December 1, 2019, 03:56 PM | #1 |
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Bullet choice
I started to review an old copy of the 5th Edition of “The ABC’s of Reloading “, to refresh what I may have forgotten, and I zeroed in on an area I had never read- a mathematics section.
I got interested in the discussion about “momentum” vs kinetic energy since I don’t recall ever hearing the latter term used with respect to bullet selection. “Momentum” is basically described as having a linear direction whereas kinetic energy is multi-directional. I compared two bullets comparing both physical properties: I calculated the momentum of a 150gr spire .308 bullet traveling 3000 fps, then figured out what velocity would be needed to produce the same momentum in a 180gr spire. Since all data will change as velocity changes over a 300 yard distance, two things stood out: 1) The 150gr bullet had a “flatter” trajectory and more kinetic energy 2) The 180gr bullet had a greater momentum after it left the muzzle I understood that kinetic energy, being multi-directional, imparted its energy in the animal target in a dispersed manner, creating the “shock” wave which damages vital organs in addition to the bleeding that occurs with that wave and fragments from the bullet. Momentum, on the other hand, speaks to depth of penetration. But I’ve only ever heard of bullet construction as a factor in the depth of penetration, and nothing about momentum, which is the tendency of a mass continuing to move once accelerated. It would seem to me that two bullets of equal weight and velocity would have the same momentum, and thus penetration potential. Solid lead and copper of the same weight and velocity should not able to have penetration improved by the construction of a jacket or tip that initiates expansion of the projectile. From the table I developed these two bullets of equal construction but different weight reveals although the lighter bullet retains more energy and has a flatter trajectory, the heavier bullet retains more momentum across the range ending at 300 yards. Would that bullet be a better choice where a 300 yard shot is more likely anticipated? Is there any hunt where more attention should be given to momentum? Bullets: Hornady .308 Interlock, 150gr Spire and 180gr spire, 200 Yd zero. 150gr BC .388 Muzzle 100Yd 200Yd 300Yd FPS 3000 2721 2459 2212 KE, ft-lb 2997 2466 2014 1630 Momentum 1.998 1.812 1.638 1.473 Trajectory -1.5 1.6 0 -7.4 180gr BC .425 FPS 2500 2300 2110 1929 KE-Ft-lb 2498 2115 1179 1488 Momentum 1.998 1.838 1.686 1.542 Trajectory -1.5 2.5 0 -10.4 Sorry, it seems no matter what I do, I can't get the table to appear as a table. |
December 1, 2019, 04:23 PM | #2 | |
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December 1, 2019, 05:25 PM | #3 |
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Momentum matters more in archery than firearms in North America.
Not like your trying to stop an angry elephant or water buffalo.
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December 1, 2019, 07:26 PM | #4 |
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Bullets don't kill. Bullet holes kill. There are 2 factors in the hole itself and one other, that being the trauma done in making the hole. The 2 factors that can be "adjusted' in the hole are depth and diameter. That's it! That's all there is.
The 3rd factor is the shock effect you can get from certain bullets at a given impact velocity can achieve. The "3rd factor" is quite variable depending on the angle it strikes and what it strikes. This is the part of ballistic studies that has all the "weird stuff" that drives ballisticians crazy. In my many years of hunting I can tell you more energy may or may not kill a game animal quicker. Energy, as long as there is "enough" to give full penetration and also expand the bullet will not produce a quicker kill if you increase it alone. How that energy is transferred (or failed to transfer) is a field of study that is nearly bottomless. There are also more variables than can easily be counted. I have personally killed a few smallish deer with a 458 Winchester that seemed "lightly hit" for a few seconds after the shot because for all the power it has, very little of that power was used on the body of the deer, Probably 95% was used to dig a large pock in the hill behind. The entrance and the exit were almost exactly the same size on those deer. A 270 with a good 130 grain bullet on the other hand has WAY LESS energy then a 458, but the deer fell as if hit by lightning. The 270s, with far less power, dump about 80% of the power they have inside the deer. So when you speak of the difference in the effect of a 180 grain or a 150 grain load, unless you are shooting game large enough to stop the bullets I doubt you can see any difference in the effectiveness of either weight as long as we compare apples to apples. As an example, a 150 grain Nosler Partition and a 180 grain Nosler Partition are both going to exit a deer and both leave about the same diameter hole behind. So both are going to work about the same. Go up to bull elk or moose and the 150 grain probably will not exit, where the 180 may. So on a larger animal the effect of the heavier bullet may be more noticeable. The hole can only be 100% deep, but 100% in a 850 pound elk is a LOT more then 100% in a 150 pound deer. Bullets that fragment make the largest diameter holes but also the shallowest as compared to the other design of bullet which holds it's weight, makes a deeper hole (remember, 100% is the deepest you can get) and are usually more reliable killers even if those kills are not quite as dramatic. Fragmenting bullets can and probably about 5% of time DO make woulds in shapes and at angels you DO NOT want. It often takes scores of kills over dozens of years to see the pattern, but the pattern is indeed there. I have killed more big game then I can count in many states and in a handful of other countries, and I have been doing it for over 1/2 century. So I have seen the patterns, and I speak from experience here. But to wrap up, if you use a good bullet that will give you an exit on what ever game you are hunting it matters little what it weighs in the barrel. As long as it weighs enough to exit the game it's (A) heavy enough and (B) well made enough. If the 150 and the 180 both double in diameter in their expansion the holes they make in the game are going to be very similar in diameter. If the game is large and you are in doubt, it's often best to err to the heavier size. Get the bullets to exit after full penetration in a pretty straight line and you have done all that caliber really can do. Last edited by Wyosmith; December 1, 2019 at 07:38 PM. |
December 1, 2019, 07:36 PM | #5 |
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Both momentum and energy are irrelevant and no one has paid any attention to either in years.
