What do we really know about the transonic zone?

[Semtav]

I used to know how to computer generate the shape using that formula and sites available on the internet that you just plug them in to.
Obviously a few brain cells have escaped in the last 6-7 years.

I have no idea whether it would be a feasible nose. just something I was trying to experiment with

[Distant Thunder]

While looking for something else on my loading be this morning I found this, the rocket bullet.

It is 1.458" long, .444" in diameter and weighs 488 grains.

In the little bit of testing I did it shot well, but not better than other bullets and it was light for the caliber so I never did anymore with it. I had cut the mold for a friend and I believe he still has it.

The formula used to generate the nose shape is supposed to be something the aerospace people had developed for transonic rocket nose cones.

I personally prefer my bullets to be less pointed and a bit heavier.

[Semtav]

So what variables do we have when trying to alter our bullets performance in the transonic range?

1.nose shape
2.bullet length
3 bullet alloy
4.twist rate
5.muzzle velocity.

am I missing anything ?

[Distant Thunder]

I think that not only is nose shape important in the transonic zone but also the nose length. It all has to do with balance and the locations of the Center of Gravity and Center of Pressure. Some designs are easier to unsettle than others which then means there are designs that are more able to resist those unsettling forces. I would think a well designed bullet would be worth having.

Just how important ballistic coefficient of a given bullet is I don't know. You don't want a brick, but you can NOT shoot VLDs either. I think Bruce Molds (RIP) believed that nose drag was an important consideration in transonic shooting, but I don't know enough about any of that stuff to say anything.

I would like to know what a bullet design that offers good transonic qualities looks like. I think we have seen some more or less standardize designs that have preformed very well when the twist is correct and velocity is sufficient. One is the Lyman 410663. I also think the early money bullets were a good design before everyone rushed to make the nose more slender (lighter) and more pointed to claim a higher BC. There are some similarities between those two designs, the original money bullet and the Lyman Snover and the Metford for that matter.

I also think that Metford's design was and is a good one along with the original Sharp long range bullet which later became the original Ideal Postell. Where most shooter who have tried these and failed went wrong is in trying to shoot the 1 1/2" long bullets that were used in the 1870s in twists that are not fast enough to actually stabilize that length. That may work in dead calm winds or very light winds but turn up the winds a bit and they get really squirrelly. They most have had trouble in the wind with the slow twists of the 1870s as well.

Take either of those designs and get the length and twist right and they are good designs.

[Semtav]

think we have seen some more or less standardize designs that have preformed very well when the twist is correct and velocity is sufficient. One is the Lyman 410663.

I agree. That was my first sucessful bullet when I got into this game. Often wondered why it hasn't been duplicated in more moulds PP and 45 cal. Or maybe it has.

[Kurt]

I'm sure those of us looking for the best bullet for these rifles have a collection of different moulds that we collected over the years. I know I have.
And we all get caught up in the sleek looking bullet profiles that are used in the high power rifles, and in my opinion that is where they are better suited for. I know I tried them.
These slow moving projectiles we shoot mostly under 1400 fps they need a fast ROT to keep them stable. My .44's and I have several in this caliber with a ROT of 1/16, 1/17 and 1/19 and most of these sharp pointed long nosed bullets shoot well close in all of those twists I listed, but just because I see groups under a MOA at 200 yards they fall flat on their face in some of my calibers when the range gets farther out.
The bullet in my photo stuck in that .44-77 case stays stable out past 1500 yards in my 1/19 Rot .44-77 and the .44-90bn with a 19 twist as well as the faster twist straight walled calibers .44-75 Ballard and the couple .44-2.6 and I also use this profile in my .40 calibers.
No it's not the sleek pretty looking HP designed bullet but it works in all calibers I shoot them in.
Back in the 1870's they had the capability to make any bullet shape I'm sure, but they stuck with this type for some reason.

I think sometimes we don't spend enough time with a bullet to get the most from it finding a proper load for it.
Just because you have to give it an extra twist on the elevation knob compared to the sleek bullets don't mean they won't get the job done.

Kurt

[Distant Thunder]

I think if one were to put some thought into converting the 410663 into a .45 caliber pp bullet that would match the chamber dimensions and twist rate of one's rifle the rewards would be worth the effort. I'm sure Brooks could cut a mold and probably already has. In a 16-twist .40 that bullet really shines.

It did not work at all in my 18-twist .40-65. The first thing to establish is the length for your twist rate. Then the nose length and ogive radius and the tip radius. The diameters would depend on the chamber, brass, freebore and bore of a particular rifle of course. If I can find a little time in the next couple weeks I'll draw up a .45 caliber paper patch version of that bullet and see what it looks like. For an 18-twist of course. That would be interesting.

[Distant Thunder]

Kurt,

That's a purddy one!

[Don McDowell]

Brooks original postel nose in a 45

[Don McDowell]

BACO bullet copied from an original Ideal postel bullet.