Creating spin / twist in a lead bullet out of a smoothbore

[kody]

  I have been trying to buy slugs for a 28 ga.  No luck except for a BPI round that uses a .505" roundball.  Pretty good, but I want more weight therefore having to go with elongation of the projectile. I've heard that with the original finned slugs the fins were missed by the air molecules because of the nose deflection. Brenneke slugs have the rotational fins set forward of the parallel siding of the slug and therefore catch the deflected air resulting in the best rotation of any of the slugs. I want to create spin by notching the forward rounded face of the lead bullet so that there is a rotational force imparted to the bullet. How many notches ,how deep, what degree of twist,raised edges to grab more air, notches clear to the tip of the nose and how to create these grooves; those are problems that I need help with. There are a lot of guys that have expressed interest in making something more of the 28 and saboted .54 cal lead bullets might be altered to fill the bill. Sound off!      Ken

[talon]

Some comments: The rear fins on some slugs may not have helped rotation, but they prevented tumbling. The 'lands' on Brenneke slugs purpose were to  allow the slug to pass through moderate choking without issue. While I don't have the technical knowledge to advise on why a rotating shotgun slug is better than one having more leading mass, it's apparent that most commercial manufacturers produce those of the latter type. True, sabbot shotgun slugs fired through riffled barrels claim to be more accurate, but at 125 yards, this differential accuracy may not be worth the cost. Suggest you contact a bullet swage die maker, such as one of the two Corbin brothers, as they have produced a few shotgun swage die sets in their 40 years of business. They may have your answers.

[Steve P]

Some of the "finned" slugs were swages with fins that appear similar to lands and grooves of a rifle barrel.  Wind caused the slug to spin and stibilize.  There are several choke makers out there that have rifled choke tubes to further enhance this spin.  You might check into a choke tube to help you out.

Steve

[SHOOTALL]

The fins on foster slugs are to allow the lead to compress if fired in a too tight choke .
A brenneke slug works like a shuttle cock not sinning but stablized by the felt wad on the end , fins for the same reason to keep from blowing up a bbl.
See if carlson makes a rifled tube or will make one . The one i have for 20 ga works great with foster slugs and sabots as advertised .And i don't see how either . They do have a unique rifling .

[Kmrere42]

It's been a while for this topic, been thinking about it.



If the slug has fins that have a twist to them. If there is not a tight seal behind the slug, the first thing that would happen is that the powder gasses would cause the slug to rotate in a counter direction to the twist of the fins. Thus the air resistance would have to first stop the counter rotation and then commence with proper rotation.

Also, Because slugs are shop at supersonic speeds, The shock-wave that is caused would not allow the air to pass smoothly over the slug and to apply force to the fins until the velocity had dropped to subsonic levels.



Paul

[MIBullets]

That is exactly why they put a backer type wad behind the slug, to form a seal.

[darkgael]

Gotta go with what has been said....the fins/rifling that one sees on swaged slugs is not there to spin stabilize the slug. It is there to allow for safe compression of the slug when someone fires one through a full choke.

The backer type wad, as on Brenneke slugs, does it fact form a seal. That is one of its functions. The other is to provide stability, to "weather vane" or "shuttlecock" the slug; that is why the things are permanently attached to the slug; if it were just a seal, there'd be no need to screw them together.
Pete