If you found that they stabilized and shot well at low velocity, it might make a great subsonic, limited penetration load for something like the 300 Blackout?

you get the same 4' grouping with lead if your not doing things just so.

too much speed can cause corkscrewing then full instability and radical flyers if the C.O.R is off balance.
a more rearward c.o.g is why hollow pointing works to enhance accuracy in many bullets.
both [COG/COR] are something you have to take into consideration when designing a lead bullet.

this could easily be the problem, and the slower speed would remove the spinny issue causing the on target results.

quote:

Originally posted by Lamar:
you get the same 4' grouping with lead if your not doing things just so.

too much speed can cause corkscrewing then full instability and radical flyers if the C.O.R is off balance.
a more rearward c.o.g is why hollow pointing works to enhance accuracy in many bullets.
both [COG/COR] are something you have to take into consideration when designing a lead bullet.

this could easily be the problem, and the slower speed would remove the spinny issue causing the on target results.

Not shooting lead.

My test was trying to find if we can shoot these lighter bullets at higher velocities.

These weigh about 30% of copper bullets.

Using the same design as our copper bullets which shoot extremely well.

Saeed
You might want to take a look at the Miller bullet stability equation. It is used to calculate the stability factor of a bullet. It looks like if the dimensions stay the same then the stability factor changes linearly with mass. ie if the mass is only 33% of the original bullet then the stability factor will be 33% of the original bullet. The velocity factor is a function of the velocity to the 1/3 power. If this is the case you can not make it go fast enough to catch up. It looks like for a given velocity you would need a twist of about 5x whatever works for the copper bullet. You might want to try going the other way. Tungsten and uranium look good for this.
C.G.B.

I would love to try tungsten and uranium, but I don’t think my CNC machine would manage that.

Interesting experiment. Was there much aluminum fouling left in the bore? Like cgbach said, the light bullets might just need a much higher twist to stabilize. Do you have a higher twist barrel you could test? Making shorter bullets would also help the stability.

Very slight fouling as I coated the bullets with Tungsten.

Making the bullets much shorter will negate the whole purpose of the experience.

Might end up with a round ball!

My thoughts were to see if these lighter bullets can be driven at much higher velocities.

Saeed
Regardless of nonexistent accuracy how fast do you think you could get these aluminum projectiles to exit the barrel? Or would it be a risk to you chronograph to even try?

just a guess on my part, but I would guess that the twist in the rifling has a lot to do with it given the increased velocity...

I know there is a formula out there somewhere, but I can't recall where to go looking for it. and its not the one in Hatchers. It goes much deeper incorporating velocity into the equation.

quote:

Originally posted by Pa.Frank:
just a guess on my part, but I would guess that the twist in the rifling has a lot to do with it given the increased velocity...

I know there is a formula out there somewhere, but I can't recall where to go looking for it. and its not the one in Hatchers. It goes much deeper incorporating velocity into the equation.

Are you thinking of the Greenhill formula?
It includes diameter, bullet length, specefic gravity and density of the medium being shot through (IE air normally), but doesn't include velocity).
It indicates that an Aluminium bullet should require a twist rate about twice as fast as a normal cup-and-core bullet.

Is there another thread on this subject as I thought i had posted this link. Quite by chance I stumbled on an older video by Forgotten Weapons. The German engineers who developed the MG42 etc where working with CETME in Spain after the war and trying to develop a high rate of fire, long range infantry assault weapon and went the Aluminium bullet route. They ended up putting a copper jacket around.

Have a watch of this video and it has lots of pictures and diagrams on this subject from the early 1950’s

https://youtu.be/3Njddshr3n8

I had water hose with aluminum fittings and it became welded to my faucet. I'd not use aluminum in my gun.