada.I pick my shots carefully so the ballistic tips haven't been a problem but I do like the idea of a bullet with the accuracy and ballistic co-efficient of the ballistic tip and the penetration of the partition.For dangerous game I would probably use the failsafe or barnes xlc for maximum penetration and the ability to break large bone.I will change bullet construction rather than bullet weight to gain more penetration on larger game when I may not have the opportunity to pick my shots and my life may be on the line.

High sectional density has many virtues that most hunters are not aware of. It is the prime determinant of the BC, which is important for down range energy retention and flat trajectories. However, it is also the prime determinant of terminal bullet performance. As the bullet expands and grows in diameter, its ability to penetrate is reduced, and is a function of the SD for the EXPANDED diameter bullet. A low SD bullet quickly runs out of material and velocity and stops. A high SD bullet will continue to penetrate and move forward with a larger diameter than the lower SD bullet.

If both bullets have equal kenetic energy (FPE), the high SD bullet will create a larger wound channel. This is true even if penetration distance is the same, due to differences in bullet construction. In order to penetrate as far as the high SD bullet, the low SD bullet must expand LESS.

A very good measure of this effect is to multiply SD times velocity to get SDV. A 220 gr 308 bullet at 2600 fps has SDV = 861. To match this, a 180 grain bullet of similar construction needs a velocity of 3176 fps. A 150 grainer needs 3808 fps. Obviously, these velocities place additional challenges on bullet integrity and construction.

With regard to penetration, I have two words for all of you:

MOMENTUM DENSITY

Scott

When traditional bullet designs and velocities are employed the old school train of thought still applies, but today there are other options.

Some folks multiply the KE times SD to make it more reflective of wound channel potential. The SDV measure is indicative of penetration potential.

The practical limit for SDV in sporting arms is a value of 1000. Over that, barrel life and powder charge weight goes off the chart. The 50 BMG can get to 1250 or so. The 120MM main tank gun uses sabots to get to nearly 8000, which of course will go through 8 inches of steel, no problem.

Bullet design has nothing to do with.

Sabot,

SD * V = MOMENTUM DENSITY

SD * KE = ENERGY DENSITY

Momentum density = penetration potential


Both densities are EFFECTED by expanding bullets. Since the frontal area increases as the bullet expands!

Simple stuff gentlemen, let us not make things too difficult.

A real (read accurate) mathematical solution for expanding bullets and penetration gets very complex, but the concept is simple and straight-forward.

Scott