Need help with a Bofors 40mm breach.

[Brad Deckard]

If I have miss understood you and it is simply stuck.. and wont budge, this is the little sear on the bottom of the breech which hold the pin back.. it could be in the wrong place and need pushing over to release the firing pin..

[Jon Bradshaw]

After looking at your pictures and reading your comments I went out and tried again. I was trying to hit the shaft towards the spring instead of away from it. Beyond that I applied more force to the cam shaft and it did come out but with some serious resistance. This breach has not functioned in over 30 years that I know of and who knows how long before that.
The cams and the breach block are still rusted solid in place and I can not see any way to apply adequate force to them if they are stuck as solid as the cam shaft.

[rob love]

At this point, get it into a press rather than hammering it. Hammering will leave marks....a press will move it. You can also make something with a bottle jack and some chain and wooden blocks, but I would recommend the press.

Place a block of hardwood onto the block so the press doesn't leave it's mark.

When I did my 25 pounder, I ended up using the 75 ton press at work, and while the pressure gauge doesn't work on our press, I was up in the higher end of force. Once the rust "cracked", it was smooth sailing after that. Make sure you have a hunk of plywood on the floor for when the breech block finally falls out.

If you can get it in to your maintenance shop, they will have the right press for the job.

[Jon Bradshaw]

I now have a clean and functioning breach. It took all day and involved a few blocks of wood a sledge hammer and some ingenuity.
I cleaned the parts and put them back in to check for function and the bolt fired once it reached top position as expected.
Since this is not going to be in an auto firing "AA" setup but in a tank gun installation this is not ideal for me. Is there a common mod to stop it from firing once it closes or is this something that I will need to make from scratch?
I need to mod out a trigger for it along with this so I am curious if it has been done by anyone on this forum before?
I found this on you tube and it seems to be exactly the mod I am trying to do.
www.youtube.com/watch?v=WzR7pV_sAmU
I will put up some more pics once it is all clean and shiny.

[Brad Deckard]

Glad you got it sorted...

The Bofors gun was very well known to take fingers off. The way that chap in the video closed that breech... wow.... he is lucky not to loose fingers. As you know the ejection cams fly forward when the round is chambered, this releases the bolt, which SLAMS upwards and auto fires.

The bofors is an auto cannon, so is designed to fire .. ie firing pin forward, when the bolt slams upwards.

There is a single shot mode on the side, Can you not use the rammer to load and fire it in one action.. ie drop a round in and release the rammer.. It will ten fly forward and load the round and fire it in one movement.

I have got spare rammers if you need one somewhere.

Brad

[Jon Bradshaw]

Brad

I am not sure what you mean by a rammer, I know what they are but can you post a picture of one made for a bofors? I would think a small dowel of wood with a cloth or leather covered end would suffice.
Also if you notice in the video he has removed part of the barrel lock to make it safer to hand load, the part that comes back onto the breach block has been removed. Mine has this bit but I will likely do the same and cut it off.
It looks like he has set it up on some sort of pull cable squeezable trigger. I can only see that working if you modify the cam and weld a bit on the bottom of the block to give you a new trigger..... I will puzzle this out.
Thanks for all the help so far.

[Brad Deckard]

The Rammer is a large heavy spring loaded tray which fits in the bofors casing.. The round falls through the gates and lays on the rammer, Its then thrown forward when the gun is fired and rams the round into the chamber..

How much of the bofors do you have?

The rammer pins onto your breech, if you look at your top photos, top right photo on the right there are two holes which take the rammer securing pin.

The rammer pins on here and is a large gun metal tray with a spring inside and claws which throw the round into the breech.

How much of the cannon do you have? Do you have the housing which takes all these parts? You top photos show the breech casing, do you have the bit that it slides into.. including the cocking lever and selector lever?

I Am guessing you have an entire bofors cannon minus a mount?

I can photo a rammer tomorrow if you want to see one.

Brad