SpudFiles

has this been done before? modifying the threads on a breech or end cap to be a push and turn cannon

I recognize the possible problems like the seal, simply use a rubber washer seal like on a garden hoses or to some degree a soda bottle. the other thing the strength and and friction on the threads, so clean out the threads and use a stronger material

examples of push and turn

yes I know it big

It would take a bit more care to line it up with tapered threads, but if you added a seal, it would work.

Just make sure there is enough thread to held the cap in place without blowing out.

Ive never seen it here on spudfiles.... BUILD ONE!
Im afraid for leaks when using this but it should be able to work when done the right way.

okay I just did, I applied it to a soda bottle combustion, I tested it with a tight bore fitting projectile and it worked fine but my ears are still ringing from the sound of the blast

I messed up once, you got to mark were your cutting the threads on both parts based on the position it's in when its tight

I'll have to get pics when I find my camera's usb cable

I seem to recal that someone has done this for the cleanout plug on a combustion gun. Latke perhaps? They started with generic cleanout adaptor and plug and removed part of the threads from each so you could insert the plug and give it a quarter turn to seal it.

I would worry about the strength of the modified cleanout. Cleanouts are not generally pressure rated to start with and removing 50% of the threads isn't going to make it any stronger.

Whyy introduce the complexity of threads when you can have simple locking lugs as in a bolt-action rifle?

image ddint work jack....nor does copying and pasting the url...

It seems a fair bit more complicated than actually need be.

jackssmirkingrevenge wrote:Whyy introduce the complexity of threads when you can have simple locking lugs as in a bolt-action rifle?

Perhaps for the same reason the cannons in the original post used threads instead of locking lugs?

A 3" diameter cleanout operating at 60 PSIG max pressure has ~400 pounds of force on it. For a 4" cleanout it is ~750 pounds of force.

Besides, in a bolt-action rifle isn't the chamber sealed by the cartridge and not the bolt? The bolt provides the holding force but the actual gas seal is created by the casing. In the absence of a cartridge case the bolt-action mechanism has to provide both the holding force and the gas seal.

A threaded breech plug could provide the seal. Of course, if you are hacking threads out of a cleanout it's ability to seal is probably pretty well destroyed.

jackssmirkingrevenge wrote:Whyy introduce the complexity of threads when you can have simple locking lugs as in a bolt-action rifle?

because these threads are good for plug type breeches and applications, bolt actions required a specific length of space for the bolt, and the ammo can only be as long as the bolt stroke's lenght,

an example of a good plug application would be venting/loading/cleaning a coaxlie combustion

A threaded breech plug could provide the seal. Of course, if you are hacking threads out of a cleanout it's ability to seal is probably pretty well destroyed.

which is why you have a sealing face like in my soda bottle prototype

iknowmy3tables wrote:

A threaded breech plug could provide the seal. Of course, if you are hacking threads out of a cleanout it's ability to seal is probably pretty well destroyed.

which is why you have a sealing face like in my soda bottle prototype

Of course, you still have the problem of weakening a part that is already only marginally capable of doing what it is supposed to do, that is, withstand the force exerted on it by the combustion process.

A "quarter-turn" breech plug would be really cool, certainly make cycling the gun a lot easier. I just wonder if it can be done safely.

which is one of the problems, however there are solutions like the cap with sch40, a diffrent thread gauge, or a diffrent material
for a mini combustion soda bottle threads are more than safe so I had no problem with hacking at it

It's still surprising that few have tried this