55gr vs 62gr accuracy/penetration testing.
- Thread starter Hughgideon
- Start date
Lighter bullet = more velocity
more velocity = more kinetic energy
more kinetic energy = deeper penetration
Since Kinetic Energy = 0.5 • mass • velocity(2) squared
The difference in mass of the bullet has very little effect on the total kinetic energy
The difference in velocity however increases kinetic energy by the square of the delta velocity, much larger effect.
So it would be logical the faster but lighter bullet had more penetration, but if you had the exact velocities you would know for sure. The smaller groups could simply be a flatter and faster trajectory to the plate resulting in less environmental factors affecting the bullet. Match results have demonstrated conclusively that the slower twist rates produce better accuracy. at 3000 fps in a 1:9 twist, that will spin a bullet at (4000 r p s) 240000 rpm at 1:7 that becomes (5142 r p s) 308,520 rpm . Different bullets require different spin rate to optimize performance. Generally speaking with bullets of the same caliber longer bullets require more rpm to stabilize.
All of this is of course assuming the lighter bullet actually does have a higher muzzle velocity. You can try the test out at different distances and develop your own ballistic info.
Thanks for sharing!
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It's hard to say what's the energy at the target given the different muzzle velocities and the different ballistic coefficients.
It could very well be that the 55 grainer has more energy at 100m but conventional wisdom says the heavier bullet sheds less speed on the way.
...and the revs are a bit off (by a factor of 60)
Thanks! Yes RPM not r.p.s. So 4000 r.p.s. or 240,000 rpm and 5142 r.p.s or 308,520 rpm respectively
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Hughgideon
Member
Thanks for the feedback everybody. Some very informative posts. Admittedly my knowledge of the science behind this stuff isnt as in depth as it could be so this was some good food for thought.
Next time I'll try and remember to get the chrono out so I can toss up some real numbers on here. I'll also record some groups at some other distances and see if these results hold up.
Done.
Next time I'll try and remember to get the chrono out so I can toss up some real numbers on here. I'll also record some groups at some other distances and see if these results hold up.
There is a tendency to under estimate he power of the 55 gr bullet.
I shot some 100 lb + kangaroos with 55gr Hornady Soft Points and they went right through, leaving a fist sized exit hole. I was impressed.
I shot some 100 lb + kangaroos with 55gr Hornady Soft Points and they went right through, leaving a fist sized exit hole. I was impressed.
^^I too would like to see what the 62 greentip does to steel....
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