Transonic Stability, velocity, and profile?

[curioushooter]

Been messing around with heavy 44 Special loads with three different bullets: Lyman 429215 solid (220 grains), 429244 HP (240 grains), and the H&G 503 solid (262 grains). I use the same alloy in all: 96-2-2. The lighter pair of bullets being propelled by 8.5 grains of Unique and the H&G by 8.0 grains of Unique (though I am thinking of maybe moving this up to 8.5 as well). All in starline brass with CCI 200 primers and carnuba blue. Sized .431.

The velocities out of a 5.5" Ruger Blackhawk are 1100 FPS +/- 15 FPS for the 429215, 1150 FPS +/- 10 FPS for the 429244 HP, and the 503 comes it at 1015 FPS +/- 3 FPS. All six shot strings. Accuracy is fine at 25 yards and they barrel stays clean.

I've been taking these out to 50 yards and even trying my hand at greater distances and I am finding that the accuracy of the 429215 sort of falls apart. The the more sluggish 503 on the other hand seems to do better with the 429244 in the middle (I get flyers on this one that I think are due to voids in the casting due to the HP pin). I feel like I was doing better with the lighter bullet in the summer. Could this be due to transonic destablization? Something I learned years ago about 38 wadcutters is their accuracy goes away if you push them hard and they can wander. Something that you can put a whole cylinder through a dime sized hole at 15 yards just totally falls apart at 50. Could it be semi-wadcutters do the same thing?

Anyone have observations relating to velocity, nose profile, twist rate, temperature (speed of sound), that should be in order for solid performance at moderately long handgun ranges like 75 yards? I've been trying to settle on one load to rule them all. Perhaps an impossible thing, but I am trying to get solid 75 yard accuracy, not-unpleasant recoil, and adequate effectiveness on deer.

[Harter66]

I had some great loads in a 45 Colts carbine with the 454424 . I was shooting 50 yd 5" post leaning groups with them in a 7.5" RBH and 16" plates at 100 wouldn't have been really hard . The carbine had half the twist and 190 fps faster speeds , 1240 fps . 25 yd 10 under a half dollar . 50 yd a silver dollar would still touch 10 shots as long as I did my part . At 75 yd 1/3 were at least contact on a Golf ball and a softball would have not lasted very long . Someplace between 78-82 yd the bullet would depart the line of flight at about 10:00 and at such an angle as to miss a berm under 7' in hight . The Strelok app says 1100 fps at 75 yd and 1080 at 80 yd and 1040 at 85 from a 1240 fps start .
That was at 5500 feet MSL the load really tell apart at near sea level Goliad Tx 12+" inch 50 yd groups , switch to a 1050 fps MV load that only clocked 850 in the RBH and 100 groups were a real thing .

This has been argued to death but my conclusion is that the transonic speeds caused the bullet to tumble in the 1-32" where the 1-16" was able to hold on to stability and while groups suffered they were still groups .
Start fast enough to stay super or start sub and heavy .

[Castaway]

The day I was working up a load for the 6 lbs of BR 5 powder I just bought. One load produced a sub MOA group at 50 yards. Man, I thought I was on to something and went to 100 yards. Same everything; bullet, primers, brass and weather. The sub MOA load went to 10”. Plugging in data to in ballistics program indicated the bullet transitioned between 60 and 70 yards.

[waksupi]

At your velocity, you are not going transonic. Some other gremlin is at work.

[dtknowles]

At your velocity, you are not going transonic. Some other gremlin is at work.

The speed of sound at 40 deg. F is 1096 fps and at 80 deg. F is 1138 fps. He said his velocities are in the 1000 to 1160 fps range. Some of his shots might start supersonic and could drop below the speed of sound before they hit the target.

Tim

[charlie b]

Transonic is Mach .8 to 1.2

It can do funny things, but, many people have had success with SWC designs that transition during flight.

[curioushooter]

Start fast enough to stay super or start sub and heavy.

That's what I was thinking, but it makes me wonder why Keith liked the the SWC at 1200 FPS. Surely he would have figured out that it's long range accuracy fell apart if it did?

[Mal Paso]

Start fast enough to stay super or start sub and heavy.

That's what I was thinking, but it makes me wonder why Keith liked the the SWC at 1200 FPS. Surely he would have figured out that it's long range accuracy fell apart if it did?

Keith's load behind a #503 will do 1500+ fps from a 6 inch barrel revolver. One warm batch of 2400 went 1604 fps.

[Goofy]

As suggested above, the transonic realm runs .8-1.2 Mach and it is where the highest drag on a bullet occurs. Drag as in aerodynamic pitching moments versus center of gravity and gyroscopic stability factor. Most don't look at it any deeper than to compare bullet velocity to whatever SoS they calculate based on atmospheric conditions. It is a very misleading approach. What matters is the velocity of air in the flow field around the bullet. It is a higher number than bullet velocity.

