smoothbore accuracy

[TRX]

Six or seven years ago I saw some commentary on a gunsmithing list from a smith who said he did a few smoothbore conversions to popular bolt-action rifles every year, since his area had a smoothbore hunting season. As I remember, he said accuracy was acceptable at 100 yards.

Later, I came across some information on modern tank cannon and field pieces. They've mostly gone to "penetrator" style rounds with high aspect ratio. As the bullet gets longer, it becomes impractical to spin it fast enough to stabilize it, so they don't bother with rifling. The projectiles are only stabilized by their shape.

Just recently I was looking at the .300 Whisper cartridge. It uses a very long bullet. So do a few others, like the old 8mm Mannlicher.

My google-fu doesn't turn up much other than old muskets and tank guns, but it looks like a smoothbore gun might not be a total loss if the bullet was right.

Has anyone come across anything about this, or done any experimenting?

[longbow]

If the bullet is right smoothbores can be accurate but that requires either a round ball which can give decent accuracy from smoothbore to 75 yards or so, or a drag stabilized projectile.

Long slender bullets of standard design require very fast rifling twists to stabilize and will tumble if if shot from smoothbores.

If you look up modern smoothbore artillery you will find that the projectiles are dart shaped and fin stabilized.

If you haven't seen it here is an article from Wikipedia:

http://en.wikipedia.org/wiki/Smoothbore

[waksupi]

I only know flint smooth bores, so can't say much about the others. Aside from the fact the guy making smooth bores from rifles most likely committed a federal law violation in each case.

[Multigunner]

There was a French shotgun slug design that used a bullet with eggshaped front section conected by a short shaft to a thick flat disc base.
If the projectile tilted in flight air resistence on the edge of the base most exposed to the slipsteam pushed it back into line of flight.

[Cactus Farmer]

I only know flint smooth bores, so can't say much about the others. Aside from the fact the guy making smooth bores from rifles most likely committed a federal law violation in each case.

??? I took a .219 shiney smooth hole in a 3/4 bar of steel and build a smooth bore 22. Not unlike the smooth bores they used to make for "rat shot" ammo. These origional guns are pricey today and I wanted to play with the "rat shot in a non rifled tube. Threaded it to fit an old Remington Model 12 pump. It patterns very well,much tighter than a rifled bore. It will kill birds at 10-12 yards well and is death on snakes. No sights with a small brass bead. I get some funny looks with it and would hunt dove but can't/won't bother to install a 3 shot plug. We have a really anal game warden around here and I don't want to give him a reason to mess with me.
It this toy illegal?Are the old "Moskeet" guns with the "Routledge" counterbored muzzles verboted too?Grandfathered in?
I thought if it is at least 18 inches long a smooth tube was OK. Less than 18 is where the problems occure.

[Multigunner]

Boring a Revolver barrel smooth bore to turn it into a shot pistol is illegal. Shotguns with barrels under 18 inches are prohibited without special licenses.

The Thompson Center shot pistols have rifled barrels in .45 caliber which allow use of pistol cartridges, and use a choke when firing .410 which straightens out the shot column and counteracts rifling induced spin.

I've heard that Westerners who want a peacemaker styled shot pistol for rattle snakes liked to buy up old pistols with the rifling worn to a mere trace from corrosion and rough cleaning, there not being enough rifling left to disrupt the shot column.

In Flintlock days it was common for guns to be constructed like a Pennsylvania Rifle yet have a smooth bore of large caliber, to double as a fowling piece while still useful for bush bucking with round ball. When used with bore diameter ball they often loaded these with two or more balls for extra shock effect on deer sized game at close range.
Many old rifles were bored out smooth as well.
Most of those originally made as smoothbores have the breech octagon for 1./3 to 1/2 its length then round to the muzzle, for better wing shooting when hunting birds with small shot.
I've heard that some even liked to fire short crossbow type wooden bolts from these smoothbores when they ran short of lead. Also smooth round stones from a creek bottom wrapped in greased leather would serve if no bullets were available.

A common trick used to obtain better accuracy from the Smoothbored Buck and Ball guns was to drill a hole in a ball and run a short length of stout cord through it.
When fired the cord trailing behind the bullet acted like a sea anchor on a life boat, keeping the bullet pointed in the same direction as when it first left the bore.

Marlin once marketed a smoothbore lever action that could fire a .44 shot cartridge or a .44 round ball.
Some 9mm and .32 Shot pistols and garden guns could also fire a very low powered round ball cartridge or the same caliber for shooting large rats or other vermin too tough for the light shot charges.

[Harter66]

Marlin recently marketed a Garden Gun , a smooth bore 22 intended for shot shells .

Seems odd to me that under the above info as a guide that 1 can buy a smooth bore ML pistol. Apples and oranges I know. Are the Ishpore converted to .410 smooth bores ? What about as an unlikely but possible situation of having a 12ga with a special marked slug action and a new smooth bore fixed choke bbl. Seems like the same thing as boring a rifle smooth.

[Multigunner]

Seems odd to me that under the above info as a guide that 1 can buy a smooth bore ML pistol.
Muzzle Loaders are exempt from practically all the rules that affect cartridge guns.

As far as I know theres no rule against converting a rifled long arm to smoothbore.
Besides the Enfield .410 shotties the Germans also converted many WW1 GEW98 actions to handle shot shells.

[TRX]

Maybe I provided too much information.

Has anyone here shot anything besides round balls in a smoothbore, and how did it work out?

[Dutchman]

A nearly worthless anecdote of the Revolutionary War days pertaining to round ball musket accuracy:

one went high
one went low
where in the hell
did the other
one go?


Dutch

[longbow]

I'll try again.

While I have not shot an elongated bullet out of a smoothbore "rifle" I have shot lots of elongated "boolits" of various sorts out of a smoothbore shotgun with rifle sights ~ so a big bore smoothbore. Even drag stabilized slugs tend to provide mediocre accuracy at best past about 50 yards. Many leave oval holes in the target paper in my experience which means they are not flying well.

If you take a look at pretty much any modern smoothbore artillery piece the projectile it is firing is fin stabilized.

Without some sort of fin/drag stabilization an elongated boolit will tumble if it is not spin stabilized. The longer the projectile, the faster the spin required to stabilize it.

Longbow

[Multigunner]

Well I can add that the same Bernoulle effect that gives airsoft BBs with backspin extended range works against the round ball as fired from a musket.
Musket balls were generally loaded bare over a paper wadding left from the paper cartridge when loading. Bare round balls picked up a rolling motion as they were pushed down the bore, a low pressure area formed under the ball pulling it down and reducing range, the roll was seldom equal in rpm so as Dutch said

one went high
one went low
where in the hell
did the other
one go?


So first step in getting any accuracy, or at least reducing its rainbow trajectory, is to tightly patch the round ball to hopefully prevent it picking up a rolling spin.

PS
I just remembered I have PDFs of several 18th and early 20th century books that have sections on the smoothbore and round ball.
I'll dig through these and post links to download those with the most useful information.

[Greg5278]

Try searching for the PMDK projectile. It was designed to be drag stabilized in a shotgun. You could scale it down to the desired caliber. The M1 Abrams tank gun is smoothbore, and accurate to almost a mile. You will have to check for other drag stabilized projectiles or Foster type clugs.
Greg