30mm Gau 8, 21" chamber end

[Chad G]

I am interested in making this project a breech loader using, powder bag and bullet with a percussion cap and external hammer on a rope, I'd really rather have a flintlock but for arguments sake percussion is simply easier for me to figure out.

I have looked for quite awhile for information with regards to turning the gun barrel end i have into a BP cannon and the most I have been able to come with is having the end threaded for a bigskysurplus end cap.  Or turning it into a DD and registering it - I wish to pass on that.

I don't have the money to pay a machinist to thread this barrel and it wont fit in my 12x36 lathe it is tapered and I have no way to hold it much less a threader that will work.  I have thought about boring out a couple of blocks of steel and making them lock up on the 3 ridges of this barrel and bolting or welding those plates together to keep them from moving.  I wouldn't be relying on the block to do anything other than supporting a breech door and the force generated by the explosion in the chamber. 

Another reason to bore out plates is so I have something to attach or make trunnions out of as I think it would be possible to slide the plates on the front and secure them using the same method as the rear support. 

I am quite sure I would need to shove a sleeve in the chamber to reduce its volumn and reinforce it.

My intent is to cast my own slugs be they bullets or round balls, leaning towards bullets due to the rifling in the barrel (progressive RH parabolic twist, 14 grooves).
My biggest concern is does type of steel matter in a case such as this? The barrel is whatever the US Air Force had them made from. I have what i think is hot rolled steel, its harder than crap to mill even on my 3 horse mill it eats my cutters up.

[Victor3]

 I'm not understanding why you can't hold it in your lathe. 12x36 is plenty big enough for a 21" piece. If the taper is a problem, can't you just grab the chambered end in the chuck, put a center in the tailstock, turn off the taper, then turn it around and chuck on the area you machined at the muzzle end?


 I have two of these barrels and can confirm that whatever they're made of is very tough stuff to machine. Should be able to single-point thread it with a carbide tool though.

[GGaskill]

I, too, have worked on this kind of barrel and had no difficulty threading with HSS lathe bits.  The US Army had several breech loading artillery pieces in service in the late 19th Century and other nations did, too, so there should be no problem finding a piece that meets the 1898 rule.  Here is one picture and this is another.



There are more detailed drawings available on the internet but with few dimensions so you will have to take the ideas and make your own manufacturing drawings.

[The Jeff]

There are more detailed drawings available on the internet but with few dimensions so you will have to take the ideas and make your own manufacturing drawings.

Modern Guns and Mortars Adopted by the United States Land Service has a chapter devoted to gun George posted. I've linked to the drawings, but if you scroll down to page 100, there's a list of principle dimensions that will help flesh out the drawings.

[Double D]

Complete description of the  Gun starts on page 93. 

[Ex 49'er]

Somebody at the shoots I used to attend here on the coast had a 30mm breechloader. He had about a 3" piece of the barrel and he poured lead into it to make his projos. Good luck with your build.

[Chad G]

My biggest downfall is the thru hole is only 1 3/8" dia, I don't own a lathe dog or a plate to correctly mate it to.  The lathe is a 1950's Logan, I also don't have a center or steady rest nearly large enough or stout enough to support it in.   I know I am probably making this harder than it is.  I'll go read the google article on the breech design, while i figure out how this is supposed to work in the lathe. 

[Frank46]

What you need is a pipe center for your tailstock. Depending on the morse taper for your tailstock will dictate which one you need. Check out the pipe centers on the enco website to get an idea of what I'm talking about and the size you will need. Hope this helps. Frank

[GGaskill]

What you need is a pipe center ...

Also known as a bull nose center.  Sample Enco bull nose center reference page.



It is also possible to make inserts for the muzzle which are center drilled and can be supported by a normal ball bearing center held in the tailstock.