273499

[gwpercle]

Load up some heavy Elmer Keith loads with 2400 for long range work .
Might want to read his books "Sixguns" and "Sixgun Cartridges & Loads" he was into long range shooting with the 44 magnum and 44 special . Brought down a wounded deer at 400 yards with a 44 magnum S&W . No sense re - inventing that wheel ... Also both books are interesting reads !
Gary

[beagle]

I'm gonna weigh in here and probably don't know what I'm talking about but here goes. Felix and I did a lot of work with the .44 Magnum a couple of years before he passed. He was a pretty savvy ballistician due to his bench rest days. He said there was definitely a transonic shift on bullets. This was manifested more often in pistol rounds that in rifle round as rifle rounds took longer to go subsonic and weren't affected at the ranges used than pistol round did.
I've seen the 429215 and the 429421 discussed above. I had a 429215 that would punch one hole groups at 50 yards but go all over the place at 100 yards. Something was evidently happening there. The 429215 is a short stubby little squirt and I felt that it was "going to sleep" faster than the 429421. The 215 on the other hand lost velocity quicker as it had a lower sectional density and the transonic transition occurred at a critical time in it's flight and was affected at 100 yards. The 421 was still "going to sleep" at about 100 yards, the transonic shift not affecting it as much as it was still stabilizing.
Now. I don't know what all this means but I know something happens to some bullets and don't to others at transonic shift. It may be in the design and aerodynamics and it may be something else. Felix said you could see it on paper but I never set up multiple targets to check his theory out and he did./beagle

[charlie b]

If you watch a shape go through transition you will see various things happen.

Approaching Mach 1 you will see the front shock wave start to form, a curved shape in front of the bullet. Then the shock wave gets closer to the nose and sometimes smaller shock waves will start to appear at various parts of a bullet, especially one like a SWC. These are where the local velocity is exceeding the speed of sound before other locations on the surface of the bullet. This is where the instability can occur. As the velocity increases those shock waves will 'move'. Increased more and the major shock waves will 'attach' at the nose and tail.

Basically the air pressure points on the bullet are moving, which changes the stability factors.

Now consider all that happening in reverse as a bullet slows in flight.

[Goofy]

273544

[44magLeo]

I think part of the reason the 503 shoot better at longer ranges is B/C The longer heavier bullet has a igher B/C than the lighter shorter bullet.
At the transonic range the high B/C bullet is less effected than the low B/C bullet.
I tend to like bullets in the heavier weights. 245 to 265 grs, not the extreme heavies like the 300+ grs.
I shot the 429421 for a long time out of my RSBH and Marlin 1894. Recently I got The NOE version of the RD 265 gr RFN boolit for the Marlin. I have not shot it much yet so I can't comment on it much but to say it seems to shoot well.
The 44 special cases I did load with the 429421 I used 7.5 grs of Unique. It shot well.
Compared to my heavy load in Mag cases of 20.5 grs 2400 under the same boolit both shot very simular groups at 50 yards. Less than 2 inches.
What I found unusual was that the light load hit a right on at 100 yards and the heavy load was right on at 50.
This let me shot both very well without having to adjust the sights.
With the either load a woodchuck was in real dager out to around 125 yards. Get out 150 plus They ha about a 50/50 chance.
On a deer sized target 250 yards was not a hard shot to make. I never tried one that long but could keep all six shots on a gallon jug at that range.
The farthest I shot at a deer was 125 yards. Bang flop.
I did a lot of practicing at the longer ranges just to see if it could be done. I did well enough that I believed Elmer Kieth could have hit deer at the ranges he cliamed. He was a much better shooter than I. Adfter all he lived with a handgun most of his life and shot them a lot.
In your Special I would use the 503 bullet and try a some 2400 with it.
You might find it reaches the velocity you want with ,lowe pressures and maybe better accuracy.
Leo

[PAndy]

Sierra shows ballistic coefficient over a range of velocities, at least for rifle bullets. I have noticed that the round nose bullets (such as a 30 cal 180 RN) have a much higher BC at slow speeds compared to the BC at 2000+ fps. The longer tapered bullets (such as a 180 match king) have a similar BC across all speeds. Yes these are jacketed not cast. So there is a lot going on with different shapes. We shot 500 grain cast and black powder out to 500m with 45-70s years ago...many folks still do. These went from supersonic to subsonic, yet we had very good accuracy. Long round nosed bullets. The experienced guys all said the heavy bullets were necessary for that game.

[OS OK]

Love these kind of discussions!

[dtknowles]

The lowest drag shape for subsonic bullets would be a round nose boattailed bullet with a length 3 times the diameter and made of pure lead or denser material. For super sonic longer and pointier is better. Short fat bullets are going to want to go sideways at any speed.

Tim