Ratio of body to nose and nose size..

[Char-Gar]

I enjoy the 30-30 round very much and my current playtoy is a 1960 Marlin Texan carbine. With a good 170-180 GC bullet over 17/4759 it will give 2.5 MOA accuracy, plus or minus a tad depending on the bullet.

This Marlin has a land diameter of .305...Pretty large even for a Marlin. Yesterday I was shooting the above load over two 170 grain CG bullets and the results were just the same in terms of accuracy.

The first was a custom Mountain Mold with a nose that casts at .307.
The second is SAECO 305 with a nose of .303. Both bullets were sized .311 which is as large as the Marlin throat will accomidate.

One mold .002 over land and the other .002 under land. Both of these bullets are of the traditional 30-30 design with about a 58% body and a 42% nose.

I am left with one of two conslusions.

2) The smaller nose is slugging up to fill the bore
3) .002 nose undersize on a bullet that is 58% body does not affect accuracy.

I know accuracy would suffer with a .002 undersize nose on one of those long nose bore riders, but it doesn't seem to matter much on these "mostly body" bullets.

Any comments, corrections or experiences to share on the subject at hand?

[felix]

Charger, if your alignment is good and ignition is consistent, then the bore riding size of the boolit should not make that much difference, if any. Naturally, we are talking about a reasonable bearing length without regard for the nose being an extension. ... felix

[Bass Ackward]

I am left with one of two conslusions.

2) The smaller nose is slugging up to fill the bore
3) .002 nose undersize on a bullet that is 58% body does not affect accuracy.

Any comments, corrections or experiences to share on the subject at hand?

Chargar,

Two points are listed as 1.) and 2.)

Unsupported nose weight is unsuported nose weight. How much a bullet design can carry is limited by the bearing area of the caliber you are shooting and the maximum velocity potential of a weak bullet design.

It matters not if it is shaphed like a nose on a semi wadcutter, a spire point, or a bore rider that doesn't touch, for a rifle. Which by the way, a bore rider is nothing more than a semi wadcutter bullet for a rifle. It only needs to be elongated for weight. Let the nose touch the lands or add a DD band and you strengthen the design and improve the top velocity potential of the bullet.

What's the magic formula for bearing length to unsupported nose weight you ask? At what twist rate?

[Doughty]

Also for consideration is the "hardness" of the bullet.