Nose Projection Above the top Band of Bullet
The last discovery concerning terminal penetration of solids was the "Nose Projection" in front of the first bands of the bullet.
Many BBW#13s were tested for various big bores, calibers, and cartridges. Most of these being designed for Bolt Action rifles. Cartridge length, magazine length played an important role in feed and function, and in the length of the "Nose Projection" out of the various cases. For the most part the length of the nose in front of the top bands was from .600 in the B&M Super Shorts, to .700 in the larger B&Ms and various other big bore cartridges.
However, for the lever action rifles that Nose Projection had to be much shorter, down to .450 or less, for it to work in most lever guns. For many 100s of tests I kept noticing that depth of penetration was considerably less than what I would have expected of the same weight or caliber bullet. Even tested at higher velocity in bolt rifle cartridges, there was no difference or little difference in depth of penetration. On average these shorter nose projections were given 25% less penetration than what I considered normal.
Finally it dawned on me what was happening. The light bulb came on!
One of the reasons a properly designed flat nose is successful is that upon terminal penetration in aqueous material, or animal tissue, is that the flat meplat creates a "Bubble" in which it rides in during penetration. Any disturbances in that bubble creates instability, or effects depth of penetration.
The Short Nose Projection was allowing the bubble to "Collapse" on the rear of the bullet, instead of behind the bullet, creating drag! Because the BBW#13 Solid has a proper 67% meplat, radius edge, and overall properly designed, it still remains stable even with a short nose projection, however, depth of penetration is effected because of the drag on the base of the bullet.
Since this discovery Nose Projection has become a very important factor in design. With bullets designed for Lever Actions, there is not much one can do on this front, other than understand the effects of Nose Projection.