Balck powder cartridges, long range, and the speed of sound

[Hickok]

Just curious, as I know that high power, long range shooting takes into account when a jacketed bullet will stay above or below the speed of sound/sound barrier of approximately 1100 fps, depending on altitude, humidity etc.

Does the sound barrier velocity/ about 1100 fps affect the big black powder cartridges as to accuracy as much as jacketed bullets?

Seems a lot of the long range "buffalo cartridges" used in the past and the BP cartridges used in the hitting steel targets at long range are starting out in the 1200-1400 fps muzzle velocity range. I realize these big 40-45 caliber boolits hold velocity quite well, but it would seem somewhere down range, they are going to drop below the Mach speed on their way to 1000 plus yards.

Do the big bore boolits get erratic or loose accuracy as do the jacketed bullets when dropping below the speed of sound?

[Don McDowell]

Sometimes they sure do, it largely depends on bullet length being balanced with the velocity and barrel twist.

[Gunlaker]

Most BPCR rounds will be below the speed of sound by 200 yards. There are combinations that will push it into the 300 yard range or so. Kenny Wasserberger's .45-110 will keep them supersonic at 300. You can tell when you are in the pits :-)

I'm sure that there are some problems that can occur, just like with smokeless rounds, but if you stick with standard bullet designs and twists it doesn't seem to be a big deal.

Chris.

[Lead pot]

Hickok I have a lot of different moulds with different bullet profiles in calibers from .40 to .50. Just about all are the paper patched.
When I was a kid I played with tops a lot, no TV's or computer games back then :) and the tops I liked the best were the fat short round tops compared to the tall slender tops because they would spin stable longer then the tall skinny tops. Well I still look at that with these bullets shot with black powder loads. Yes the nice long nosed bullets cut through the air better with maybe a few minutes of less elevation on the rear tang sight but that long slender nosed elliptical with a 3 or 4 caliber long radius gets a little squirrely when the winds kick up or the rotation is not fast enough (like the tops I mentioned) for this type of bullet. You can make both types of nose profiles work well when you learn what it takes to get the most from either. Both will do the job well but the blunter nosed I find are the most consistent. To many think they need the hyper velocity to reach out or put game down. This is not always the best.

[rfd]

... and the tops I liked the best were the fat short round tops compared to the tall slender tops because they would spin stable longer then the tall skinny tops. Well I still look at that with these bullets shot with black powder loads. ....

a poignantly functional observation!

[Don McDowell]

And there's no substitute for putting rounds down range at a match to figure out what does and doesn't work.

[Hickok]

Hickok I have a lot of different moulds with different bullet profiles in calibers from .40 to .50. Just about all are the paper patched.
When I was a kid I played with tops a lot, no TV's or computer games back then :) and the tops I liked the best were the fat short round tops compared to the tall slender tops because they would spin stable longer then the tall skinny tops. Well I still look at that with these bullets shot with black powder loads. Yes the nice long nosed bullets cut through the air better with maybe a few minutes of less elevation on the rear tang sight but that long slender nosed elliptical with a 3 or 4 caliber long radius gets a little squirrely when the winds kick up or the rotation is not fast enough (like the tops I mentioned) for this type of bullet. You can make both types of nose profiles work well when you learn what it takes to get the most from either. Both will do the job well but the blunter nosed I find are the most consistent. To many think they need the hyper velocity to reach out or put game down. This is not always the best.Ah, I can understand this quite nicely! Thanks Lead Pot!

[Knarley]

A guy can learn something new here every day. Thanks Lead Pot, never looked at it that way.

