Can someone explain this?


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gamestalker
September 16, 2011, 06:46 PM
I think one of the most debated topics of hunting weapons and bullets is based on velocity, bullet weight, and construction properties of the projectile it's self. My thoughts, and to some degree testing results, have been with the 7 mag. and .270 win. with the 7mm RM the center of my most recent pet cartridges. I was sitting here thinking of which bullet to try out this huntng season for mule deer using my 7mm RM with a lot emphasis on penetration and down range velocity, obviously.
I started with a 120 gr. standard Hornady PSP bullet @ 150 yds. down range @ a chronographed M.V. velocity of just under 3300 fps, it consistently and completely blows through a 1/2" piece of average grade plate steel. However, a bullet only 20 grains lighter at a velocity of nearly 3600 fps doesn't get through and barely fractured the opposit side. Both bullets are nearly identical in structure, I have sliced them in half from heel to tip and everything looks to be equal in jacket thickness less the 20 grains of weight in the 100 grain projectile. Considering that the 100 grainer is moving at least 300 fps faster, I would have thought the small difference in weight would have been compensated for in energy with the 300 fps advantage. Not so as it appears?
Well I continued with my research by loading up a 120 gr. solid copper projectile and a 100 grain solid as well. The 100 grainer @ 3623 fps fractured the opposit side and looked promising to me as a long distance deer hunting load. So I loaded up the 120 gr. solid @ almost 3300 fps and expected a simular performance as the 120 gr. jacketed Hornady round, but I was astonished to discover that it will not go through. It did produce a very visable fracture on the opposit side, but several trys didn't improve nor change it's effect on the steel.
So after these rather poorly controlled testing senario's, I decided to put a thin skinned 5 gal. plastic container filled with water behind it to catch what ever comes through, thinking this mght help answer some questions. But it actually presented me with more questions than answer's. I put the 120 gr. jacketed bullet through, and when the round punched through the water container it nearly exited as well, leaving a split on the opposite side. When I looked to see what was left of my bullet, I discovered what was laying on the bottom of the water container appeared to be a steel half moon .510" diameter plug that weighted in at 28 grains more than the projectile, 148 grains. When I got home I heated the plug with a propane tourch so I could melt away any lead. To my surprise the plug had no lead to be found. So now I'm thinking that it is shear energy that punched the hole. It looks like it was perfectly cut with a plasma cutter, and not even a small frag of lead or copper could be found in the water jug.
In future steel plate testing I tried some heavier bullets, 130 gr. jacketed PSP, 139 gr. PSP, and a 168 gr. PSP. all but the 168 grainer went through, but the 168 did leave a nasty crater and was very close to breaching the opposite side. So now I'm kind of thinking I can use this information to at least some degree regarding penetration. In this repsect, I'm kind of thinking that a 130 gr. to 140 gr. is going to produce the best penetration on dense tissue game, bear elk and such. It seems at some point a heavier projectile looses it's ability to penetrate because it's velocity drops below an effective range, much in the same respect as to the lighter faster bullet looses it's effective mass, to utilize it's extreme velocity, but in a reverse manner. In other words, it appears the heavier mass at a lower velocity of 3050 fps average, isn't enough to maintain enough energy to breach the steel. But on the other side of this is the lighter bullet, which I pushed at up to nearly 3700 fps in my final attempt, still doesn't have enough mass to breach the plate. I also tried the HP 100 gr. and 110 grain bullets with nearly identical results as the PSP 100 gr. projectile, theydon't get through.
So now I think I've found that the optimum penetrating projectile seems to be between 130 gains and 145 grains. For mule deer, I think either of those are going to produce a good clean entry and exit hole. But if I were hunting something a little bit more dense such as elk or bear, I would probably not go any lighter than a 145 grain projectile, but probably not any heavier either.
I'm now thinking the "bigger is better" mentallity may not be the optimum choice, especially at distances out to 300 yds.. So I'm still not sure about extreme distances of over 500 yds. and up to 800 yds, which weight .284 projectile is going to provide a good clean kill on mule deer sized game. I once thought the solid copper projectile was a magical pill in this respect, but even that is starting to look bleak in relation to the steel penetration experiements, with lead clearly out performing them.
I've sucessfully hunted everything from antelope to elk and bear with both the .270 win, and the 7mm RM over the last several decades. Many of my kills have been at distances out to and beyond 500 yds. with all kills acomplsihed with the mid weight projectile. I have always hand loaded bullets that have never exceeded 145 grains for the 7 mag., and 130 grains being the heaviest for the .270 Win. for these animals of the southwest. But recent events have forced me to question my choices, primarily speaking I'm trying to rule out pure luck, as the common denominator here.
Has anyone else possibly done more extensive testing or can contribute their perspective based on an event or possibly an extensive study, and even some relative results from a hunting experience that may shead some more light on the optimum long range pill, primarily the 7mm RM or potentially simular velocity .284" projectile. Your thoughts and perspectives are open mindly welcomed on this topic. I've long enjoyed proving or eliminating various therory's and opinions, almost as much as the sport of big game hunting it's self. But like most who enjoy reloading, I'm always searcing for the magical pill that will do it all at just about any distance, and I think I might have discovered some specifics that help explain my findings enough for my specific application. Though the steel plate has provided some standard of performance, the ability to dispatch big game at long range is the motive behind wasting all those bullets.

