Need help with a Bofors 40mm breach.

[Brad Deckard]

The long bit is the sear, it is pushed into the spring, but it glides through the cams as well.
It needs to be pulled out . The manual does say it can get stuck a bit, I jemmy can be used to get it going.
I would suggest gently tapping the thin end in the middle of the circular spring housing to start it off.

Also at the other end of the sear is a small wheel which should rotate.( my bottom left photo.. in the bottom left of picture.. in the other photo im holding the wheel). this is separate to the removal of the breech but is like a little wheel which rolls over the side cover. Just for info.

When the cam is drawn out the sears will fall out of the bottom, as will the breech. It is relevant when replacing the breech if its cocked or not. If it isnt cocked there is a way of doing it. But replacement of the breech if its fired off is difficult. But get it out first and we can worry about getting it back in then.

(I have to add that my Bofors guns are all deactivated and certified by the London Proof House, and have the certificates and proof stamps on the cannons. Here in the UK we cannot own live bofors guns)

Brad

[Brad Deckard]

Your top left photo is the extractor removal bolt. If you unscrew it the extractor can be removed. You mentioned the barrel safety pin.. If the barrel is screwed in then this pin is not going to affect the removal of the breech.. If the barrel is out ( which yours is) then be sure you have disengaged this safety plunger. It will stop the breech removal. I am assuming you have disengaged it as you mentioned the barrel safety pin.
It mentions that in the manual.
Brad

[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