At the risk of reviving a dead horse, I had anther thought on the topic:When you fire a 8 lb .308 Winchester hunting rifle, the gun and the bullet have about the same momentum (Actually, the rifle has a little more because of the mass and velocity of the ejected propellant gasses). However, the bullet carries about 2500 ft.lb at the muzzle; while the rifle carries only about 12 ft.lb.If momentum predicted penetration, then no one would volunteer to shoot a hunting rifle more than once. Thus, it is clearly the ratio in FPE between the projectile and the gun that makes shooting something useful. As in, punching a hole in the target, rather than puncturing or dislocating your shoulder.Now, you may be asking if a lighter faster projectile would penetrate clay or ballistics gel further, than another pellet of a similar caliber, when the second projectile is heavier, but travels proportionately slower? In that case, the heavier projectile may very well penetrate deeper because it is going slower. This is because drag against a body travelling at high speed through a fluid is exponential with velocity; rather than because momentum is more useful than energy.You might care to test this out; using different projectile weights of the same caliber and form; shot at velocities that normalize first, energy; then momentum. For sticky viscous materials, such as soap, clay, ballistics gel and flesh; reducing the velocity by adding mass should increase penetration. That is, unless the projectile was already moving so slowly that the lack of energy was limiting penetration...
But, the .22-250 was pushed too fast for the bullet to hold together. Any soft point or even thin jacketed bullet pushed that fast into clay will come apart. FYI- ballistics coefficients for 30-30 bullets not so good
Now, lets see what happens with those tests, shooting copper solids from every weapon.
And another edit- at most airgun velocities, fragmentation is not much of a factor.
Quote from: Bryan H. on October 19, 2018, 09:56:49 PMAnd another edit- at most airgun velocities, fragmentation is not much of a factor. Nielsen Specialty Ammo may beg to differ Look at the expansion of the NSA slugs in the video. If these hit a larger animal or heavy bone, they will fragment...
Found some interesting data here: http://www.brassfetcher.com/Airguns/177%20Caliber%20Airgun.html not sure how they got all the intermediate velocity data. It will take a bit of time to work through all of it.
The brassfetcher velocity/penetration data is very interesting. First; I have pasted the graphs for the two general types of penetration behavior, based on pellet velocity directly below:Non-deforming round ball (BB) penetration appears very linear with velocity. Both increasing the velocity and mass (lead VS steel) increases penetration proportionately. Thus, penetration is proportional to projectile momentum for robust projectiles of this shape:The link shows the penetration VS velocity graphs for a number of other pellets. The RWS wadcutters graph below demonstrate how pellets that are or become blunt (deform) behave with increasing velocity. This tendency for penetration to increase with velocity, then to drop off sharply after peaking includes "round nose" and "sharp point" pellets, that do not have (hemi)spherical heads (with tangent nose radii).The consolidated data graph below indicates that the 8 grain lead BB penetrated better than the 8 grain round nose diabolo pellet. Here, momentum appears less important than form (or deformation at higher velocity):Considering the above, you might say; "we are both right"...
The roundballs do not deform at the velocities used, so penetration is proportional to velocity and SD (ie momentum)
IMO 8-10% correlation with theory on single tests is pretty close.... If you tested 10 shots, and then drew a trendline through all the datapoints it may well be even closer.... It is interesting that the steel BB has a slight edge, whereas if higher velocity was a detriment (as suggested earlier) it should be the reverse.... There is a good possibility that the diameter of the BBs are not identical either.... The steel BB has to be small enough to pass along the lands, whereas a lead roundball may well be large enough to engage the rifling.... We would need to know both the exact diameters and weights before trying to nitpik that last few percent....I can't take credit for the "Penetration is proportional to SD x Velocity" formula.... It comes straight of the Penetration calculator used in ChairGun…. However, the testing I have done seems to follow it pretty closely.... certainly close enough when you consider the different densities of an animal that a pellet/bullet encounters....Bob