Ballistic Coefficient vs. Accuracy?

[Distant Thunder]

Kurt,

My experience with money bullets is the same. Dan designed a bullet for my .44-100 Remington straight that I had at one time and of course it was a money design. Looking back at that bullet now I believe the only thing he got right was the length! I put a lot of time, powder and lead into trying to get that bullet to shoot and it NEVER did any good beyond 100 yards!

It would put 10 shots in less than an inch at 100 yards and i couldn't keep 5 shots on an 8 1/2 x 11 inch piece of paper at 220 yards, or sometimes, just barely.

The bullet Dan drew up for me had a long, slender, very pointed nose and to me at the time looked like it should shoot very well. I just didn't understand the transonic zone at the time, but now I do at least a little.

I've gone back and traced to "evolution" of Dan's money bullet. It started out as nothing more than the Metford bullet design when he started working with it. Then he tried to up the BC by shaving down the nose and making it longer. I believe that was a process that continued through at least a few steps and molds. Then the money design had some early success and everybody wanted one the mold makers began to turn out their versions of "THE MONEY BULLET". I think there was some attempts to almost compete for the pointiest Money bullet.

The crowd that builds a new rifle every year chasing the next new best bullet design, caliber or twist rate did as you say, they started to spin this design faster to get more Static stability and keep it from yawing excessively. So we moved to 16-twist .45s and now there is talk of trying 15-twist! All this is an effort shoot through the transonic zone with accuracy.

So we have two schools of thought just like the long-range precision shooters, those who try to spin their way through the transonic zone and those who try to do shoot through it by using bullet designs that opt for greater dynamic stability and just enough static stability to travel through and emerge still on course. You and I are in this second group and your experience and that boat anchor made of molds helps strengthen my thinking while paralleling my own limited experience. And that of other shooters I talk to.

While I favor the bullet design approach, as you do too, I do believe that both can work. You can probably, maybe even obviously, drive a very high BC bullet fast enough and spin it at a very high rpm and have success. The thing I was trying to make clear in my pervious post was that when you spin a bullet TOO fast you can lose dynamic stability and have your bullet NOT track on the trajectory path. When that happens it could fail under some conditions. That is the problem with pushing to the extremes, it can work, just not all the time.

[Kurt]

I feel it's the length ratio between the elliptical ogive and the shank that throws the balance out the window and not so much as the diameter of the nose hemi. Keeping the elliptical radius short you can get away with it.

I could see Dan with his HP match shooting background trying to change the black powder bullet profiles close to the HP bullets and this is where his MB designs started.

Brents prolate bullet has the ogive similar to a football and he does well with it. I have one of his prolate moulds I got from him and it was on the long side and I ended up shortening it twice and it does well but it falls short at extended range at the gong shoots where high winds are common so I retired it.
personally I think if he would have stayed with the bullet he used on his web site and did away with the cup base and shortened it to 1.400 or 1.425" it would have been a better choice for the .45 cal 18 ROT. That bullet was more inline to the old long range bullets.
I personally like a bullet with a Tangent ogive radius length of around 2.4" over the longer elliptical and a ball hemi of .26", maybe a smidge larger.
This swaged bullet I use a lot and I swage it with a cup or flat base.
It's a copy I had Rich Corbin make of a Metford.
Hey there is no end if one really has an interest in the old shooting ways. I started in the early 50's looking for a better way but I end up back where I started. It worked good for the ODG's and it still does for me.

Kurt

[Distant Thunder]

It is a common mistake to try and apply high power principles to BPTR and it totally ignores the fact that like it or not, accept it or not, we are in the transonic zone for around 80% of the bullets flight. The rare exception is the guy with 100 grains of powder in his cases and even then, his bullets are in the transonic zone by 200 yards, not subsonic, but transonic. I don't think everybody understands the difference.

Subsonic is below the speed of sound which is roughly 1130 fps depend on several conditions. Transonic is the zone where the sonic wave produced by the bullet has an effect on the bullet, 1346 fps to 897 fps. In that velocity range the bullet is being influenced by the sound wave that is initially produced in front of the bullet then as the bullet slows down the sonic wave moves first onto the nose of the bullet and then moves toward the base as the bullet slows even more to the 897 fps mark when the influence stops.

This sonic wave cause all sorts of stability and control issues and is why aircraft don't fly in that speed zone. Bad things happen!

[Don McDowell]

Late to the party, but if given the choice, I would first test the bullet on the right, and then see how the bullet on the left compared.
Personally I don't think the "transonic" zone is as much trouble as some would make it out to be. I'm fairly well convinced most of the problems occur in long range matches due to wind currents above the flags where the bullet is traveling and beginning the apex when shooting at distance. We simply can't see what's going on above the flags, except at Raton it is sometimes helpful when spotting to look at the mirage against the mountain in the back ground well above the target butts.
It was interesting in the pits at Phoenix this year, even at 1000 yards when the winds were full value tail winds the muzzle report and the bullet would arrive at the same time. Wind switch a bit to one side or the other and the bullet got there first.
Also note that pulling targets for someone shooting a 2 7/8 target at 200 and 300 yards ear plugs are still a handy thing to have.

[Distant Thunder]

Yea, a 2 7/8 pushed hard can still be supersonic out to almost 400 yards, if 1500 fps at the muzzle, but it better be a heavy rifle! I don't think I'm man enough to shoot something that through an entire match.

I think it helps to have a bullet designed to deal with the transonic zone, which we can do. We can't do anything about what happens above the flags but hope.

I had mirage running in two different directions at Raton, one way at the top of the targets and the other way at the bottom. And there was a 3rd mirage on the targets. I was a bit overwhelmed.

I've seen some weird shit in the mirage at Lodi too. Every once in a while, I look in my scope and say WTF is that! Ain't it fun.

[Kurt]

Shoot the big hill at Baker Mt sometime. You will see the flag pointing up to the sky.

[Don McDowell]

Jim at one of the matches in Phoenix this year, the flags and the mirage looked like you needed about 3 right, but in real world it took 2 left. And then it switched. LOL

[Distant Thunder]

I like it at Lodi when the flags on the left are straight out to the right and the flags on the right are straight out to the left. ?

[Don McDowell]

Flags often don't tell the real story. LOL

[Kurt]

I like it at Lodi when the flags on the left are straight out to the right and the flags on the right are straight out to the left. ?

Seen that a couple times. And the pit flags just about limp.

At Alma Mich I think are the most strange conditions that I have yet to figure out. I find it best to look at what the tree tops are doing