A man marries a wife. He does not marry her sister, nor her other sister, nor her brother. He does not marry her high school friend who was “nearly identical,” and he does not marry any of a half dozen high school or college girlfriends which were all of the same “type,” but obviously individually different.
Explain why this man married this one person out of the 10 others also mentioned which are quite similar —> therein, you will have your answer.
For the context of our conversation here discussing 50-55grn bullets, twist rate is dramatically overhyped, including so in this thread. Between 50-55grn bullets, there’s no choice in barrel twist which is correct for one end of this narrow spectrum but wrong for the other.
So what you’ll find are wholly subjective preferences of nearly intangible differences in bullet performance. As an example, there are 3 common Hornady V-Max’s, 50, 53, and 55. Many predator hunters favor the 55 because of the extra tail mass, claiming the heavy flat base penetrates better than the other two. Some longer range Varminters favor the 53 because of the increased ballistic coefficient largely drawn by the boattail. Still others, like myself, forego these nearly-tangible objective advantages for the other two and shoot the 50 v-max solely because it is so widely available and at such low prices - and still effectively does the same thing as the other two in the field. Why do I shoot the 50 vmax over the 50 or 55 BST or NBT? Eh, why did the man marry the one woman?
Also for reference:
@Daniel craig’s description above regarding Force = mass * acceleration is largely misapplied here. First, cartridges do not produce a fixed net force, they only live under a relatively fixed maximal force. The same cartridge can be loaded to the same maximal force - same pressure - with two different loads, but yield exceptionally different net forces, net accelerations. What he should have been describing is a relationship between potential energy (powder charge) and kinetic energy, and the resulting Work done (kinetic energy before impact minus kinetic energy after, minus losses), which are largely quite difficult to quantify, but easily described qualitatively.
In real-world, inelastic collisions - such as a bullet hitting a target, especially game animals - MOMENTUM is conserved. P = mass * velocity. This largely describes why light, fast bullets kill so well at close range, but then lose ground to heavier, slower billets at long distance - the light, fast bullet loses speed and resultingly momentum at range, whereas higher BC, heavier bullets hold momentum at range better.
So in a relative case where approximately the same powder charge is able to be used (simplifying here) under two different bullets: PE1 = PE2, so and assuming the same combustion efficiency KE1 = KE2, but using a 50grn bullet in one load and a 70grn in another (the proposed 20grn difference). Not wasting breath with conversions, just getting to palatable scale numbers:
A 50grn bullet at 3200fps yields 1136ft.lbs. kinetic energy (KE1), which we’ll also apply to the 70grn bullet (KE2). Back-calculating out, a 70grn bullet with 1136ft.lbs. is traveling at 2704fps.
So the momentum - the conserved aspect of the impact - for these two:
50grn at 3200fps (divided by 7000grn/lb) = 22.9 lbm ft/sec
70grn at 2704fps (also divided by 7000) = 27.0 lbm ft/sec
So the 20 grn heavier bullet is hitting the target with 18% more momentum. This is why 70 grain loads hit harder than 50grn loads.
(Recognizing actual charge weights for heavier bullets, the potential energy, is typically lower due to the increased inertial moment - “back pressure” - in the early ignition, but simplifying the case for the explanation).
