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30-11-2017, 18:43 #1
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Lighter and heavy bullets-momentum
I am not too clued up on the scientific aspects of terminal ballistics. I know, if you place a bullet in the vitals, the animal goes down, I recently contacted a hunter, who even wrote a shot placement book, well known in the DG hunting circles. My question was based on monos and lead core in the smaller caliber s, such as the 308s etc. I asked if the 150gr monos have the same potential as the 180g lead cores. Please explain this statement below and if there is truth in it.
Remember – the lighter bullet can be shot faster but despite this it will have less momentum than a heavier 180 going slower – at the shorter hunting distances, a lighter faster bullet will have more kinetic energy but less momentum – this means it will not penetrate as well and by ‘giving up’ its energy more quickly, a lot more ruined, ‘blood-shot’ meat occurs.
For bushveld conditions, big, heavy and slow is the way to go if you want to eat ‘up to the bullet hole’ as we say!
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30-11-2017, 19:23 #2
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Re: Lighter and heavy bullets-momentum
308 win
150gr vs 180gr
150gr at 2800ft/s:
2612 ft.lbf
And
3541 joules
180gr at 2600ft/s
2702 ft.lbf
And
3664 joules
The 180gr is more, just that, more, but then momentum and energy in terminal ballistics means nothing.
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30-11-2017, 19:41 #3
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Re: Lighter and heavy bullets-momentum
What the numbers don't tell you, is how the bullets will behave. Comparing weight retention, for example: The lighter mono should retain it's weight, and should be recovered with all of it's weight in tact. The heavier lead core bullet will shed a portion of it's weight, ending up much lighter, and maybe even weigh less than the lighter mono. The weight the lead core bullet sheds, is usually in the form of smal particles spreading out from the entry wound and that is what causes most of the blood-shot meat.
This is off course just one possibility of many. You should test your particular bullets in your rifle etc. and arrive at your own conclusion. This may or may not differ from mine, depending on many variables.
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30-11-2017, 19:52 #4
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Re: Lighter and heavy bullets-momentum
Trying to stay in my lane.
But the principles don’t really change from defensive ammo.
Energy and momentum numbers aren’t what matter. Performance is what matters. Momentum may or may not assist that.
But the difference in performance between is a monolithic 150gr and a cup and core 180gr and going to make a straight momentum comparison unreasonable.
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30-11-2017, 20:11 #5
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Re: Lighter and heavy bullets-momentum
I assume you are talking about advice given by the Doc.
In general terms and as a short answer he is spot on as would be expected.
The 308 is a very easy caliber to use effectively due to its moderate velocity.Your question was 'has the 150gr mono got the same potential as the 180gr lead cores'. I assume you mean the potential to kill a hunted animal quickly and efficiently....well yes ...both will work.On the face of it,both bullets will kill and it will not matter to the animal which of the 2 bullets was used.
Just remember that there are plenty of variables to be taken into account as far as hunting is concerned when it comes to terminal ballistics.If you start analysing bullet construction,impact velocity,bone penetration,meat damage,speed of death and a whole host of smaller factors,you are going to confuse yourself.
The chaps using fast calibers have more to worry about than you do.
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30-11-2017, 20:21 #6
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Re: Lighter and heavy bullets-momentum
As Messor,AR and BigT have said...a momentum comparison is pretty pointless due the different expansion characteristics of the 2.
As a broad generalisation the mono will penetrate deeper than a conventional cup and core bullet.As the speed increases,the difference becomes more obvious due to the conventional bullet not holding together.
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30-11-2017, 21:56 #7
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Re: Lighter and heavy bullets-momentum
Luckily I found the following article in a book series, some series called "how to for dummies", the specific book is called killing by bullet 101, and I quote :
Killing by bullet 101.
The only reliable measurement of killing power for a rifle bullet is the permanent destruction of vitals.
Section 1
Mono bullets vs cup and core penetration.
No mono bullet can out penetrate a heavier cup and core if the following criteria is met :
1: The heavier bullets retains more momentum.
2: The bullet expansion profile is the same, meaning the frontal surface are of the deformed bullet.
If the mono bullet retains more mass in the form of momentum then it will out penetrate a cup and core that looses mass in the form momentum and suffer a decline in penetration. Both a cup and core and mono bullet will suffer penetration according to the size of the bullet frontal expansion. The bigger the expansion the more drag on the bullet the less the penetration will be.
Section 2
Primary wound creation and penetration.
No correlation between penetration and primary wound creation can be found.
Meaning the penetration profile of the specific combo does NOT reflect killing potential. The only killing potential is measured in vital tissue destruction. So measuring a bullets penetration potential is of NO primary concern.
Secondary concerns of bullet penetration includes factors like external animal bleeding, meaning better tracking conditions, and of course over penetration, the wounding of secondary animals.
To sum up the use of each bullet type, monometal vs cup and core:
Monometal
The correct impact velocity must be determined to achieve or avoid the following :
1. Shooting the bullet too fast may result in the deforming surface area to shear off, be it petals or coarse copper material. The result of this would be a smaller primary wound channel but increased penetration.
2. Shooting the bullet too slow would result in speeds that are too small to invoke mechanical expansion of the deforming tip, causing the bullet to retain all mass and shape but a limited primary wound channel.
3. Shooting the bullet too fast could also lead to the fragmentation of bone, causing secondary particles that acts like a normal cup and core bullet shedding mass in the form of small particles.
4. Shooting the bullet correctly would result in the bullet both expanding to maximum possible diameter, but also penetrate enough to destroy the vitals. Without the unwanted velocity that creates bone shrapnel in the meat, causing meat damage in the form of bruising or bloodshot.
Cup and core
The correct impact velocity must be determined to achieve or avoid the following:
1: Shooting the bullet too fast where it loses a large part of its integrity resulting in poor penetration not reaching and destroying the vitals and meat damage in the form of bruising or bloodshot.
2: Shooting a bullet too slow where it doesn’t expand enough to create a maximum frontal surface area, which is required to create the primary wound path.
3: Shooting a bullet that’s got the expansion profile and speed to create a maximum frontal surface area and primary wound creation, in aqueous tissue, but lacks the strength to hold together when engaging heavy bone at higher velocities.
4: Shooting the bullet correctly would result in the bullet both expanding to maximum possible diameter, but also penetrate enough to destroy the vitals. Without losing too much structural integrity hampering ample penetration, whiles not causing unwanted meat damage in the form of bruising or bloodshot.
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30-11-2017, 23:40 #8
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Re: Lighter and heavy bullets-momentum
Yes, I did actually chat to the respected Doc. He , for bigger cartridges especially ranked the Northfork, then Swift Aframe, and a distance third the Barnes TSX in terms of what he has seen with regards to performance. Thanks for the reply.
Messor, very interesting and informative post. Sometimes I really think we overthink these aspects.
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01-12-2017, 07:42 #9
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Re: Lighter and heavy bullets-momentum
Cool. On the overthinking of things...it is great to investigate and find out what products are out there,how they perform and what will be best to suite your specific needs.
There is also a bit of BS floating around out there and the trick is to separate that from facts and not become overwhelmed with conflicting data which can cause you to second guess any decision you may make.
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01-12-2017, 07:51 #10
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Re: Lighter and heavy bullets-momentum
The way I see it.
Momentum is more critical if you do long range shooting at a target. Like a gong or paper.
For Hunting Terminal performance is important
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