Let's talk TRANSONIC!

[Rick Mulhern]

Oft times we read articles whereby the author of whatever talks about a particular bullet or cartridge not being accurate because it can't remain supersonic throughout the distance to the target as it goes into the transonic stage...the bullet gets 'squirrelly' and accuracy suffers! One example of this is in years past when working the pits we could always tell who the Service Rifle shooters were when shooting 1000 yards because oft times the 168 gr. Sierra bullet being used would keyhole into the target paper! That bullet was NEVER designed as a long range bullet in the first place, however it set world records over many years in 300 meter matches! It had a 13 degree boat-tail and any bullet with that design has the same drag function as a flat-based bullet.

Now...here's some food for thought! The below photo is of a metal Creedmoor Target I had made a few years ago when I was heavy into shooting Sharps rifles using paper patched all lead bullets that I cast. There is a smaller plate inside the larger. Small plate is 20" diameter...larger bull is 44" diameter...same size as the Palma target. Ten ring is the 20" plate. I had this target made because when shooting from 1000 yards the bullet impacts stood out like a five carat diamond in a Billy goats ass in my spotting scope. I was testing a new load in my 50/90 Sharps using a 720 gr. paper patch bullet ahead of 116 grs. KIK 2F blackpowder using Russian primers. I wanted to see how the load held up for possibly giving a low vertical dispersion. Muzzle velocity of this load was around 1380 fps so it shouldn't take a rocket scientist to figure that this bullet was already below super-sonic at around 250 yards...or less! After a first round hit on the ten ring plate I made no adjustment for windage correction as the conditions were good with only slight wind and since I was testing for vertical....not a problem! Had I made a correction probably all ten rounds would have been within the ten ring plate. A measurement showed a 7.5" total vertical for all ten rounds!

So....in the final analysis...the question is why was the accuracy this good using a 125 year old bullet design using an out-dated propellent, moving at this below supersonic speed??? Another question is.....is all the talk about 'going into the transonic stage causing inaccuracy' just so much BS??

1000 yards 50/90 PP by Sharps Man, on Flickr

[Don McDowell]

Rick, I'm thinking that rather than the bullet going "thru the transonic range" it's more a matter of the bullet reducing velocity to the point that it no longer remains stable due to it's length, the twist in the barrel and muzzle velocity combined.

[Rick Mulhern]

I was wondering if anyone was going to bring that up!!

[Don McDowell]

I think one of the most interesting things to ponder on this is the 223/5.56. If you look at how far things have progressed with that cartridge and twists, it makes for a pretty good source of information.
The original 12 and 14 twist wouldn't stabilize a bullet heavier than 55 grains, but as they have increased the rifling twist, that cartridge now will rival the 6mm's at distance.
The problem we have with these big ol chunks of lead, and blackpowder is the lack of velocity to take full advantage of faster twists and heavier bullets.

[Distant Thunder]

Because the transonic range is generally said to be from 1350 fps to 900 fps ( Mach 1.2 to 0.8) and that also just happens to be the velocity our long range BPCR bullets send most of their time it seem that a bullet designed to remain stable in that range would serve the shooter best. That may not be the sleekest, highest "BC" bullet. I don't believe it is. I believe it starts with a bullet that does not push the envelop of what length is stable for given twist, but rather a bullet length that is well stabilized by the twist rate of a given rifle.

What nose shape is best I'm not 100% sure, but I believe I am at least headed in the right direction with my current .45 caliber paper patch bullet. I wish I had more time to experiment with nose shape. I have no doubt it needs to be a smooth sided paper patch bullet with a flat base.

It has been a fun and rewarding process.

[Kurt]

The length of ogive radius compared to the shank length makes a lot of difference even when the bullet length is comparable to the ROT.
The shorter the ogive radius length the most stability you will have even if the bullet is longer than the regimented length for the ROT.

[Distant Thunder]

I'll be the first to say I am not any kind of an expert on this subject. Everything I say is just based on my own experience and the development work I've done over the past 10 years with paper patch bullets for long range matches. What I have been using is just something I stumbled into by applying things I've read about projectiles in the transonic range and what is supposed to work best.