[Frank46]

George, thanks for posting the pic of the bull nosed center. I sat here trying to think what it was actually called and only came up with pipe center. getting old stinks. Frank

[GGaskill]

Actually, I think you are really lucky to have the breech end of that barrel, which even by itself is strong enough for use as a black powder cannon barrel.  A breech jacket will add additional strength.  If the area with the interrupted threads is cylindrical from the back to the ring, I would turn off the threads (as I would be surprised if your lathe would cut that coarse a thread) and thread to 10 or 12 TPI.  You should check your lathe first, though, to be sure that it will not cut threads as coarse as those present before giving up on the partial threads already there.  Then make a matching breech jacket that contains matching threads and the interrupted threads for the breech block. 

A challenging project to be sure, but one to be proud of when successfully completed.

[shred]

And if you don't have the $ for a bull-nose center, you can do what the model boiler-makers often do and turn up a plug to fit the end of the tube, then center-drill that and use a regular center.

[Chad G]

My lathe will cut down to 4 TPI, with this much weight spinning I question the rigidity of my lathe.

 

 I haven't had much luck getting threads out of it though I've probably forgotten how over the years. I've mostly used this lathe to make small replacement gun parts that I can't buy. I really like the the partial threads on this barrel, ive tried to figure how I would cut an end cap to snugly fit over this as it is, and that its self is hard to figure out. Even if I manage to make it, keeping it on is another issue, I wish I could see how the Gau8 barrel locks into the gun carriage but my uncle is retired and getting onto the Air force base to get a glimpse of it is harder than ever. 

[GGaskill]

Your Logan looks very much like my Logan (except for the mess) and I would have no concern over doing the work on mine.  If you don't thread frequently, you certainly should get some scrap material and practice before working on the barrel.  Remember that you won't be turning the barrel at very high RPM when threading it.

Lathe dogs are pretty cheap; I think the real question would be whether you still have the original headstock sleeve that converts the spindle taper to #2 MT.  Centers by themselves are also pretty cheap.

[Chad G]

I didnt realize that photo still had the 3 jaw chuck on it........oops, I threw that out a year ago after being hit by a part that loosened from a junk chuck, I got a 4 jaw independent now.   I got these funky looking things that came with the lathe the guy didnt know anything about them, I think the taper thingy is for collets but I dont have 5C or 16C collets for it...or the other things to make one work Never ever used a lathe dog, not even in machines trade school.   

[GGaskill]

The sleeve I mentioned is a short piece with a 2MT hole and an external taper that matches the spindle taper.  I will post a pic of mine tonight sometime.  Post a pic of all the pieces you have but do not understand use of an we will help you.  Lathe dogs are relatively cheap and easy to use.  I expect there is a flat plate the fits the spindle and has one slot amongst your tooling.  That is the drive plate for a lathe dog.  I will include a pic of that, also.

Lathe dogs also are easy and really cheap to make.  Take a look at this one.



It is a couple of pieces of 2x4, a couple of pieces of all thread, one bolt and some nuts and washers.  I still have it and use it and have another smaller one for smaller work.

And, by the way, your lathe is way too clean.   

Spindle sleeve and drive plate.

[Dresden]

I worked where we made Gau-8 ammo, we would get a brand new barrel every quarter to test the tolerances with the projectiles, then it was cut up for scrap, I turned the muzzle end of a chunk of that barrel, I suggest Tangtung superG  tool bits and slow speeds. The pressure of the 30mm ammo cannot be duplicated with Black Powder, so you are extra safe with that barrel.

[Double D]

I worked where we made Gau-8 ammo, we would get a brand new barrel every quarter to test the tolerances with the projectiles, then it was cut up for scrap, I turned the muzzle end of a chunk of that barrel, I suggest Tangtung superG  tool bits and slow speeds. The pressure of the 30mm ammo cannot be duplicated with Black Powder, so you are extra safe with that barrel.

