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The latest explanation of theory from Doc M (Michael McCourry) at MIB, quoted below:

A little more information, or theory, whichever.. concerning the Nose Projection.

As we see the comparison of the .458 caliber 325 gr bullets at over 2500 fps the longer nose projection really proves itself. I believe in the “Bubble” created by the big Flat Nose Solids………. The bubble is what the bullet rides in, and if the meplat is perfectly shaped and aligned the bullet rides for a long deep journey in its terminal state. Lots of things can disrupt the bubble during the ride, if the bullet is not perfectly designed.

Now, Nose Projection, one of the very last factors discovered. This can be two part, or considered in two ways, both leading to the same conclusion. The shorter nose projection makes the base of the bullet longer behind the nose projection. With this, I believe the bubble is collapsing on the base of the bullet, causing drag on the rear, perhaps collapsing just in front of the bottom band. While straight line penetration is not really effected, this drag slows the bullet faster and does not allow it to penetrate as deep. Now, the longer nose projection has a shorter bullet base, pushing the bubble out and around the base of the bullet, collapsing behind the base of the bullet, no drag at all…… deeper penetration.

Now, next step is very low velocity, lets just say less than 1800 fps for a starting point. If we take the 325 .600 longer nose projection and drop the velocity to close to 1600 fps, we find that it basically equals the depth of penetration of the short nose projection 325 at a much higher velocity of over 2500 fps…… We know that the higher velocity creates a bigger, longer lasting bubble, and with no drag on the longer nose projection the more velocity, deeper the penetration….



While the longer nose does penetrate some deeper at lower velocity, the amount of that is much less than the higher velocity, so velocity becomes a factor in nose projection as well, with both designs. However, less effect with the short nose projection from low to high velocity………



Now, lets look at some work done with the Short Nose projection 400 gr #13 Solid, Lever Solid………

Here we have a rather high velocity test at 2370 fps in the 1:14 twist rate 458 B&M. We see 40-41 inches penetration.



Here tested in 458 Super Short same 1:14 twist rate, velocity 1819 fps……… I don’t believe there is any substantial difference here, while the super short might be two inches more, I think that is more of a difference in test medium than anything else…….



And last a test in Sam’s double rifle at 1679 fps, unknown twist rate at test time……… and again, 40-41 inches of penetration.



Velocity has made no change in the 400 gr short Lever Nose Projection bullet. Perhaps ? the bubble is collapsing further up on the bullet base basically causing all to react the same? I really don’t know. Perhaps if we broke that 2500 fps mark with the bullet we would see some depth increases. We just don’t see it between 1679 and 2370…….

Now enter our latest new Solid, the 400 gr CEB #13 Safari, longer nose projection solid at 2300 fps……… Depth of penetration showing up with the longer nose projection, bubble collapsing behind the bullet, instead of causing drag on the base.



Now one might argue, or consider… why did SD not take over with the 400 Long Nose as opposed to nearly the same penetration with the 325 longer nose?????? Take a look at the VELOCITY……. The 325 started out at 275 fps faster than the 400……Still making SD the “Last” factor in solid penetration…….. Velocity trumped SD………