Momentum is a good way to predict how well a bullet will knock over a steel plate, but does nothing to predict how well bullets perform inside living creatures when the bullet hits. Energy numbers alone are useless. They CAN be used to predict how well a bullet will expand if all other variables are removed from the equation, but that isn't possible. If you're comparing very similar bullets then energy numbers might be somewhat useful. If not you can easily get very misleading information. This is especially true when comparing different calibers. Here is what you need ask when choosing bullets. Does the bullet give adequate penetration to reach the vital organs of the game being shot? That is based on the bullets sectional density and construction. The Interlock bullets you used are sorta middle of the road as to construction. Others are tougher and will penetrate deeper, others are softer, will expand rapidly and may not penetrate enough to reach vital organs. What is the bullets sectional density (SD)? That is a ratio of the bullets weight and diameter. Within the same diameter a heavier bullet has a higher sectional density and assuming equal construction will penetrate deeper. The 180 interlock will out penetrate the 150 interlock by a good bit. But if you were shooting a soft 180 gr bullet and a tougher 150 the tougher 150 will penetrate deeper. On deer size game any of them will give more than enough but on bigger game the deeper penetrating bullet might be needed. But when you change calibers it gets interesting. A 30 caliber/180 gr bullet has about the same SD as a 26 caliber/140 gr, a 27 caliber/150 gr a 28 caliber/160 gr and a 33 caliber/225 gr. If we are shooting the same type bullet in all of those calibers penetration in game will be virtually the same. Will the bullet impact at the speeds it was designed to work? The interlocks you chose are typical of most bullets and work well if they impact between about 1800 up to about 2800 fps. If they impact below about 1800 fps they don't expand and act like FMJ. Above 2800 fps and they may over expand and not penetrate. But not all bullets are the same. Some will stay together well over 3000 fps, but those are also the bullets that need more than 1800 fps or they don't expand at all. Some need to impact at 2000-2200 fps to work. You don't choose the same bullet for a 308 and 300WM. The 150 leaving the muzzle at 3000 fps are very likely to fail at close range. Once they slow down at 100-150 yards would work better. Or just use them in a 308 where they are starting at about 2800 fps. If you're going to shoot 150's at 3000 fps you need to choose a tougher bullet designed to work at that speed. It's just too complicated to try to use simple energy or momentum numbers to predict which bullets will be more effective with modern bullets. Back in the 1700's with smokeless powder and round balls those numbers were relevant. Not anymore.
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December 2, 2019, 12:05 AM | #6 |
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".....bullet holes kill....."
I gotta remember that one!
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December 2, 2019, 10:41 AM | #7 |
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Great responses and explanations! Education for everyone!
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December 2, 2019, 11:10 AM | #8 |
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"...Momentum matters more in archery than firearms..." Momentum doesn't matter at all for hunting.
"...a mathematics section..." The reference chapters in most reloading manuals are an interesting read, but they can make your head explode. The formula for figuring the BC of a bullet, for example. Ballistics Coefficient being how a bullet overcomes air resistance and nothing more. "...Back in the 1700's with smokeless powder and..." No smokeless powders then. No smokeless until very late in the 19th Century.
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December 2, 2019, 12:34 PM | #9 |
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Imagine sitting there getting ready to take a shot and suddenly overcome with this problem!
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December 2, 2019, 01:14 PM | #10 |
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I love these threads, I really do!
Especially content like Wyosmith and JMR40 put up. It keeps me thinking, it keeps me interested in learning more. It also challenges me to pay attention to everything I can observe in the field, even at the meat processing table. I also like it when it stays at the level of thoughtful conversation, rather than heated debates. But I also think it's important to note that these more subtle differences and distinctions aren't the primary factors in the results of actual shooting. They're the 10% (give or take) of what's left when all the hardware, technique, practice, and situational factors have had their say. Whether target shooting or hunting, these fine-tuning, academic factors will only determine success vs failure 1 or 2 times out of 100. I guess my point is that none of this stuff will make up for poor shot placement and/or decision making. But it is, of course, still most enjoyable to discuss/learn.