While it may be very true that the pressures of the 30mm  cartridge can not be duplicated with black powder, the statement that barrel is extra safe is only true as long as the barrel remains and is identifiable as a 30mm GAU,

Machined and turned into a cannon it becomes something else all together.  The maker and first owner may know what the source metal is, future owners will only know it is made of  "mystery metal".  Thus the encouragement to build to the recommended minimum safety standards.

The rifling will offer a clue to a higher grade steel, but what grade?

[moose53]

Making a Whitworth type breech for your barrel would work nicely . But matching the pitch might be a problem for your lathe , considering that its probably double pitch. The slap handle works very well at keeping things tight in use . It would also help to be comfortable with cutting threads so as  to do a good job .

[Dresden]

The breech you might want is a DeBang breech, here is a link to how it works:


http://archive.org/details/gov.archives.arc.89308

[Chad G]

I worked where we made Gau-8 ammo, we would get a brand new barrel every quarter to test the tolerances with the projectiles, then it was cut up for scrap, I turned the muzzle end of a chunk of that barrel, I suggest Tangtung superG  tool bits and slow speeds. The pressure of the 30mm ammo cannot be duplicated with Black Powder, so you are extra safe with that barrel.

While it may be very true that the pressures of the 30mm  cartridge can not be duplicated with black powder, the statement that barrel is extra safe is only true as long as the barrel remains and is identifiable as a 30mm GAU,

Machined and turned into a cannon it becomes something else all together.  The maker and first owner may know what the source metal is, future owners will only know it is made of  "mystery metal".  Thus the encouragement to build to the recommended minimum safety standards.

The rifling will offer a clue to a higher grade steel, but what grade?

My Uncle was US Air Force Rapid Munitions, he brought over for me for Christmas some 20 years ago, its been a toe stubber since then. 

Does anyone have sources for large Diameter rounds of steel, Enco is the only one I know of that sells 4140 rounds but they are expensive for a 6" section of bearing steel.  I made a right side plate for belt fed years ago out of 4140 plate it ate up my cutters.  I'll be leaving it like it is and not machining the outside for looks, GAU looks mean enough the way it is.

ETA: I'll just put this back in the closet for future plans.
 

[Double D]

There are any number of us sitting here drooling over this barrel and what we could make with it.  We do not want this thing turned into a Bubba cannon.

Here's my suggestion to you.   Get your self a piece of  1018 steel.  Get you self a set of cannon plans.  Build a cannon and learn how to use you lathe  and learn what a cannon looks.  4140 is not that hard to machine if you have the tools set up correctly. 

Here is a plan that would make a good learning product.



I made my first lathe turned cannon from those plans  and from 4140, thirty years ago.




Making the cannon will teach you basic turning, hole drilling, taper turning, some free hand profiling  as will as milling practice for making trunnion pockets. Get a copy of  South Bends How to run a lathe It's available as a print on demand book

 When you open that page if you click on Get this book in print  in the upper left corner and a drop down menu will open.  Click On Demand books and link to the Expresso book machine will open and you will find a list on demand printers.

While you are learning your lathe you can do some research  and find a cannon to replicate 

That reference the Jeff made to [Modern Guns and Mortars Adopted by the United States Land Service is a good one.  I already have a print on demand account with the  University of  Washington.  I ordered the book and had it in 7 days for $10 and postage. 

There some very basic rifled breech loaders in the book .  The drawings are not dimensioned but they are scaled.  It would be very easy to use a dial caliper and measure the drawings, put the dimensions in excel and scale then up to fit GAU barrel. 

You could make a very nice cannon that you could be proud of if you just take the time to learn.

[Chad G]

Okay I'll go down the small bore road and learn this stuff from plans and doing. Off to dixie gun works for breech loader plans.  I guess I shouldnt jump the gun so fast and try to dive in head first into a project I know so little about.

[Double D]

Forget the  Dixie plans  get the Plans from  AOP.  you will find them listed on the Cannon Links sticky a the top of the board.

Drop me a PM and I will send you a packet of plans, but you better hurry.  I'm leaving town Saturday and won't be back for a about ayear.