MLU FORUM  

Go Back   MLU FORUM > MILITARY VEHICLES > The Gun Park

Notices

Reply
 
Thread Tools Display Modes
  #1  
Old 03-01-18, 22:27
Jon Bradshaw's Avatar
Jon Bradshaw Jon Bradshaw is offline
Registered User
 
Join Date: Jan 2009
Location: Prince Edward County, Ontario, Canada
Posts: 264
Default Need help with a Bofors 40mm breach.

Anyone have a good working knowledge of the bofors 40mm? I have one that is a bit rusted and I can't get it to move/ function.
It has spent the last 2 months in a barrel of diesel and that helped but the main breach block is stuck hard in the open position. I have an operators manual on it and can't identify any parts that would account for it to be stuck.
I have removed the barrel and pushed the barrel safety pin back to make sure it is not locking it open.
I have freed up the trip ejectors and they are not catching the breach block.
I have tried hitting it, using a bit of heat to warm it up and even tried willing it to work...... but it has defeated me thus far.
The only thing I can see from the manual is that the inner sears are simply stuck with rust.... I can't see where the best place to tap on them is and have tried gentle tapping on everything I can see to try to get it to move.
I would also love to borrow some of the take down tools for a day to remove the parts that are free and give more access to the rest. The coil spring is still on it and that will be hard to remove without the proper tools.
If there is someone in my area (Edmonton, Alberta) I can meet with you in the next few days.
Attached Thumbnails
breach number.jpg   breach side.jpg   breach rear.jpg  
Reply With Quote
  #2  
Old 04-01-18, 12:59
Brad Deckard Brad Deckard is offline
Registered User
 
Join Date: Oct 2017
Location: United Kingdom
Posts: 38
Default Bofors breech help

That breech looks ok, you have to knock the sear out first which will release the spring and release the cams. Then the breech will drop out the bottom. , it may need a tap.. You dont need any special tools to remove the coil spring. But DO NOT attempt to dismantle the spring housing as its under tension.

You will need a crow bar for a lever and a drift and a hammer.. But if your wacking it like hell your doing something wrong..

I will get some photos on here to help you.
Brad

Last edited by Brad Deckard; 04-01-18 at 13:25.
Reply With Quote
  #3  
Old 04-01-18, 13:16
Brad Deckard Brad Deckard is offline
Registered User
 
Join Date: Oct 2017
Location: United Kingdom
Posts: 38
Default bofors breech help

http://www.mapleleafup.net/forums/at...1&d=1515068147
Attached Thumbnails
IMG_3958.JPG   IMG_3961.JPG   IMG_3962.JPG   IMG_3960.JPG  
Reply With Quote
  #4  
Old 04-01-18, 13:23
Brad Deckard Brad Deckard is offline
Registered User
 
Join Date: Oct 2017
Location: United Kingdom
Posts: 38
Default Bofors breech help

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

Last edited by Brad Deckard; 04-01-18 at 13:29.
Reply With Quote
  #5  
Old 04-01-18, 13:24
Brad Deckard Brad Deckard is offline
Registered User
 
Join Date: Oct 2017
Location: United Kingdom
Posts: 38
Default your top left photo

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

Last edited by Brad Deckard; 04-01-18 at 13:32.
Reply With Quote
  #6  
Old 04-01-18, 13:43
Brad Deckard Brad Deckard is offline
Registered User
 
Join Date: Oct 2017
Location: United Kingdom
Posts: 38
Default

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..
Attached Thumbnails
IMG_3964.JPG  
Reply With Quote
  #7  
Old 04-01-18, 17:39
Jon Bradshaw's Avatar
Jon Bradshaw Jon Bradshaw is offline
Registered User
 
Join Date: Jan 2009
Location: Prince Edward County, Ontario, Canada
Posts: 264
Default Thanks Brad.

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.
Reply With Quote
  #8  
Old 04-01-18, 18:01
rob love rob love is offline
carrier mech
 
Join Date: Feb 2003
Location: Shilo MB, the armpit of Canada
Posts: 7,517
Default

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.
Reply With Quote
  #9  
Old 05-01-18, 06:42
Jon Bradshaw's Avatar
Jon Bradshaw Jon Bradshaw is offline
Registered User
 
Join Date: Jan 2009
Location: Prince Edward County, Ontario, Canada
Posts: 264
Default so it took all day....

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.
Reply With Quote
  #10  
Old 05-01-18, 13:03
Brad Deckard Brad Deckard is offline
Registered User
 
Join Date: Oct 2017
Location: United Kingdom
Posts: 38
Default 40mm gun

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

Last edited by Brad Deckard; 05-01-18 at 16:06.
Reply With Quote
  #11  
Old 05-01-18, 19:36
Jon Bradshaw's Avatar
Jon Bradshaw Jon Bradshaw is offline
Registered User
 
Join Date: Jan 2009
Location: Prince Edward County, Ontario, Canada
Posts: 264
Default Rammer?

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.
Reply With Quote
  #12  
Old 05-01-18, 22:02
Brad Deckard Brad Deckard is offline
Registered User
 
Join Date: Oct 2017
Location: United Kingdom
Posts: 38
Default rammer

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

Last edited by Brad Deckard; 05-01-18 at 22:11.
Reply With Quote
  #13  
Old 06-01-18, 00:19
Jon Bradshaw's Avatar
Jon Bradshaw Jon Bradshaw is offline
Registered User
 
Join Date: Jan 2009
Location: Prince Edward County, Ontario, Canada
Posts: 264
Default No, exactly the opposite....

Brad

What you see is what I have and all I need. The barrel end is only 15inches which is barely longer than the breach. This is going into the turret of a (reproduction) 1936 Vickers light tank in place of the 2pdr that should have been in it. All I wanted was a working breach, I will modify what I have to suit the turret mounting. The rammer tray you speak of was broken off of mine and the part that was attached has already been removed at the take down pin prior to the pics.
I just needed a working breach so that's all I bought.
Reply With Quote
  #14  
Old 06-01-18, 12:26
Brad Deckard Brad Deckard is offline
Registered User
 
Join Date: Oct 2017
Location: United Kingdom
Posts: 38
Default I understand

Now I understand... Apologies I was in Bofors mode!!
As you say you will need to modify it to fit and function...
I am glad that you got it stripped down...
Send me a photo when you finish the conversion..!!
The breech will fire off when closed, I am sure it can be modifed to not fire.
You could also message that chap on the film you shared here and ask him how he holds back the pin..
Glad I helped you up to now..

Brad
Reply With Quote
  #15  
Old 20-11-18, 04:44
pekelney pekelney is offline
Jeff
 
Join Date: Oct 2010
Location: San Francisco, CA
Posts: 7
Default bofors manuals should help

I have found both of the these manuals helpful, esp. when you can disassemble in the order suggested:

https://maritime.org/doc/boforstm252/index.htm
https://maritime.org/doc/boforstm/index.htm

The illustrations are better in the Navy manual:
https://maritime.org/doc/bofors40mm/index.htm

rich
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Sold: 40mm Bofors accessories. rnixartillery For Sale Or Wanted 3 09-11-16 15:36
40mm Bofors Question herr-pear The Gun Park 42 15-10-14 16:25
For Sale: 40mm Bofors Rounds Brad Mills For Sale Or Wanted 0 05-05-13 14:30
40mm Bofors on oz ebay Ryan For Sale Or Wanted 8 11-01-08 04:50
40mm Bofors Rounds Brad Mills The Gun Park 19 26-08-07 14:52


All times are GMT +2. The time now is 12:51.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright © Maple Leaf Up, 2003-2016