curious

[XWrench3]

i have a question to ask. besides tradition, it seems to me like it should not be. has anyone else ever wondered why cast boolits are not anywhere near the balisitic coefficient that "J" bullets are? i understand, that back in the old days, most people really did not care, or think about it. a boolit that was accurate, at a decent hunting range, was good enough. and they accepted this as part of the technology of the day. but that was then, and this is now. this is 2011. we have the technology to put the gettysburg address engraved onto a pin head. it seems to me we aught to be able to cast rifle boolits with a b.c. around .500 or so anyway. is it a difficulty to cast a long thin nose issue? i understand that we can not crimp a gas check to a boat tail, but it seems to me like we should be able to cast a much more b.c. freindly boolit. if for nothing other than target practice. or are we doing things the way we have been doing them for 150 years thing?

[44man]

Several reason I guess. Many cast were made for lever guns, big bores and handguns.
Then some boolit designs are prone to slump or bend when shot.

[sqlbullet]

Then some boolit designs are prone to slump or bend when shot.

This.

A long unsupported nose which will give those kinds of high BC's will slump when accelerated to a high velocity. It is not a limitation in our mold making or casting ability, it is a limitation of the characteristics of lead and lead alloys we use in bullet casting.

Bismuth or zinc bullets may fare much better with different designs since they are markedly stronger than lead alloys.

There may be some application for a different design in low velocity, low drag cartridges like the whispers. A long nose 30 cal my do well.

[GrizzLeeBear]

The high BC bullets get a lot of the BC from the boat tail and the long tapered ogive. Two things that are hard to do with cast.

[XWrench3]

The high BC bullets get a lot of the BC from the boat tail and the long tapered ogive. Two things that are hard to do with cast.

i do not see where a boat tail design would be a problem. there are many bevel base pistol bullets. the nose shape should not be an issue as far as casting goes either.


A long unsupported nose which will give those kinds of high BC's will slump when accelerated to a high velocity. It is not a limitation in our mold making or casting ability, it is a limitation of the characteristics of lead and lead alloys we use in bullet casting.

i can see your point. i never thought about the nose distorting during acceleration. do you think this would happen with 100% linotype?

[stubshaft]

Bevel base pistol boolits are designed for low velocity applications and to ease loading.

I don't think that you could drive a plain based boat tail to a sufficient velocity where the BC would be of any concern.

[Bret4207]

The lack of support, tendency to slump, lack of balance, loading issues...all work against long pointy boolits. The GC would just be more issues. If you want a high BC stick with jacketed.

[stubert]

cast are generally held to less than 2000 fps or so. Having a high BC wouldn't matter as much at low velocity like it would on a 3000 fps round.

[montana_charlie]

it seems to me we aught to be able to cast rifle boolits with a b.c. around .500 or so anyway.
We can...

What is gained by having a bullet with a high B.C.?
It retains more of it's original muzzle velocity so it requires less elevation to keep point of impact centered.
It is more aerodynamically stable, so it bucks wind better...meaning it takes less windage adhustment to stay on target.

What factors determine B.C.?
Bullet shape combined with bullet speed.
A slick, pointy bullet can only achieve it's designed B.C. when it is driven at high speed.
A bullet that can only travel at low speed will have a better B.C. if it is not 'pointy'.
A bullet which must do most of it's traveling at or near the speed of sound will benefit from having a nose tip that is 55% of bullet diameter. That ain't 'pointy'.


This is the Money bullet in a paper patched configuration. Diameter is .454", and length is 1.450" The nose tip is a .250" sphere which blends into a tangential ogive whose arc radius is about 4 calibers. The cylindrical portion (the rear half) is .750" long, with the remainder being the 'nose'.

http://castboolits.gunloads.com/picture.php?albumid=88&pictureid=1210

To answer the original question, this bullet has a B.C of .571 when driven at 1350 feet per second.

Looking carefully, you can see that the nose on the fired bullet is a bit fatter than the others. That shows the nose 'slumped' when fired because the alloy was too soft. Because it slumped straight back (due to excellent alignment with the bore) it was an accurate shot at 100 yards. But, it would not have fully reached it's top B.C. potential due to the 'modification' during firing...therefore it would have struck low on a long range shot.

CM

[geargnasher]

CM, that's excellent! Thanks for sharing.

Gear

[felix]

MC, an excellent picture!!!! Thanks. ... felix

[felix]

Dang, Gear, we must be competitors, even by accident!!! ... felix

[mpmarty]

In addition to shape determining BC the sectional density matters also. Like an arrow has high sectional density and so penetrates well. Sectional density is weight divided by diameter.

[geargnasher]

Dang, Gear, we must be competitors, even by accident!!! ... felix

[smilie=l:

Gear