I am fortunate in that I have a few machines and that has allowed me to make my own bullet molds, some of which actually work.

The bullet design that has worked best for me over the past 10 years and the one I keep returning to is an elliptical profile that is capped with a approximately 30% of caliber radius. The overall length is 1.440", which has worked very well in my 18-twist .45 caliber rifles. The nose is .765" long leaving the shank at .675".

I pretty sure every long range match I have won with the exception of two, in which I shot grease groove bullets before switching to paper patch, was with this one design. Other designs I tried shot well for me, but I can't remember winning a match with any them. This one works!

So I don't know that it is THE bullet design for transonic shooting, but it's a darn good one.

[Kurt]

Man I belong to the mould and swage die club of the year. I been looking for that magic bullet that will resume it's sign of sight after it went into a warble and get back on corse and hit true to aim. I duplicated the Lapua rebated BT for the .40/70 and .40/65 and Ellipticals and a variety fo other profiles and I made all shoot well enough to splinter bowling pins at 200 yards and cut some very tight groups but when the conditions get rough at extended ranges like I shoot out in Montana I reach for the original Sharps or Gibbs bullets or a profile like the postel.
Well since I got the new .40/65 I'm back at it again with the long slender nosed bullets but before I get done I will have another .40 caliber mould made with the original Sharps that is in the .44/77 in the picture. I had a .40 mould but I forgot who I loaned it to. I got tired sending bullets so I just sent the mold
           

[Distant Thunder]

Kurt,

There are certainly no flies on that .44 bullet in your 1st picture. That is pretty much the design I tried to replicate when I made my .40 caliber bullet, I call it my ODG bullet. It is quit possibly my most accurate PPB at 200 yards and has done well out to 600. I can't play with those long sleek bullets in that rifle because of the 18-twist, not that I'd want to anyway.

   

My .45 caliber bullets isn't really pointy even though it has a fairly long ogive. I have duplicated that nose in the 2-diameter bullet for my old .45-70. I figured I would start with that nose because I can always recut it to the ODG nose if it doesn't work out. That mold has been sitting there for a few months now just waiting to be finished up and tested. To many other things keep getting in the way.

   
This is the .45 caliber bullet that has won several long range matches for me. It is the bullet I shot that 98-4X with at the CUP match last year, in the end I finished second by something like 6 points. I won the Long Range Championship and the Long Range Fall Classic with it last year too. And the Fall Classic the year before. Performance like that is why I have come to believe it is a good design.

Now we are having one winter storm after another and that brings the usual break downs that I have to fix, the snow blower and my plow. I just got the snow cleaned up today from last night and I have little time to do repairs before the next storm hits later tonight. I'm not sure which is worse, 20 below or 18 inches of snow! I guess it come down to whichever one you're dealing with at the moment.

The bad part of all the snow is that it's making it really hard to get around in he woods so I can cut firewood. I'll probably just end up cutting what I can and waiting until the snow is gone in the spring to haul the wood. That worked out so well for me last winter, half that wood is still laying in the woods under two feet of snow! You might say I'm a bit behind. I can only hope we have an early spring!

I should probably make one more mold for my Hepburn, one like your .44 bullet and the run it head to head with my elliptical and see which one comes out on top. I think I know the answer, but it would be fun to test.

I will say that I have found that old design much easier to get good accuracy with, they just seem very forgiving.

[Kurt]

Jim I always said that the old dead guys had this all worked out in a lot shorter time frame since they changed from the patched round ball front stuffers to the cartridge suppository loaders.

Rick as far as your topic passing through the subsonic zone I think it has an effect on the stability, how far down range it goes before it works way out the yaw it travels or if it ever does I have no idea. I have put a lot of pasters over holes when pulling targets at long range that are egg shaped and looking at the shooters bullets he sent down range are mostly the long nosed bullets.
I don't know what goes on in this zone but I remember reading when pilots first tried to break the sound barrier with their P-5's putting then into a nose dive and a lot of then crashed when they tried to pull out of the dive till one figured out that the controls were reversed. I don't remember his name.