Denser bullet=more pressure?

[deserthntr]

i didnt want to hijack andy's thread so i started a new one. i now understand that because of a denser bullet you cant use another bullets reload info, but i dont understand how the denser bullet causes more pressure. does it contact more of the barrel causing more resistance and therefore more pressure? or does the bullet not "give" as much and so it resists the explosion more as opposed to indenting in a little and causeing less pressure? thanks

[azslim]

It's not the denseness as much as it is the ogive, length and base that can/will result in different pressures.

[andygrand]

http://www.frfrogspad.com/intballi.htm

 

Here is a decent link that talks about internal ballistics and will give you a better idea of how it works.

[Benbrown]

The two things that determine velocity (given the same powder charge) are mass and friction. For conventional bullets, pure lead bullets are the densest for a given weight. There are alternatives to pure lead, one of which is a tin/tungsten/bismuth alloy that can be cast anywhere from 80 percent to 110 percent as dense as lead. Thus, a 180 grain bullet with a TTB core and a cupro-nickel jacket can be made shorter than the same bullet with a lead core. Theoretically, the TTB bullets can be used in rifle barrels with a slower twist. As the proportion of copper or gilding metal in a bullet increases, the mass decreases given the same overall length. Pure copper bullets such as the Barnes offerings, are pretty much the least dense of the commonly available center-fire rifle bullets.

 

Friction varies with the composition of the bullet jacket, the total bearing surface of the bullet and the finish of the barrel. In the same barrel, a copper bullet (such as the Barnes) or one with a pure copper jacket (such as the Swift Scirocco and A-Frames) are "grabbier", i.e. their jackets will develop more friction between the bullet and the barrel, resulting in a decrease in velocity with equal powder charges. Friction can be reduced in these bullets by adding a longer ogive (the sloping nose to the point of the bullet) and a boat-tail to reduce the bearing surface. The grooves in the Barnes TSXs and TTSXs (as well as the Nosler E-Tips and Hornady GMXs) are there to not only reduce friction, but also to give the copper (or copper alloy) that is displaced by the barrel lands someplace to go, also reducing friction.

 

This is a somewhat simplified explanation, but still generally correct in most instances.

[deserthntr]

Awesome thanks guys. I got it all now