Where is the lead?

Guy Miner

Master Loader
Apr 6, 2006
17,453
4,514
Have been meaning to ask this...

Here's a .30 cal, 165 gr Nosler Partition I recovered from the water jug testing:
IMG_4783.jpg


Here's a .25 cal, 115 gr Nosler Partition I recovered from the water jug testing:
IMG_4786.jpg


Notice that on the .257" bullet, the lead no longer extends all the way back to the end of the bullet jacket. What happened to it?

Burned off when fired?

Destroyed somehow on impact?

Shoved forward in the jacket on impact?

What do you guys think?

Muzzle velocity on the .30 was about 2750 fps and the .257 was moving 400 fps faster at about 3150 fps as I recall.
 
Notice how the rear section has "toadstooled" under the Partition between the cores? The rear chamber has mashed outward around the midsection (I call it toadstooling rather than mushrooming just to keep the terms separate) and the internal volume of the rear chamber has increased due to reshaping and stretching of the copper jacket. The lead has just done what dense objects do, following the laws of inertia. That lead body in motion tended to remain in motion a little longer than the lower mass copper body containing it, and so it appears to have lost some lead.

This is why I like to consider both kinetic energy and momentum when choosing a bullet. KE is mass x velocity(squared) where momentum is just mass x velocity, showing a greater emphasis on mass than KE. Your results give a visual of it. Consider if we think of the bullet striking an animal. It will tend to stay in motion while moving through the animal, also. And a heavier bullet (larger mass) will have a higher tendency to remain in motion. SD really is a good measurement of this, as well.
 
Guy, the same basic thing happens when I fire 140gr PTs from my 264WM into water jugs at 3200. They look pretty similar. I think it is the lead pushing forward into the PT. The PT can't go anywhere so it spreads out. Still looks pretty good to me after such a torturous entry into close range jugs. Scotty
 
The phenomenon can be explained by compression of the lead and partial rupture of the mandrel resulting from the exaggerated force of impact due to non-compressibility of the water.
 
Exactly what I was thinking. The bullet, at over 3,000 fps, slams into the water and instantly starts a very harsh deceleration. Bullet gets mangled a bit, and the lead pushes forward, any way it can.

Interesting stuff. Also interesting to me is how nicely the heavy base of an AccuBond or a Ballistic Tip hangs in there, with no deformation.
 
That 25cal PT looks pretty darn good considering the impact velocity.
I'll bet that would really stroke a deer.
 
Guy

I hace had this happen on even the heavy 338 cal PT's. The high velocity impacts causes the rear core to rivit.

JD338
 
If you ever notice a swift A-frame bullet it looks like it is impregnated at the Partition section because of the lead moving forward.
That is an exaggerated state of what happens to a NP because the SAF has a bonded front so it does not break off like the NP, hence way more resistance on the SAF.

2036FP_SwiftAFrameRifle_BulletCutawayUpset_PG.jpg
 
The TBBC's seem to do the same thing. I have a 225gr TBBC recovered from my old mans Brown Bear that looks just about the same. Pretty danged tough bullets we have nowadays! Scotty
 
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