[Oldnamvet]

Has anyone seen any scientific studies of the relative rates of loss of velocity due to air resistance of various shot sizes, initial velocities, etc?

[boilingleadbath]

Well, I'm not an aerodynamicist, as much as I like to pretend I am, but...
I expect that, once the pellets spread out 7" (or maybe less - this is really a guess), one could model the shot cloud as it's individual pieces without loosing enough accuracy to be noticeable. Up until that point, I would expect the velocity to decline slower due to the pellets being closer together.

...but because that effect stops being important so quickly, I don't feel it's important.

That said, we can calculate the Ballistic Coefficient of the projectile without much bother: ChairGun (an airgun ballistics program) lists the Bc and Cd of .177cal round (lead) balls. We find that the Cd of them is roughly what we'd expect from a sphere in the turbulent airflow regime, IIRC - .46. This suggests to me that we can extrapolate the Bc accurately. (ok, maybe not; shotgun loads are transonic, which messes everything up. Ignore this for now.)
The Bc is .014, their diameter is .18", and they weigh 7.8 grains.

Now, we find that there are 350 lead pellets of size 7.5 in an ounce, meaning that they weigh 1.25 grains. They are .1"
Now, knowing that the Bc = M/(Cd*A)... we put in the reletive values:
.014(Bc) = .16/(1*.31)
Solve and get a Bc of .00726

We proceed to take this Bc and a velocity of 1300 fps (pulled from thin air) and plug it into chairgun... ok, we don't plug 1300 fps into chairgun. It doesn't want to go that high... so we enter 1100. Sorry about that.
Anyways, onwards...

We find that it loses energy quickly... by 65 yards, it only has 10% or so remaining.

Now, I didn't bother to simplify the equations because I don't mind ugly equations, but here is an easy way to find the Bc of your lead projectile:
.078*(Diameter in inches)

I don't mind explaining stuff, if you want to ask about anything.

[45crittergitter]

I don't have the original source reference I got this from:

LEAD SHOT: The equivalent G1 ballistic coefficient for lead shot is approximately equal to 1/10 of the pellet diameter in inches. BC for the first 5 to 10 yards or so (down to about 1200 fps) is about twice that figure.

[suemarkp]

I collected some data from some publication a while back for retained velocity of shot. This is what I have and it is rather limited in size and distance:

#4 lead MV:1423 20yds:1006 30yds:876 40yds:773 50yds:689 60yds:618
#4 Tung-Fe MV:1466 20yds:1008 30yds:869 40yds:762 50yds:674 60yds:601
#4 HeviShot MV:1386 20yds:996 30yds:872 40yds:773 50yds:692 60yds:623
#4 steel MV:1422 20yds:896 30yds:752 40yds:642 50yds:554 60yds:481
#4 steel MV:1666 20yds:999 30yds:826 40yds:699 50yds:600 60yds:520
#2 steel MV:1653 20yds:1052 30yds:884 40yds:759 50yds:661 60yds:581

[Shell Shucker]

WOW! Quiet a large velocity drop in a short distance. I guess that explains how the cows could stand 100 yards from the skeet field and never even flinch! Any data on target sized shot?

[suemarkp]

I have this from the Canadian Police Research Center in a 1995 test, but I can't tell if the velocities were measured or calculated. Pellets are lead.

size 7½: MV 1220, 15m 865, 30m 675, 50m 500 (velocities in ft/sec)

I always had heard that 100 yds was considered the min safe distance for a skeet range, but that is only if the shot is fired upwards and in skeet sizes (8's or 9's).

[kirbythegunsmith]

Does this look helpful?

kirbythegunsmith@hotmail.com

http://i186.photobucket.com/albums/x109/kirbythegunsmith/vel-7-1.jpg

Matunas' book on ammunition is a very helpful reference.