....continuation of this thread that segued into discussion of Bell's 7x57 "elephant" bullets.
I was finally able to scrounge up enough phone books to do the test today. I pulled one 173 gr nickeled FMJ roundnose bullet from an old military FMJ cartridge. Re- loaded with modern brass, powder and primer to about 2300 fps muzzle vel to simulate a close range (elephant) impact velocity. I used an M1895 Mauser 7x57 for the test. DWM 173 gr 7mm bullet/ammo at this velocity is what Bell used and wrote about.
I used the same 100% water saturated bundled phone books in a trough as the primary test media as I always do for consistency and comparison of results. Behind the 1st 4" bundle, I placed a 1 3/4" wood board to simulate bone. At the end of the trough I place a dry sand "stopper"... just in case. Total length of media for this test was 42" I learned the hard way that certain bullets may not stop in that length no matter how tough this media is. Normal maximum penetration of most all
expanding bullets like TSXs and A Frames at normal impact velocities and of common weights from the 270 cals through 458 caliber is about
20". I learned that a 458 cal monolithic flat point of good design, like a GS Custom
Flat Point Solid, at about 2200 fps will not stop in over
45" of this test media.
I lined up the bore so the bullet travel axis would be in low center alignment with the media axis. The bullet penetrated in a perfectly straight line up until about the
25" mark. At that point it began turning sideways and traveled sideways (not tumbling) until it came to rest about 3" into the dry sand "stopper" at the end of the trough. The distance of the turn to sideways was approx. 5" of travel. The probable cause of the instability and yaw sideways was loss of rotational/gyroscopic stability due to friction. From the 5" zone of its directional veer off axis, it continued in more or less a straight line and ended up sideways in the sand. Similar tests of modern spire point FMJs in this same media show a slightly different reaction. Their track after instability begins is noticeably curved and tends to have a much greater dispersal from the flight line axis- often times exiting the trough box or media all together.
The bullet shows some scuffing/abrasion of the nickel plating from it's travel through the bore, the media and shows sand blast pitting on one side from contact with the dry sand. That indicates the bullet was not spinning when it contacted the sand. The bullet's track print through the layers of paper show it did not tumbler once it went unstable and veered off course. It simply yawed sideways and stayed that way for the rest of its penetration and was laying sideways in the sand about
2-3" off axis from it's original path of travel. The bullet was slightly bent at about its midpoint. I would guess that occurred immediately after going unstable at the
25" mark as that would have been the zone of maximum dynamic stress on the bullet. Total penetration of this bullet approx.
40".
Some pics of subject cartridge and bullet, test media trough, recovered bullet and hand sketched diagram of results.