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December 3, 2019, 01:04 AM | #11 |
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Right on target, Tallest. What makes this forum better than any other (of all topics) is the continued interest in sharing knowledge and experience rather than arguing about opinion.
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December 4, 2019, 02:53 PM | #12 | |
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December 4, 2019, 03:11 PM | #13 | |
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December 4, 2019, 05:26 PM | #14 | |
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Same shot with my 7 Rum is ALWAYS a boom flop. I personally double lunged a deer with 7- 08 that went 300 yards. Now I hunt with 257 Roy, 7 Rum, and 6.5x300 Wby almost exclusively. For the record, none of the 3 cause any real meat loss when double lunged. Now you put a 150 from the rum in a shoulder blade, you lost 25 pounds of meat, but I dont shoot them there. Last edited by reynolds357; December 4, 2019 at 05:32 PM. |
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December 4, 2019, 10:00 PM | #15 | |
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December 4, 2019, 10:01 PM | #16 | |
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December 5, 2019, 12:43 AM | #17 |
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December 5, 2019, 09:27 AM | #18 | ||
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I hunt almost exclusively with a 7-08. And I have to track deer maybe 10% of the time. This year, for example, I tagged out with 5 white tail. The farthest any went was about 8 steps. My sister in Montana hunts mule deer with a .308, and while a 150 grain .308 bullet is heavier than a 140 grain .284, it's by no means at magnum speed. Generally, in what you're describing, I'd wonder more about bullet choice than velocity. To me, escalating to a magnum round seems, for lack of a better word, a lazy way to make it the animal more dead. Especially since the increased potential damage can be wasteful. Not going for a personal attack here, really. It just doesn't seem that any north american deer species would require the difference from a 7-08 to 7Rum to go down quickly, unless you're regularly shooting >300 yds. And again, just my 2 cents. I really don't get too worked up unless someone is knowingly allowing an animal to suffer.
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December 5, 2019, 11:24 AM | #19 | |
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December 5, 2019, 03:32 PM | #20 |
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I shoot em in the lungs, using (these days) 120 gr Ballistic Tips in my 260. They don’t run 300 yards. If they did I would rethink the bullet I was using, or guess that I just nicked the lungs rather than destroyed them. Destroy them and they go maybe 40 yards, if that far. Nick the lungs, and they can still breathe, and a long run is certainly possible.
This is data personally gathered over 50+ years of hunting and a couple hundred lung shot deer. |
December 5, 2019, 04:00 PM | #21 | |
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December 5, 2019, 04:33 PM | #22 |
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Well, in my long and happy relationship with Nosler Ballistic Tip bullets, I really do have a hard time imagining that a center of the lungs shot with that bullet didn’t totally destroy the lungs. Not saying you didn’t see what you saw, but if anything, the bullet trends toward too much destruction rather than too little.
As for the ttsx, I have no experience with that bullet. |
December 5, 2019, 06:08 PM | #23 | |
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December 5, 2019, 07:04 PM | #24 |
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Dang. This is really an elightening post. I had no idea all of the folks who hunt with rifles that shoot slower than 3200 fps have to track and follow up their game animals for several hundred yards.I wonder how many lose the ones "only" shot with a 7x57 ,or (gasp) a 257 Roberts or 250 Savage.
Funny,I started out hunting as a teen with a 7mm Rem Mag,and at that time with surplus H-4831 I was loading 70 gr behind a 160 gr Sierra boat tail. DO NOT TRY TO USE THAT LOAD!!! It was hot with surplus H4831,and would be DANGEROUS with newly manufactured H 4831. I got tired of wrecking too much meat. The 1970 is version of a 160 gr Sierra Boat tail was a bomb. I quit hunting with that cartridge. I buily a 257 AI. I use a 115 gr Ballistic tip. I never used it on elk,but it kills quickly and dependably on deer and antelope. The "Hole" Wyosmith mentioned is typically the size of a football. In my experience,a "double lunger" results in pouring a soup of blood and heart and lung chunks from the body cavity. A "double lunger" with a 165 gr Ballistic Tip from a 308 ,just barely flying at only 2750 fps or so seems to kill elk quicky, with a similar chest cavity full of borscht and sponge bits. I must be doing something wrong. I'm not hunting much these days. Body is tired. BUT IMO,a little CZ or Howa bolt action could be made into a 6mm,6.5,or 7mm Rem Benchrest or a 6.5 Grendel to be a fine 250 to 300 yd deer and antelope rifle. I would not be scared they'd run away with a "double lunger". And I don't think a young or slight new hunter would be handicapped at all by a mild cartridge. Folks tend to shoot better with mild cartridges. I've noticed a lot of the fun and excitement happens when you are getting 100 yds closer. |
December 5, 2019, 08:28 PM | #25 | |
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