copper tips help expansion?

[Jamtrails]

I'm about to embark on creating some bullets for subsonic hunting.

95% pure lead and 5% tin seems to be the alloy, but I wonder if adding copper would increase the expansion?

What I'm thinking of is a deep hollow point, and a tip with a shank that is short enough to leave some room for the tip to be pushed deep into the cavity to help it expand.

Has anyone tried something like this before?

[scooterwrench]

Copper is harder than lead so I'm thinking it would hinder expansion. Hollow points should get the job done.

[405grain]

A hard tip isn't necessary for expanding a hollow point bullet. The hydraulic shock alone is sufficient to cause expansion. If you want a more dramatic expansion you could even melt some bees wax and pour that into the cavity. On impact the wax will compress under terrific pressure and force the hollow point open. You should test this out on something before taking it hunting because the expansion might become too violent for meat harvesting. It might be handy for varmint bullets though.

[scooterwrench]

It might be handy for varmint bullets though.

Yeah,turns 'em into instant fertilizer.

[Winger Ed.]

A very soft alloy larger size hollow point will probably get you where you want to go.
Just enough tin to make it easy to cast. Even ammo makers have a hard time getting a hollow point to expand at slow speeds.

If the boolit isn't going fast enough to expand, you'd probably get the same results with a wide flat point that is less hassle to cast.

[mnewcomb59]

Copper will cause a work-hardening effect. Lead and tin are the same hardness the entire time they are mushrooming, and the mushroom is just as soft as the shank. Lead and tin will most often fold the mushroom against the shank of the bullet.

Starting at about 0.5% copper you will notice that your hollow points will harden as they mushroom, and then they do not fold back tight against the shank. I have seen that added copper usually means less penetration because you end up with a wider mushroom. I have also seen lead around 13 bhn ( 2.5-2.5-94.5 and 0.5% Cu) that you can scratch with your fingernail, but when you recover an expanded HP out of that same alloy you can't scratch the mushroom with your finger nail but you can scratch the shank and make a mark.

[405grain]

I don't think Jamtrails is talking about adding copper to his alloy. It sounds like he wants to cram a piece of copper into the hollow point cavity to force the bullet to expand.

[Mk42gunner]

I don't think Jamtrails is talking about adding copper to his alloy. It sounds like he wants to cram a piece of copper into the hollow point cavity to force the bullet to expand.

I think you're right. It sounds like the theory of the old Remington Bronze point bullets.

Some of the early British companies also did weird things with copper or wooden inserts to supposedly help expansion. Whether they actually did anything or not, I can not say.

As for sub sonic expansion, I don't think it will help; otherwise it would be used in just about every expanding handgun bullet on the market.

Robert

[beagle]

From my experiments on cast bullets in "whisper" subsonic loads, they don't expand at all. In fact, I shot some 457122HPs in the .45/70 and I recovered one, cleaned it, relubed and shot it a second time. All copper will do when induced into the alloy with toughen the outer skin and allow you to get 3-400 FPS more from an alloy without leading./beagle

[BLAHUT]

Wide flat point in pure lead will give you everything you are looking for, especially in subsonic loads, 100% energy transfer, pure knockdown. Can't get a better bullet in going slow.

[mdi]

In my early casting days I did a lot of "I wonder what would happen if..." thinking. I once thought of using a copper disc/cup on the nose of a cast bullet and how it would effect performance. A harder alloy smashing back against a soft lead bullet give some additional expansion?

[Jamtrails]

"I wonder what would happen if..." A harder alloy smashing back against a soft lead bullet give some additional expansion?

Yes! Not just harder copper smashing into the softer lead, but being forced down into the HP cavity like a wedge!

[charlie b]

We used to put a BB in the nose of HP bullets for this effect.

When the bullet is traveling at a slower velocity it will help open up the cavity. This is most evident when shooting through thick clothing, like a couple layers of denim. The BB keeps the nose from getting clogged up. BUT...a bit slower and the BB didn't help. So, getting a HP to open is still a matter of HP design, velocity and how hard the alloy. The BB just made the threshold velocity a little lower (100-200fps maybe).

We never tried it with long range bullets, just pistols at 25 and 50yds. At 50 we suspect it was starting to not fly as straight, but, it was not very conclusive evidence, just a slightly larger group.

[stubshaft]

Bac in the late 60's and early 70's, Remington had a line of J-words called Bronze Points. They were a bronze pointed cap over a jacketed bullet. The intent was similar to what you allude to but having shot a fair amount of game with them I did NOT find them any more efficient than the run of the mill core-lokt bullets.

[JSnover]

If you're looking for expansion, you're probably talking about medium game and you probably won't get it with a copper tip; you'll most likely get over-penetration.

[mehavey]

...subsonic hunting...

Go pure lead (you don't really need tin for decent fill-out)
and wide/flat point



postscript:
At true subsonic, however, significant expansion of any design will be "problematic"

Best option is go with "pre" expanded.

[fredj338]

Its all about hp shape. For lower vel, a wide/deep hp cast soft works great to 1000fps. At higher vel, either toughen the alloy up, a bit adding tin or change hp design. My higher vel bullets use a shallow/wide cup point cast moderately soft, 20-1. Exp is really good with little fragmentation.
I didnt see what caliber but a 270-310gr wnhp, cast 20-1, at 1000fps probably exits anything broadside,