Traditional Rifling, another option???

[Oly]

I had a oppurtunity to daydream today ( second day of a training course ) and I was thinking - as rifling is set of twisted grooves (barrel) imparting spin onto a moving smooth object (bullet) why is it not possible to flip the roles? i.e. a moving object with a set of twisted grooves onit to impart spin (grooved bullet) from a smooth object (smooth barrel)??

 

Actually I've just now Wikipedia'd rifling and they say that "the GC-45 howitzer reverses the normal rifling idea by using a shell with small fins that ride in the grooves, as opposed to using a slightly oversized projectile which is forced into the grooves. Such guns have achieved significant increases in muzzle velocity and range. Examples include the South African G5 and the German PzH 2000."

 

In which case why is this not possible for rifles? That way the most appropriate twist rate could be applied to all bullet weights without having to scarifice accuracy or having another rifle. There must be a good reason otherwise we would have beaten the 'which twist rate rifle shall I buy??' question by now!!

[MarinePMI]

Oly,

 

I'd venture to guess that it only works to a certain level of pressure before the force would just push the round down the barrel with the round not having enough material resistance to cause the spin. Much like shotgun slugs with canted ridges that impart some spin to it.

 

Just a guess mind you, but I can't help but wonder if the yield strength of lead (or even copper) would be sufficient at high levels (55k psi +) to cause consistent rotation from shot to shot...

 

Anyone know what the chamber pressures are in a Howitzer?

[eldon]

Oly you wasn't on the 2nd day of a laser course was you? as I was.

[Guest varmartin]

I had a oppurtunity to daydream today ( second day of a training course ) and I was thinking - as rifling is set of twisted grooves (barrel) imparting spin onto a moving smooth object (bullet) why is it not possible to flip the roles? i.e. a moving object with a set of twisted grooves onit to impart spin (grooved bullet) from a smooth object (smooth barrel)??

 

 

The gasses would leak passed the projectile...or the grooves on the projectile would be forged flat as it passed through the smooth tube ??...end result ? an empty game bag !!

[Oly]

Eldon - no nothing so exciting sounding as that!

 

Varmartin - yes, just been down the pub to think it through properly and came to the same conclusion there. As you would also have to swap the hard'ness of the materials used too! ie instead of a soft bullet and hard barrel/rifling you would have to have a hard bullet/rifling and a soft barrel...so you may go throguh barrels pretty quick!!

[grahamfarmer]

i think whitworth the engineer of nut and bolt fame submitted a rifle for evalution with a army contract using a hexangoal sided barrel with a one revolution twist and a cartridge with a hexagonal bullet apparently outshot all other rifles submitted but was turned down as the bullets where not interchangeable with anything else some one built and fired one on discovery channel or similar to check the claims made for it

[Andrew]

i think whitworth the engineer of nut and bolt fame submitted a rifle for evalution with a army contract using a hexangoal sided barrel with a one revolution twist and a cartridge with a hexagonal bullet apparently outshot all other rifles submitted but was turned down as the bullets where not interchangeable with anything else some one built and fired one on discovery channel or similar to check the claims made for it

 

You're close. The hexagonal bullet had it's sides "twisted" to match the rifle. It was exceptionally accurate (the Southern Confederate States used them as sniper's rifles during the American Civil War) but it fouled miserably after only a few shots and the bullets required care in loading.

 

Mine will shoot 1.5MOA at two hundred yards with a cylindrical bullet: the bullet that finally gained acceptance in the Whitworth. When made of pure lead, sized to just kiss the "flats" of the barrel, and fired over an 80 grain charge of FFg powder, it will obturate enough so that the a recovered bullet will show six evenly spaced flats around the body of the bullet. Using this bullet requires that a heavy under wad be used to protect the bullet base and sides but it seems to equally as accurate as the difficult to cast and load hexagonal bullet. The Whitworth musket has an adjustable sear so that you can get a trigger pull that belies it's military appearance. It was really "hi tech" in it's day.

 

As to the finned bullet. I grew up using Brenneke slugs in a 12 bore for deer. Nothing to howl about. Cut my 100 yard groups from 8" to four. ~Andrew

[ds1]

Steyr developed the ACR rifle to fire a fleschette round (fin stablized). BC was +2.0 I think. Think it could hit a man size target from 0-600m without any elevation change required on the sight (mv @ 300m was +900m/s). The projectile looks like a dart with a plastic sabot.

 

Apparently it did not exceed the hit rate of the M16A2 by 100% so was not adopted in the US during trials in the 1990`s.

 

David.

[Oly]

Interesting - I wonder if this will ever be revisited as technology moves on?

[brown dog]

Actually I've just now Wikipedia'd rifling and they say that "the GC-45 howitzer reverses the normal rifling idea by using a shell with small fins that ride in the grooves, as opposed to using a slightly oversized projectile which is forced into the grooves. Such guns have achieved significant increases in muzzle velocity and range. Examples include the South African G5 and the German PzH 2000."

 

 

The dangers of wikipedia - the PzH2000 fires bog standard NATO 155 ammo (ie normal spin stabilised shells), from memory the G5 does the same (albeit, with Denel's interpretation of US 155 ammo).

 

If you go smoothbore you go fin stabilised -and fire a long projectile. Due to the insane velocities this can achieve (and you need insane velocities because the defeat of armour by APFSDS rounds depends on high KE) almost all tank guns are smoothbore.

[Ronin]

Hmmmn

 

 

"dear Firearms Licencing, I wish to apply for a .50 cal brown bess, that I intend to shoot depleted uranium, sabot projectiles to eliminate deer at insane ranges, using iron sights."

 

 

After that, I intend to apply for a "rail gun".

 

 

Seen footage of tank projectiles in slow mo, a few months ago on a Discovery programme - accurate to 3000 mtrs on moving targets and I think 5000+ fps

 

May be wrong there BD

 

 

Awesome technology and fascinating subject, though I doubt it will come into civilian hands in the form of smooth bores and saboted rounds in my lifetime

[Guest Tiff]

Ronin -PMSL- sod the 30-338, just drafting a letter to the plod now

 

As long as the sabot dart rounds expand, don't think there's anything in the law that says you can't have it for deer........................Plus there are considerable amounts of Uranium in the ground beneath my house So much so the old copper mines were reopened briefly in the war to look at the feasibility of extracting it!!

 

Do you reckon Lutz could make the rounds for me .