Bofors barrel what t I do what to do??

[cannonmn]

Here's an article with some images:
http://riv.co.nz/rnza/hist/gun/rifled2.htm

[Cannon Cocker]

Here's the exact shape, and you're right it's only mostly hexogonal, really 12 sided with small flats at the corners of the hexagon.

[guardsgunner]

  When I was looking at making a Whitworth, I concluded that the easiest way to do rifling, was to cut 6 deep grooves then remove the angles on either side of the grooves.The twist rate on the 3 pdr. was faster the Bofors at 1/48. Whitworth tried everything down to 1/10.
 
  It looks like the one in cannonmn's pictures must shoot a thick walled cartridge judging from the veiw from the breech.
 

[cannonmn]

 

It looks like the one in cannonmn's pictures must shoot a thick walled cartridge
judging from the veiw from the breech.
 

Correct.  Comes with about  20 heavy aluminum cartridge cases.  They were made so the projectile sets completely enclosed in the front end of the case, and the case butts up flush against the shoulder (rear surface) of the chamber.  That way the projectile doesn't have to jump anywhere that it isn't supported all around, and will not have a chance to get off-axis. The cases have a wide shoulder that the projectile base sits on, and the powder cavity underneath is a fairly long, "subcaliber" hole.  The wall thickness of the case is about 1/2 inch for the approx. 6 in. long cylindrical powder cavity.  The rear of the case has an axial hole, lined with steel, I think, to carry the primer flash to the powder cavity.
The designer/builder of the repro put a great deal of thought into this piece.  His carriage is a copy of the one shown in the photo I published "Whitworth 3 pdr. Experiment Liverpool" with independent upper-carriage traverse etc.  I think everyone's seen that photo.     

[Joey V.]

DD,

I'm not writing a letter for a parrot letter it's just a pure muzzleloader with external fuse. Or should I write on that too?
When / if I get approvals should we post the reply letter here publicly for the huges cannon?
Thx! Guys

[Double D]

When I saw this picture I thought at first glance he had modifed the entire barrel.

[guardsgunner]

Joe,
  The hughes gun does not meet any of the requirements that could be against the law.(presently) The parrot either.
pre 1898 design , no available cartridge, external prime, ect.
 Some times it is just better not to poke at the bear.
 
Bob
 

[Cannoneer]

When I saw this picture I thought at first glance he had modifed the entire barrel.

So did I, but I still don't get it; is this a live firing cannon, or did this guy turn a rifled barrel into a salute gun?

[Double D]

DD,

I'm not writing a letter for a parrot letter it's just a pure muzzleloader with external fuse. Or should I write on that too?
When / if I get approvals should we post the reply letter here publicly for the huges cannon?
Thx! Guys

I  don't understand why you you think you  need a letter for the  Hughes gun.  It  clearly meets all the criteria for an antique cannon.

I wouldn't waste my time on it, just get building.   

Where you need a letter is if there is a gray area such as the Long Cecil I will be building when I get back.  Long Cecil was built in 1899, so a replica doesn't meet that criteria as replica of an antique.  I will use loose powder and fuse ignition-an antique ignition system.
 
Most folks don't understand that antique exemption also applies antique ignion sytems.  So to cover bases I got a letter.  In your case the Hughes is pre 1899 or made in or before 1898.  It is an antique design per the law.  You shouldn't need a letter-unless you just want to cover bases. 

[cannonmn]

So did I, but I still don't get it; is this a live firing cannon, or did this
guy turn a rifled barrel into a salute gun?

Since the builder has passed on into the land of free blackpowder and unlimited ranges, he won't be able to tell us.  Within proper firearms terminology, it is a "false muzzle."  However in this case it doesn't have any mechanical function, but is purely decorative.  I think the builder wanted his gun to look like a real b/l Whitworth all over, and to do that he took care of the last un-Whitworth-lookong detail by making the false muzzle.  Seems simple to me.
BTW, can you tell how he made the false muzzle?  Clue:  There is no source of internal-octagon-cavity bar stock, so he had to make it from scratch.

[The Jeff]

BTW, can you tell how he made the false muzzle?  Clue:  There is no source of internal-octagon-cavity bar stock, so he had to make it from scratch.

I would put 60º bevels on 6 pieces of thick flat stock and weld them together. Then turn down the outside and attach to the Bofors barrel.

[cannonmn]

I would put 60º bevels on 6 pieces of thick flat stock and weld them together. Then turn down the outside and attach to the Bofors barrel.

That's probably essentially what he did.  He finished all surfaces so evenly that where one piece ends and another starts is very hard to tell.
He may have started with a hex mandrel skeleton made of a hex plate at either end, and held it at the ends, then clamped the bevelled plates to the outside of it while welding to hold the alignment.

[Cannon Cocker]

  When I was looking at making a Whitworth, I concluded that the easiest way to do rifling, was to cut 6 deep grooves then remove the angles on either side of the grooves.The twist rate on the 3 pdr. was faster the Bofors at 1/48. Whitworth tried everything down to 1/10.
 
 

Actually the twist rate on a Bofors 40mm with a 1.57" bore is a gain twist starting at 45 and ending at one in 30".  The 3 pounder Whitworth with a bore of land diameter 1.7" (or 1.5" on Johns possibly original experimental model) is on turn in 40". 

[Joey V.]

DD,
Your right about the letter thing. I won't poke the lion and just play it by the rules of the pre 1898 with external primer laws.  Besides the atf has enough to do soon with the upcoming bans and gun grabs...

Thx again!

[shred]

FWIW, it is possible to buy internally-broached hex sleeves in smaller sizes (this particular one is 1.25" ID or so: http://www.reidsupply.com/sku/HHS-124/) .  I've never looked for larger ones.

[KABAR2]

FWIW, it is possible to buy internally-broached hex sleeves in smaller sizes (this particular one is 1.25" ID or so: http://www.reidsupply.com/sku/HHS-124/) .  I've never looked for larger ones.

This would make the job a lot easier.... just did a search and it seems the largest made industry wide is 1.25....... but the search gave me some other items of interest from an engeering standpoint... so all was not a waste of time looking...
I had the privlidge of looking over Cannonmn's reproduction Whitworth some time ago and the builder did a fine job, the muzzel is very convincing as you walk up on it.... Is the original residing on the carraige now?

[cannonmn]

Is the original residing on the carraige now?

It is going to the carriagewright to have one wheel restored and to do any necessary fitting of carriage to tube, only waiting to see who has a road trip in the others' direction first.

[michaelfreeland]

Still working on mine. The shop that has it says they are 'too busy" for now, which is fine, since it's getting expensive. By the time the carriage is finished this will be a 6K+ adventure