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scythefwd
September 16, 2011, 06:52 PM
format that please... I re-read the same sentence three times due to getting lost in the sea of text.

TL : DR

T Bran
September 16, 2011, 07:16 PM
GAMESTALKER
Great post and quite puzzling that a mere 20 grains in bullet weight appears to be more of a factor than the additional velocity. I read once that above a certain velocity both the bullet and the medium it strikes behave more like a liquid than a solid. However your testing seems to contradict what I thought I knew. The metal slug that was left in your test seems to indicate that the bullet acted more like a punch press while the slug must have either vaporized or formed a new alloy with the steel ( haha). Very interesting ill stay tuned in the hope someone far brighter than me can enlighten us further.
T

USSR
September 16, 2011, 09:49 PM
Conclusion: velocity is not a substitute for mass when it comes to penetration. Now you know why the 6.5 Swede kills game all out of proportion to it's caliber and velocity.

Don

gamestalker
September 17, 2011, 03:12 AM
Thanks guys for the input. I would have to agree that mass is one of the most effecting elements. But as I demonstrated with the 168 grain ullet, it seemed to lack the velocity at just barely above 3000 fps to get through. Seemed strange to me considering 3000 + fps isn't a really a low velocity round per say, but it deffinitely appeared to have some bearing in this test?
Sorry about my pargraphing and thanks for the advice. I thought I had it written well enough to project my message, but I guess I still need to work on that some more.

gamestalker
September 17, 2011, 03:14 AM
You know Don I've been wanting to get my hands on one of those 6.5's Swede's for a while now. It just has so much potential in this manner.
What is the typical bullet weight for that cartridge Don?

scythefwd
September 17, 2011, 05:43 AM
Not surprising at all that 20 gr of weight made that much of a distance. Also not too much of a surprise that the coppers had more trouble making it through where the jacketed lead bullets didn't. Copper will peel off and stick to the hole it's punching through. Lead just deforms into itself and keeps pushing through.

There are several things that need to be taken into account for penetration. Kinetic energy, an object at rest tends to stay at rest.. and object in motion tends to stay in montion, is a BIGGIE. You're firing the lighter bullets faster, which gives more energy.. but usually when we talk about muzzle energy we are talking Ft Lbs. That is a measurement of pressure, or how much pressure that bullet is exerting at that time. It doesn't take into account kinetic energy at all (they are not the same). I'll be lambasted for this, but I believe my statement to be true. A 18,000 lb 1/2" diameter spike moving .5 fps will go right through you and probably not even slow down. It may just take you with it instead of going through you. Our little bodies just don't have the mass and cannot provide the friction to stop it. It has a whopping 70 ft lbs of energy according to the ballistic calculator I used online.

My point is that a lighter bullet has a higher energy, but it doesn't really have the penetration. A slower heavy bullet will penetrate better all other variables being equal (which they never are). The higher speed bullet will cause more cavitation in the wound channel, and that will result in very ugly wounds in soft tissue. Steel doesn't cavitate like that and can absorb a lot of energy before deforming...

Either way, that is one hell of a thump you are putting on anything you can hit with those numbers.

GooseGestapo
September 17, 2011, 07:41 AM
Welcome to the world of physics and engineering.

You've got several things going on.
1. Your test media. Metal plates and bullets react differently than living flesh and bullets.. You are seeing the difference. The 120-140gr bullets optimize the velocity/mass trade off in the 7mm bore given case capacity of the 7mmRemMag. Indeed as you discovered, the lead is vaporized and the copper is too, to some extent, and some is deposited on the metal plate. The steel slug you found is the remant of the steel that is converted to plasma and ejected from the plate, whereas the hole in the steel is the vacant space vacated by the remant.
2. The 168gr bullet has more "MOMENTUM", whereas the 139-140gr bullet's have more "KINETIC ENERGY". Now you know where the velocity/kinetic energy kills vs. big bore/momentum kills arguments have been coming from and going ever since fr. Bacon revealed the recipe for black powder.
3. Indeed, bullet constuction and materials characteristics make a difference in the on target performance.

You have reproduced the culmulative testing of small bore weapons for the last 150yrs. Now you know why the .30/06 lives on in the 7.62x51 Nato (aka .308wcf) and still uses a ~150gr bullet at 2,750fps. Ditto the .50BMG is still an anti-material weapon after neary 100yrs and no end in sight. And, bullet construction has change little over that period of time. Also the reasoning behind the 5.56x45 aka .223Rem in the M16. The military is more interested in puching holes in metal (causing casualties) than putting meat on the dinner table. Tungsten makes a better bullet than lead/copper, but, the disadvantage of much greater cost and adaptability to gun bores.

helotaxi
September 17, 2011, 08:06 AM
Bullet penetration is a factor of velocity, sectional density and bullet construction. This isn't a big mystery.

