why are cast bullets heavier for rifles?

[wileynet]

you are probaly getting tired of my posts, but ive noticed with cast bullets for rifles most are heavier than jacketed, is this a ballistic issue, or is it the trade for mass vs velocity, i tend to use 150 grain noslers with all my 30's(308, 300WM,30-06, 30-30) yet it seems most 30 cal start at 165 and go up, my previous post on the 303 i use 147 grain jacket but almost all cast bullets ive seen are either 180, 190 or 200  whats the reason

[Lloyd Smale]

heavier bullets penetrate better then light and in a rifle using cast you cant crank the velocity up much past 2000 fps no matter the weight so you might as well go with the heaviest bullet you can shoot accurately at those speeds.

[bilmac]

I was going to say the same as Lloyd. Cast bullets are limited as to the velocity they can be driven, but they can still have a lot of energy if you up the weight.

That said, I load some light weight rifle bullets to use as reduced loads. One of my favorites is the 30 cal. 120 gr Lee. I shoot them at 22 rimfire velocities. and they are accurate in all my 30 cal. rifles.

[.22-5-40]

Hello, wileynet.  I have found, for the most part, cast bullets which are heavy for the caliber shoot more accurately, than std. weight jacketed.  I say "for the most part"...I have used an original Ideal 311415 "squib" bullet in an 1898 Krag & 1903 spngf. with excellent 100yd. accuracy..this one weighs 170grs..while heavy..the Krag was designed for 220gr. roundnose jacketed.
  It might be because lead, being easier to engrave..hence lower pressures..a heaver slug allows the smokeless powder..which,  designed for jacketed bullets,  to build greater pressure for a more efficient burn.

[mcwoodduck]

Size for size a cast bullet is heavier than a jacketed because lead is heavier than copper.  The size of the projectile are about the same for your 30.  The copper clad 180 grain bullet will displace the same water as the 200 grain lead round.  If you look at the all copper bullets they are lighter than the jacketed counter parts for the same length bullet. 
 
 
 

[Anduril]

mcwoodduck, that's an interesting way of looking at the question, I like it.
Does anyone know how much of a typical 150 grain jacketed spitzer bullet is lead?
Or am I going to have to melt the core out of one and weight it myself 
..
 

[mcwoodduck]

mcwoodduck, that's an interesting way of looking at the question, I like it.
Does anyone know how much of a typical 150 grain jacketed spitzer bullet is lead?
Or am I going to have to melt the core out of one and weight it myself 
..

Depends on the design.
Look at a Swift A frame or Nosler Partition it is going to have more copper than a standard Remington Corelokt.

[Anduril]

OK, here's what I found in my own very unscientific sampling of two standard cup & core bullets by melting out the lead with a torch:
 
Hornady 6mm 100gr spire point - the jacket weighs 31 grains
Speer 30cal 165gr spitzer - the jacket weighs 43 grains
 
with these two at least, the weight of a jacketed bullet is around 70% lead and 30% copper/gilding metal
 
..
 

[mcwoodduck]

What if they fill the core with either tungstun or the heavier than lead metals like the Heavy shot.
A 308 bullet the size of a 150 would weight 165 and a bullet the size of a 180 woulod weigh almost 200 grains.
Heavier weight, smaller bullet, abble to be loaded with more powder as the projectile is smaller and could go as fast as the lighter bullets.  The opposite of the all copper bullets.
 

[max1138]

What if they fill the core with either tungstun or the heavier than lead metals like the Heavy shot.
A 308 bullet the size of a 150 would weight 165 and a bullet the size of a 180 woulod weigh almost 200 grains.
Heavier weight, smaller bullet, abble to be loaded with more powder as the projectile is smaller and could go as fast as the lighter bullets.  The opposite of the all copper bullets.

barnes tried that with the mrx line using tungsten I think, worked well enough but didnt sell many of em so it was discontinued, I think they were trying what you suggested to make their bullets shorter since their all copper bullets tend to be a bit longer than the standard lead core  style. I suspect enough people complained about the longer bullets eating up powder space but didnt really want to pay an extra premium on an already premium priced bullet. I never needed to buy any of them , the standard tsx  while longer actually helps me  reach the lands in my long throated single shots.

[Richard P]

  Among other things, rifle bullets that fill the throat and are large enough to benefit from guidance of the lands perform better. Rifles have come to depend on velocity to kill well whereas most handgun bullets rely on diameter to open wounds. Long bullets in handguns must usually fill the cylinder and they produce a good bit of recoil.  Rifles are heavier and that counteracts the recoil.     When considering changing to heavier metals for cores you must also consider their hardness. Bare lead alloys deform easily, jacketed bullets, while harder, are still able to deform due to the malleability of the lead core. If you replace the lead with tungsten as mentioned, you probably will have to reduce the pressure, or do as is done in the .45ACP barrels and use a very shallow land due to the jacket thickness. 
We get no ''free lunch'' in physics. Everything costs something in terms of energy.

[mcwoodduck]

What if they fill the core with either tungstun or the heavier than lead metals like the Heavy shot.
A 308 bullet the size of a 150 would weight 165 and a bullet the size of a 180 woulod weigh almost 200 grains.
Heavier weight, smaller bullet, abble to be loaded with more powder as the projectile is smaller and could go as fast as the lighter bullets.  The opposite of the all copper bullets.

barnes tried that with the mrx line using tungsten I think, worked well enough but didnt sell many of em so it was discontinued, I think they were trying what you suggested to make their bullets shorter since their all copper bullets tend to be a bit longer than the standard lead core  style. I suspect enough people complained about the longer bullets eating up powder space but didnt really want to pay an extra premium on an already premium priced bullet. I never needed to buy any of them , the standard tsx  while longer actually helps me  reach the lands in my long throated single shots.

Lead in pretty soft and will mushroom, I wonder if the tunston and tungston / Nickel mixes mushroom and what would be needed to make it expand reliably.

[max1138]

the tungsten was in the rear as a solid plug, picture a nosler partition with tungsten as the rear core and the front a standard mrx all copper bullet


heres a link
http://www.barnesbullets.com/products/rifle/mrx-bullet/

[mdi]

Not to be contrary, but, bullet molds for .30 caliber are available from around 100 grain to over 200 grain. I shoot 150, 160, and 173 grain lead bullets in my single shot 30-30...