Is there any good resources out there on cannon breech designs?

Yes.

My personal favorite is of course Rheinmetall's Handbook on Weaponry but H. Peter's Armament Engineering and Principles of Armament Design are both fantastic resources which focus more heavily on larger designs.

I also heartily recommend the Brassey's Essential Guide to Military Small Arms: Design Principles and Operating Methods.

If you're on a budget just stick with the Rheinmetall handbook which can be found as a PDF here. Pick one of the mirrors and get to downloading.

What he said ^^^

Those are great resources.  And have been used to create a number of new 20mm and even 30mm cannons

I also take pictures of every cannon, howitzer,  and tank gun i run across and save them in a folder for inspiration/ideas. I spent hours walking around Fort Hood lol

They've been used to create a lot more than little popguns too. Rheinmetall's L52 155mm main gun was designed along the same principles seen in those books.

I think the largest I've seen made privately is likely a 105mm. You can go pretty simple by throwing enough good material at a design and having a decent starting point.

ETA:


Do share with the class please!

Thanks!  I looked up Brasseys and dang, $400

Yeah - and that's a much lower price than I paid. They came down over the last few years now.

If you're willing to shell out the money I highly suggest the two H. Peter books. He goes into the math and the reasons behind it.

After reading those two titles you damn well can design any large caliber gun you can get powder for. It's that thorough.

However - the free PDF I linked of Rheinmetall's Handbook should be able to guide you down the path. The math and the refining of the ideas are both on you at that point but it's doable.

Damn had no idea my Brasseys was worth so much now. I also have an original copy of Rheinmetallbook from when you could write them and they would send you a copy for free.

You might also find a pdf copy of DARCOM 706-253 Dept of the Army, Engineering Design Handbook, Breach Mechanism Design, from 1979
I downloaded a copy from http://www.everyspec.com along with design handbooks on muzzle brakes, gun tubes, carriage/mounts and recoil systems, automatic weapons, and internal ballistics.


These you might also find useful:
TM 9-3305 - Principals of artillery
TM 9-1311 - 75mm cannon manual
8in ww2 gun manual
37mm ww2 gun manual

I had completely forgotten about the Breech Mechanism Design from 1979! Excellent suggestion.

I downloaded the TM’s, but haven’t had time to really look over them. Thanks for the advice guys!

Brassey's is free online, as is the Rheinmetall Hanbook, the Oerlikon Pocketbook, and many others.

Has any body gotten any further than just getting the hand books? I picked up a 37MM barrel and would like to make a breech for it. I'm  reading the books now.

What kind of barrel did you get. On of those Russian AA barrels? Or something more common like an m3 or m6 barrel?

Yes one of the M1939 AA gun barrels. Looks to be new for as old as it is.

What always worried me about making a breach for a cannon, is that almost universally they were all forged to get the steel grain structure to line up with the breach design. Making a block from a large hunk of billet steel would not have that so the design would have to incorporate the possible fatigue and stress concentration issues into the design.

Well that all depends on the engineering.

You could forge one though with a skilled blacksmith and a big enough power hammer

I will agree that forging is stronger on the same steel alloy as non forged parts. But we don't have to use the same steel alloys they did in the 30's-40's. There are much stronger steels now and readily available.  Lets face it a lot of stuff was worked hot because we didn't have the machinery to make the shape we wanted easily. Even the machining prosses has changed to make designs stronger. And of course you don't have to fallow a design to the thousands.

I contracted a structural engineer, in addition to speaking to the owner of a heat treating facility, and after they both looked at my cut L7 breech ring they both had the opinion that the ring was WELL over-engineered for the job it performs.  We had both portions of the ring Rockwell tested and the owner's opinion that it was probably high quality steel, it was "soft" enough that any filler material would be of the same hardness. The engineer used some sort of (I apologize I don't know the name of it) hand-held laser spectrometer. It was able to tell us the exact make up the steel so we could get a filler rod that would be the closest to the original material. A master welder did prescribe the manner it had to be welded (constant temperature, maximum heat, hammering the weld while still molten, etc) so I would have "certs".

Long story and lots of time later, we welded it back up to the prescribed specs. My guys are very competent welders and I wasn't concerned about their skills but it did feel comforting when they cut off the "over lay" and not one single void was found in the face of either pieces (about 6"x3").

Point being, I know that grain structure is important in regards to forged and billet steel but after talking with people much more knowledgeable about engineering than myself, I wouldn't hesitate to make a ring or weld another (provided that smarter individuals give precise instructions).

Here is our L7A3 ring and the second picture was it's first firing since being reborn.

V/R
Ron

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Just wondering, did you have the weld x-rayed?

I am a mechanical engineer in the firearms business but not a metallurgist so without looking into the designs further I am just hesitant. That and the few catastrophic failures of breaches in civilian hands have just made me weary. You also might want to ask your structural engineer if he took impact and fatigue loadings into his design review of the breach. Simple pressure loads are easy to take into account, its the fatigue and impact that can get you in trouble.

When I worked in the petrochemical industry we used an x-ray diffractometer to determine unknown types of steel in older pressure vessels. That and hardness testing would usually give us a range of materials but without cutting out an test coupon and sending to the lab for tensile and shear tests we could not determine down to specific grade of material used. Its been over 10 years since I was last involved with such endeavors so I do not know what the latest methods nor do I know their accuracy any more.

BTW Good looking tank. If the L7 a bag gun? or cased ammo?