Difference between cast an jacketed

[GSPguy]

So what makes a cast bullet different from a jacketed besides the jacket?

I have often wondered why a proven bullet design like a 168 gr SMK would not shoot well from a mold that mirrored the jacketed bullet.

Is it just the hardness and resilience of the jacket?

It seems like one could mix an alloy to come close to the hardness of the jacket.

I am sure there is a simple answer but I don’t know what it would be.

 

[Tom]

I'm probably the furthest from an expert here, but the jacket contributes a bunch to stiffness and a cast Spitzer design tends to slump upon firing since it has such a long portion that is unsupported by the barrel.

 

[Brad]

No way to get a lead alloy as hard as a copper jacket.
Jacketed bullet can handle some misalignment with the bore, doesn’t deform as easily under pressure, and doesn’t suffer nearly as much from gas cutting.
Also, to get that hard would require significant Sb content and that makes the bullet brittle.

To me the key is to use designs that balance the nature of cast bullets instead of fighting them. So much happens in the first few milliseconds after the hammer drops. Going with the flow is your best bet.

 

[Rick]

Also, the copper jacket is far stronger than any Pb alloy and can take the rifling with much higher pressure without skidding and shearing.

 

[BudHyett]

So what makes a cast bullet different from a jacketed besides the jacket? - 1) Cost. 2) Ease of home manufacture. 3) Basic design to have a flat base. 4) Ability to shoot old, odd bore size calibers.

I have often wondered why a proven bullet design like a 168 gr SMK would not shoot well from a mold that mirrored the jacketed bullet. - The lead bullet requires more body to land and groove contact to align and spin the bullet. The boattail base allow the powder gases to move into the narrow gap between the body of the bullet and gas cut the bullet seriously affecting both precision and accuracy.

Is it just the hardness and resilience of the jacket?- Basically.

It seems like one could mix an alloy to come close to the hardness of the jacket. - No, the bullet becomes brittle far before achieving this hardness.

I am sure there is a simple answer but I don’t know what it would be. - There are no simple answers.

 

[bruce381]

Also a jacketed bullet will not have any or should not air pockets from the forming swaging process making more accurate or repeatable.

 

[Ian]

You have to look at the bigger picture here, and that has to do with DYNAMICS.

You can in fact make a mostly lead alloy as hard as gilding metal jackets, but then it lacks two things: Malleability and surface friction characteristics. Jacket fouling is a whole thing that arsenals around the world worked diligently to mitigate and it took decades to get it right. A solid gilding metal bullet is a Barnes, and the early versions fouled like crazy for several reasons including the alloy type used so it would split and mushroom instead of fragment, and lack of grooves for the alloy displaced by the lands to go.

A jacketed bullet has a jacket alloy tuned to slide down the bore, take engraving forces and displacement without getting bent into a banana, and it has a soft, very ductile core which allows the bullet to draw lengthwise as it engraves. Solid Barnes bullets now have deep grooves for the metal to squish into and some have anti-friction coatings. A cast bullet made as hard and tough all the way through as a bullet jacket just isn't a real good idea as it will lead like crazy due to land abrasion and frictional heat at high velocity.

Oh, but powder coat a 10 BHN cast bullet with .002" of polyester paint and the whole game changes.....

 

[RBHarter]

Nose slump , centrifugal force resistance ........

 

[Bret4207]

This is one of those questions that was asked 100 years ago, tried for 50 years and in the end it all proved they are more different than alike. I don't believe "gilding metal" (brass and zinc) is used for bullets anymore. It's more copper than anything else and has been since the WW2 era IIRC. The differences? Ability and design to handle pressure is what it comes down to.

 

[358156 hp]

You have to look at the bigger picture here, and that has to do with DYNAMICS.

You can in fact make a mostly lead alloy as hard as gilding metal jackets, but then it lacks two things: Malleability and surface friction characteristics. Jacket fouling is a whole thing that arsenals around the world worked diligently to mitigate and it took decades to get it right. A solid gilding metal bullet is a Barnes, and the early versions fouled like crazy for several reasons including the alloy type used so it would split and mushroom instead of fragment, and lack of grooves for the alloy displaced by the lands to go.

A jacketed bullet has a jacket alloy tuned to slide down the bore, take engraving forces and displacement without getting bent into a banana, and it has a soft, very ductile core which allows the bullet to draw lengthwise as it engraves. Solid Barnes bullets now have deep grooves for the metal to squish into and some have anti-friction coatings. A cast bullet made as hard and tough all the way through as a bullet jacket just isn't a real good idea as it will lead like crazy due to land abrasion and frictional heat at high velocity.

Oh, but powder coat a 10 BHN cast bullet with .002" of polyester paint and the whole game changes.....

In order to quantify powder coating in my tidy little mind I've taken to comparing it to surface hardening, which itself doesn't work with lead, we've tried it.

 

[Ian]

In order to quantify powder coating in my tidy little mind I've taken to comparing it to surface hardening, which itself doesn't work with lead, we've tried it.

Think of it more like Teflon coating.