[BRUCE MOULDS]

kurt's description of the top is a good one.
it is the very basis of bullet stability.
however let's muddy the waters a little.
firstly, the speed of sound has less relevence than the transonic zone, which is mach 1.2 down to mach 0.8, or1320 down to 880 fps for a mach of 1100.
our bullets start in the transonic zone, and leave it, becoming subsonic , at a fair distance.
with the top, it just sits there, whereas the bullet is pushing through air which puts pressure on the nose.
this gives the bullet a centre of pressure.
the bullet also has a centre of mass, and the difference between these 2 centres is called the overturning moment.
the longer the moment is (like a longer lever), the more we have to spin the bullet to keep it stable.
the higher the drag function on the nose, the longer will be the overturning moment, as the centre of mass does not move, while the centre of pressure is more forward.
we can shorten the overturning moment by reducing nose drag.
in the transonic zone, the elliptical and money noses have the lowest drag - look at aircraft and missile noses used at these velocities.
in the transonic zone, drag is rapidly decreasing with velocity, going from highest to lowest in that bullet's flight.
this has the same effect as bumping the top while spinning.
it can induce a wobble, form which stability can be regained, or totally lost.
in the bullet, this is accompanied by more instability things like shockwaves being emitted.
the spitzer is the worst nose shap in this instance.
the faster the top is spun, the more it will lean away from verticle.
a bullet is the same, in that its axis will lean away from the trajectory to the right for a r.h.twist.
this is called the yaw of repose when all the forces on the bullet become stable.
it is also the reason why spinning a bullet too fast reduced b.c. the frontal area increases, taking drag with it.
the yaw of repose is also affected by forces from side winds, and gravity.
it will try to lean into a side wind.
when that wind suddenly changes (wind shear) forces on the bullet change, again like hitting the top.
as time of flight increases, contrary to urban myth, spin decays, and with it goes stability.
so we need to start the flight with enough spin such that the bullet still has enough at point of arrival.
keep safe,
bruce.

[Hickok]

Let me run this by you all, and correct me if I am wrong.

The short, fat, blunt/round nose, large caliber boolits are less affected as to "wobble" and instability as they pass through the 1300-800 fps transonic, subsonic zone than the long skinny pointed spitzer rifle bullets.

The big blunt boolits are more accurate and stable in the 1300-800 fps velocity domain than the sleek, long pointed rifle bullets which become wobbly and inaccurate in the mach speed area.

[Don McDowell]

There's to many other things that fall into the equation with these big hunks of flying lead to make a simple yes or no answer to your question. One of the problems that high-power shooters have adapting to bptr shooting is the fact that conditions that won't even make an SMK bullet flinch will make even the best of these bullets puke their guts out.
Barrel twist, bullet length, and wind conditions all fall into the equation with these bullets. If the bullet is at the top of the length for the twist and velocity even the slightest of crosswinds will send a bullet into instability when the distance gets long enough for the velocity to be dropping close to 1000 fps. If the bullet is just slightly under the "optimal" length it will hold up much better to 1000 yards.

[oldred]

Wow this has got to be one of the most informative threads I have ever read! That post referring to the tops cleared up something I have puzzled over several times and BM's post is a real gem! There is one line of that one however I am having bit of trouble wrapping my mind around, probably just the way I am reading it,

[it is also the reason why spinning a bullet too fast reduced b.c. the frontal area increases, taking drag with it]

Still this sure has given me something to think about, thanks guys this has been very enlightening!

[Lead pot]

Here are three bullets I use in my .40-65 with a 14 ROT. Last fall when I was working up loads for this new rifle I put a 4' square piece of R board in the fence at 862 lasered yards after the corn was picked with these three bullets. I don't know what the velocity was but the load was 60 grains of 1.5 F Swiss with two .040" plastic wads under the bullet. I would guess the velocity was maybe 1320 or so. I used a heavy cardboard on the 1/2" foil covered R board.
All three bullets have a different ogive lengths. The center bullet is a clone of a Medford that is 1.397" long, the left is a elliptical 1.397" long and the one on the right has a very long ogive and it is 1.398" long. The dimple you see on the two left bullets is where the shank meets the ogive. The right I did not have marked at the time of the photo but it is quite a bit longer then the far left. Shooting these three bullets with the same powder load cut all holes round but the far right 8 out of 10 had signs of yaw some holes had some very large oval cuts through the cardboard. but none key holed. The ogive shape does make a difference at long range. The right bullet to this day at 200 yards has cut the tightest groups over the other two but it will fail at long range from what I have seen so far. The center bullet had the tightest group with the left just a couple inches larger but conditions changed by the time I got to this bullet.