Compare the penetration of the same bullet at two different velocities (within its performance envelope, too fast it will disintegrate regardless of construction type, too slow it will fail to expand and punch right through). The higher velocity bullet will penetrate farther.

Likewise compare the penetration of two bullets of the same weight and construction but different calibers. When impacting at the same velocity, the smaller caliber bullet with its higher sectional density will penetrate more.

Finally, bullets with heavier construction, all else being equal, will penetrate farther.

Penetration is not hardly the only measure of performance. Penetration only needs to be enough to reach the vitals. More important is that the bullet cause as much tissue damage as possible to those vital organs. This pretty much requires a bullet that expands or fragments. Performance on steel is not an accurate representation of performance on game.

ranger335v
September 17, 2011, 08:51 AM
No offense but I don't care what any problem may be enough to work my way through such a mass of writting devoid of punctuation/paragraphs.

USSR
September 17, 2011, 11:00 AM
You know Don I've been wanting to get my hands on one of those 6.5's Swede's for a while now. It just has so much potential in this manner.
What is the typical bullet weight for that cartridge Don?

The Europeans use bullets of about 160gr to kill big game with, whereas on this side of the pond, we tend to use bullets of about 140 grains.

Don

Walkalong
September 17, 2011, 06:06 PM
Now you know why the 6.5 Swede kills game all out of proportion to it's caliber and velocity.Sectional density. :)

USSR
September 17, 2011, 06:59 PM
Sectional density.

Yep. I just got a mould the casts a 235 grain .30 caliber hollowpoint. My intention is to load them at 1600 - 1800fps. Should be quite the Whitetail load at the short distances we shoot them here in upstate NY.:)

Don

Walkalong
September 17, 2011, 07:19 PM
The 7MM Mauser is a good deer gun for the same reason, using the heavier bullets it was originally designed to shoot of course.

ants
September 17, 2011, 07:21 PM
I'll have to go back and read the rest of your original post.
The small print on my computer got my eyes buggy.
Sorry for not reading it all, I'll get back to it. I promise.

Here are my 7mm Rem Mag ideas. Offered in good spirit. YMMV. TIOLI.
(Take It Or Leave It -- I just made that one up.)


Yes, I can get 110 and 120 grain to move really fast, but it doesn't do me much good.
They are not nearly as accurate in my 1/9.5 twist barrels. And the deer certainly don't need that velocity.
140 grain bullets give me the best, best, best accuracy in my Remington.
And at 300 fps slower, they open up better in deer size game (antelope and elk included).
And they shoot plenty flat enough for long shots in the 7mm Mag.
I don't use heavy duty dangerous game bullets with high copper/lead ratio,
nor solids unless I go on a shoot in California's restricted areas.
Nosler makes perfectly good bullets for my deer purposes. So do the others.



On the punching of holes in 1/2" steel:
It has to do with energy transfer.
The ones that didn't fully penetrate transferred 100% of energy to the steel.
The ones that punched through did not, energy goes out the other side.
For hunting medium game, your bullets penetrate and exit much of the time.
On the way through, you wish it to leave as much energy as possible IN the animal.
Personally, I would not be impressed with a deer bullet that passes clean through steel.
That's not exactly what I want it to do.
YMMV and TIOLI.
:)


PS: I don't have any 6.5mm guns. I'm jealous of you guys.

Funshooter45
September 17, 2011, 10:35 PM
Deer aren't made of steel nor do they wear armor plating. That's the reason why you seem to see puzzling penetration figures. For my 7 mm mag, I have found my best accuracy with either 150 gr Nosler ballistic tips or 160 gr Sierra BTSP. The Noslers are slightly more acccurate, although they have a reputation for violent expansion resulting in meat loss. But they seem to knock the elk dead, which is what I want. I did finally get at least decent groups with the 139 gr Hornady SST. But typically, if I pick up the 7 mm that day to go hunting, I'll grab some of the 150 gr Noslers. I just have a lot of confidence in them. They are travelling along pretty fast with a near max charge of RL-22. And I know they'll penetrate and expand well.

Likewise my 270 WSM shoots a 150 gr Sierra the very best of all. The velocity for the 150 gr Sierra in the 270 WSM is basically identical to the velocity of the 150 gr Nosler in the 7 mm mag. Accuracy is likewise extremely good.

For those 2 rifles then, it's pretty much a given that I'll be shooting a 150 gr bullet no matter if it's deer, elk, or moose.

If you're looking for some kind of commonly available test medium, perhaps wooden 2x6 planks at 100 yds is a closer substitute for flesh than steel is. Not exactly the same, but the penetration tests will be more similar than steel plate.

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