PPB Intro
The Bullet
The Patch
Loading PPBs
Shooting PPBs
Reading Patches
Hunting & the PPB
Testing Loads
The GD PPB
The GD PPB
Experiment
Weather and
Black Powder
Hunting & Range
Estimation
Making a Pistol Grip
Email:
brentd@iastate.edu
The Gunn-Danielson Bullet
The Flat-based Variant
This bullet is effectively a Gunn 349c nose in a paper-patch form. It has the advantage of a short nose that should resist slumping during ignition and acceleration. It also has a very slight shoulder at the ogive that is intended to serve as a "delaminator ring". This ring is supposed to provide a consistent point for the inevitable formation of turbulent air flow along the side of the bullet. The ballistic coefficient of this design is about 0.46 at a muzzle velocity of 1350 fps. That is probably an overly optimistic velocity for my .45-100. I routinely get about 1280 fps in bullets of this weight and general configuration.
The Rebated Boattail Variant
The next bullet is identical to the bullet above but it has a rebated boattail. The boattail will dramatically reduce drag caused by the vacuum that forms at the base of the bullet. This is especially significant at subsonic velocities. Reducing drag is generally a good thing, but base drag does have the advantage in that it acts like fletching on an arrow, keeping the bullet stable and straight. Reducing base drag will then cause some decrease in stability of a long bullet. Thus, to regain this stability, the bullet must be shortened. In this case, Dick's calculations predict an optimal bullet length that results in a bullet weight of only 477 grs. Yet, it is estimated to have a an average BC over 1000 yds of flight of 0.59, with a starting velocity of 1350 (very realistic for my .45-100 and a bullet of this weight)! That's significantly better than most any bullet I've seen.
On note, this bullet uses a very large step for the initial rebate. This is a tooling consideration for a swaging setup. If you were to cut a mold for this, rather than a swaging die, you might wish to use a much smaller initial step.
Below are some charts that show the drag and Ballistic coefficients for both bullets. The top row is for the flat-based version. The bottom row is for the rebated boattail version. The left column is plots drag as a function of velocity and the right column plots BC as a function of velocity. All plots show a curve for a pure round nose version of the bullet and for a flat nosed variant made by lopping off the tip of the bullet to produce a 0.225" meplate.
This bullet is effectively a Gunn 349c nose in a paper-patch form. It has the advantage of a short nose that should resist slumping during ignition and acceleration. It also has a very slight shoulder at the ogive that is intended to serve as a "delaminator ring". This ring is supposed to provide a consistent point for the inevitable formation of turbulent air flow along the side of the bullet. The ballistic coefficient of this design is about 0.46 at a muzzle velocity of 1350 fps. That is probably an overly optimistic velocity for my .45-100. I routinely get about 1280 fps in bullets of this weight and general configuration.
The Rebated Boattail Variant
The next bullet is identical to the bullet above but it has a rebated boattail. The boattail will dramatically reduce drag caused by the vacuum that forms at the base of the bullet. This is especially significant at subsonic velocities. Reducing drag is generally a good thing, but base drag does have the advantage in that it acts like fletching on an arrow, keeping the bullet stable and straight. Reducing base drag will then cause some decrease in stability of a long bullet. Thus, to regain this stability, the bullet must be shortened. In this case, Dick's calculations predict an optimal bullet length that results in a bullet weight of only 477 grs. Yet, it is estimated to have a an average BC over 1000 yds of flight of 0.59, with a starting velocity of 1350 (very realistic for my .45-100 and a bullet of this weight)! That's significantly better than most any bullet I've seen.
On note, this bullet uses a very large step for the initial rebate. This is a tooling consideration for a swaging setup. If you were to cut a mold for this, rather than a swaging die, you might wish to use a much smaller initial step.
Below are some charts that show the drag and Ballistic coefficients for both bullets. The top row is for the flat-based version. The bottom row is for the rebated boattail version. The left column is plots drag as a function of velocity and the right column plots BC as a function of velocity. All plots show a curve for a pure round nose version of the bullet and for a flat nosed variant made by lopping off the tip of the bullet to produce a 0.225" meplate.
