How soft does your alloy have to be to get hollow points to reliably expand?

[Good Cheer]

Definitely, much depends upon the design of the bullets' noses.
I'm a fan of gas checks on soft heavy castings with big hollows.

[curioushooter]

This is my experience exactly. Soft alloy works best. I usually worked with either 16:1 or 20:1 Pb:Sn. If I did use antimony it was balanced by weight with tin. I settled on an alloy of 96-2-2 as being optimal in 357 Magnum. Mushrooming in a solid is observed when you go past ~1400 FPS impact velocity. Antimony makes the alloy hard but brittle. Tin only adds a little hardness but doesn't diminish malleability.

[Winger Ed.]

I got in & out of making hollow points for .357 and .44Mag pretty quick about 20 years ago.
Not knowing any better, I cast them pretty hard. I was loading up to about 80% of max. published data.

Of the few I recovered from my berm, they pretty much just shattered down to the bottom of the hollow cavity.

Nothing wrong with HPs, I just found them to be a little more tedious to make for what I was shooting.
But they seemed to hit pretty hard. I got good clean kills on all the little black dots I was shooting,
and never left any wounded ones for the Target Cong to come back at night and drag off.

[Harter66]

50/50 WW tamper seals into dry powdered clay 1600 fps MV. .690 from .312 199.8gr minimum retention weight 196.5 gr most were 198+ . "Custom" Spitzer shape .....

[AnthonyB]

I'm a big fan of the cast HP, but don't shoot as high a percentage of them as before. My HP efforts have ranged from 9mm to 45-70, and I never worried about the petals shearing off. I just thought of sheared petals as the redneck's Partition.
The Cramer style moulds from MP make HP production almost as fast as solids, and I recently read that Eric at Hollowpoint will convert a HP mould to run on the Master Caster. That would make my HP use go up again!
Tony

[35 Whelen]

All these bullets are around 9 Bhn and cast of lead/tin only, 20/1 to 25/1, antimony makes them too brittle.


All the following bullets were fired into a water tub-

.32 S&W Long ~115 gr. HP, 835 fps-



.38 Special, 358429 162 gr. HP. Impact velocities are shown-



45 Colt-



These bullets are from game-

.357 Carbine, Mihec Carbine mold, 162 gr. 1800 fps MV, struck a hog at about 40 yds, stopped in the skin on the off side-



.44 Special SA, Mihec 429244 HP, 1105 MV struck a buck at 38 yds.-



.45 Colt SA Mihec copy of 45-270 SAA, ~265gr., 1040 fps MV, struck a buck at 48 yds.-



35W

[Indiana shooter]

I've had my best results from 20-1. If you add antimony, you risk the petals sheering if you don't properly match the velocity to your alloy.

With high velocity rounds (1800 fps out of my muzzleloader) my alloy is 50/50 + 5% tin. This alloy gives me reliable and devastating results down to about 1500 FPS without fragmentation. If I shoot a "magnum" charge over 2000 FPS I'm left with just the shank of the bullet and large fragments scattered all through the chest cavity of a deer.