220124

[rfd]

kurt, are those bullet shanks parallel or tapered?

[Lead pot]

parallel Bob

[rfd]

thanx, kurt. just curious if anyone is shooting tapered ppb slicks.

[sharpsguy]

I have a couple of tapered molds, but settled on parallel sided bullets several years ago.

[rfd]

i guess that tapered bullets would help with chambering into a fouled barrel, something that ain't gonna happen with me.

[Lead pot]

I have three tapered bullets. One mould is a Tom Ballard .45 tapered that patches to groove at the base. One is a .44 Cal. swaged tapered and the other is a KAL. 44. All three will patch to groove depth and all three shoot well. I got them for shooting dirty with out fouling control. Just load and shoot. The two .44's are of the gibbs profile. The Ballard .45 has a long ogive with a 3/16 meplat.

[BRUCE MOULDS]

old red,
google "yaw of repose"
it will explain why drag increases due to increased frontal area as yow is increased due to faster twist.
this will possibly also explain spindrift, as it is yaw of repose that causes that.

kurt,
i have had bullets do a little wobble at 600 to 700 yds and then go back stable again at further distances.
it is not a good thing, but better than the bullet tumbling.
i just kept having moulds made shorter until the issue went away.
it is surprising that your pointy bullet exhibits wobble, but facts cannot be denied.

a really good example of bullet shape and stability is a comparison of the sierra matchkings 30 cal 168 and 190 gn.
in a twist adequate for the 190 (often used 1:11 or 1:10) the 168 will tumble prior to 1000 yds, while the 190 will remain stable out to extreme ranges.
the 168 should be more stable, but airflow over it is erratic.
keep safe,
bruce.

[BRUCE MOULDS]

hickok,
there are 2 types of bullet stability.
one is gyroscopic stability and the other is dynamic stability.
gyroscopic stablility, sg, can be calculated, with the number 1.0 being absolute min for stability, and 1.5 being the goal for smokeless supersonic bullets at normal ranges.
thgis stability is relevent to the spinning top.
dynamic stability is a different cat to skin.
even top ballisticians cannot fully understand it to this day.
it is accepted fact that you really have to fire a lot of shots to fully eastablish data on a specific bullet at different velocities and twists.
airflow and balance are some of the factors that come into play.
you cannot generalize.
keep safe,
bruce.

[BRUCE MOULDS]

there exists a skin of air on the surface of a bullet in flight called the boundary layer.
friction partly sticks this air to the bullet, and partly it is kept there by clinging to the point.
if the point is too sharp, the boundary layer will let go, and another one will form in ita place.
understandably, this repetitive action will disturb the bullet's stability.
the air flowing over the bullet is not doing so in a clean manner.
the original money bullet design called for a meplat (ball at the front of the ogive) of 50 to 55% if calibre.
the metford bullet meplat was this or a little more.
something to do with clean air flowing over the bullet.
the ellipse also seems to offer clean airflow.
transonic aircraft often exhibit one of these two profiles.
fuel economy is a great reason to look for reduced drag.
also there was loss of human life exploring trans and supersonic flight.
to go super you have to go through trans, and come back through it to land safely.
a major contributor to increasing b.c. is to lengthen the ogive.
this is easy with jacketed bullets, because the jacket supports the nose.
our black powder bullets have unsupported noses, allowing the nose to set back on firing, thus reducing apparrent b.c.
if they do not do it the same each time, each bullet will have a different b.c., putting more vert in the group.
even worse is that the setback can bend the nose moving the centre of mass away from the axis of the bullet.
when this happens, spinning the bullet faster diminishes stability rather than improving it.
harder alloys help here.
my own take on this is to not have a nose as cast more than 1.5 calibres in length, and use an alloy 16:1 to 12:1.
others differ on this and get good results.
the ellipse is defined by a formula using 2 axes so the shape is easy to define, and the money/metford is easy to define using meplat diameter, ogive radius, and nose length.
a pp bullet will have a cleaner airflw than a gg, simply because it has smooth sides.
keep safe,
bruce.

[Hickok]

Really great information, thanks guys!