The Gunn-Danielson Bullet

Below are drawings and descriptions of the bullet that Dick Gunn and I created. Also included are some comments that I included with these drawings that I sent to Richard Corbin, who built the dies and press to swage these bullets.

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.

Page 2: The Gunn-Danielson Experimental Boattail

This bullet is a 477 gr bullet designed for a .45 caliber Sharps cartridge. In my case, a .45-2.6" Shiloh Sharps. The object is to create a bullet that has a very high ballistic coefficient and relatively light weight thus creating a flat-trajectory with minimum recoil. The bullets below are swaged using a Richard Corbin press and dies custom machined for this purpose. The final bullet design varies slightly from the original drawings to accommodate machine and die durability constraints. But the concept still applies.

The lead in these bullets is about the equivalent of 25:1 hardness, and certainly could be harder. The swaged diameter is 0.443" and after patching, it is .450".

The photos below show the bullets before being loaded and after being shot into an oiled box of sawdust.

Bullets were fired as with the boattail completely bare as shown in the middle of photo 1 above. Only a thin sheet of newspaper separated bullet from powder. The idea here was that the base would experience equal pressure from the sides as well as the back, thus preventing base collapse. As you can see in the two right-hand bullets in photos 7 & 8, this did not work as planned. Not also, there is extensive powder peening on these bases as well.

The second method was a twist tail patch that covers the base but is otherwise the same. These I ended up shooting into a log instead, so they are not seen again in this experiment

The third method was to create a beeswax base for the bullets that would prevent the base from collapsing. This is shown in photo 1 above to either side of the bare based bullet. This method was quite successful, however loading them is about as much fun as pulling teeth and only one of the two experimental bullet resulted in a shootable bullet. The bullet however, looks pretty good. It's the third bullet from the left in photos 3-6 & 8; it is the second fully visible bullet in photo 7. In all photos, the bullet immediately to the right of it is an unpatched and unfired bullet for comparison. By my measuring, the base shortened about 0.004" and swelled a bit less. Nearly identical to it's shape prior to launch. There is no powder peening in this bullet because a 0.06" veg wad separated bullet and powder.

One other curious thing about this particular bullet. The shaft of the bullet just ahead of the boattail rebate seems to be flared. Almost as if it's skirt is being blown up. Not sure how this can happen but it certainly did. Also, you will just barely make out the "delaminator" ring or ridge at the ogive. This is very very slight on an unfired bullet and I thought it might be lost when the bullet obdurates but it's not. At least not entirely. It would probably be more visible if the bullet were not so badly eroded by the sawdust. So, at least this part of the new design looks promising.

What could be done next? Well, a harder alloy is likely to be the most popular suggestion. It might work, but I don't think it will negate the need for a wax sabot on the base. And you might notice that the bt bullets barely show any engraving by the rifling while the 550 gr pure lead bullets do show rifling quite conspicuously. This is a lot more obvious when you can hold the bullets in your hands. So, harder lead may save the base, but it won't produce the obduration necessary to engage the bullet fully. Of course, if I were to use groove+ diameter bullets, this might not be a problem, but I don't and probably won't because to do that right requires new dies. Thicker paper could provide a weak alternative but it has other liabilities.

The other bullets in the test where a flatnosed LSWC of 550 gr and a Sharps Long Range Bullet, also 550 grs. Both bullets were pure lead and with cupped bases. The cupped base on the FN LSWC was well preserved. But the Sharps bullet obviously tumbled in the box and did not show much of anything useful, which is too bad since I wanted to see if the nose slumped as I suspect. First, I have to recover a nose :(.

Finally, a last comment on catching bullets. This is NOT fun. It's a royal pain in the keister to find these, even with newspaper dividers to give you clues as to where to search (no, I don't have a metal detector but I wish I did.) One of the Sharps bullets never was found. Further, it appears that the bullets are somewhat deformed from misc. chips or whatever in the dust. This was pretty fine dust and but a few chips of bark, leaves, etc made it in and that was plenty to disfigure even hardened lead.

Sawdust box - round #2 26 Jan 02

I shot a couple more bullets into the sawdust to check on a modification of the above loading method. This time, I loaded and compressed 100 grs of Goex Cartridge powder into each case, followed by a 0.06" think John Walter's veggie wad and then 0.150" of extruded SPG lube. The bullet, wrapped only from the ogive to the rebate at the forward end of the boatail, was then seated onto the SPG and squeezed down with my thumb. This caused the SPG to flow just enough to perfectly encase the boatail. Removal of the bullet was easily possible to confirm a perfect cast. There was still substantial grease cookie behind the bullet so that on firing, pressure would fill the area around the boattail before the card wad began to crunch the base. Indeed, perfect hydrostatic pressure was attained. The two photos show perfect boattails after extraction from the sawdust. Only one chronograph reading was made and it suggested 1411 fps. Yet, the BT is perfect.

In the photos you can see that they look much better than the photos above. Further, by taking an unfired bullet (center bullet in each photo) and putting its base next to the fired bullet's rebate rim, the base of the fired bullet comes exactly to the rebate rim of the unfired bullet. In other words, the boattail is exactly as long as it was when it was loaded.

Further, I tried inserting the base of the fired bullet into the base punch that made it. A perfect fit. If the boattail had swelled and/or shortened, it would not have fit properly. Finally, there is a tiny pimple in the base punch as a result of its being made on a lathe. That pimple makes a tiny dimple in every bullet's base. The pimple, though not easily visible in the photo - is easily visible with the bullet in hand.

So, in short, I now know exactly how to load these things. It's time to see if they can be made to fly straight.