Prewar BSA double sear trigger problem

[stevegv8]

Hi Steve,

The reason the pinned one has one spring is that it only needs one, to see what is going on inside it's easy to use the trigger block pivot as a guide and mock up something if you have access to some tube / bit of box. This sort of thing;

https://www.flickr.com/photos/312284...7626485415532/

Or you could maybe make something to hold you action onto a base etc.

Here I set a CD unit on a BSA I modified at the height and position it would be to check sear engagement with a piston rod, so just attach a bit of tube or scrap cylinder to a base, then set up your trigger with a spacer so it's the right height and you will see exactly what is going on as the piston moves back, It is quite enlightening to see how the piston rod ramps over the sear / trigger and then latches when you do this.

The whole double sear system is a rare example of an unnecessary safety (the guns are safe with the tap open) attempt by BSA which was obviously not tested long term, as so many are seen that have been riveted up. When all is good it works well enough, but I doubt guns with the system working get the hard use a gun would have back in the day which obviously brought the problem to light to the dealers / factory.

Pretty much summed up by the fact that the factory "fix" was to disable the whole shebang....The problem getting them to work is also getting the spring balance correct, I have done two or three and it's a pain but can be done (I had a Juvenile which arrived with problems which took ages clipping springs etc. to get the right balance as springs are NLA).


ATB, ED

Very useful thank you and a really nice job by the way.
Not that it really matters why mine's how it is, but I'm pretty sure now someone needed to change the piston in the past, used a single sear type and ran into issues from doing so then started cutting and shutting getting in deeper to the point it was given up on.
At the end of the day if possible I'd like to return it to how it's life began but happy to convert (properly) to single sear set up if need be. It all hinges on what parts I eventually track down.
I'm not going to restore the finish though, I merely want to get it back to a functioning state.
Right now I'm mainly trying to establish if only the rods differed between the two pistons so a two notch rod can be made to put in this piston or not as I can get a rod made locally otherwise I need a correct piston and sears pair.

Steve

[stevegv8]

The plot thickens as they say.

I have now found since I have all the parts back that my piston is such that it would never have worked in this gun.
I had surmised that it was a replacement (with one notch only it has to be) and a sear was removed expecting to make it work yet didn't work.
Having seen photo's kindly sent to me by Huttles94 my piston and the one from his gun differ in length & design greatly.
My pics should show my one notch piston is much longer and has a skirt extending where Huttles94's does not (would like to know what mine is originally from).

I have learned along the way there were two sears, the two spring type & the later one spring only and rivet (pin) alteration, used in juvenile and Model D's.
So this raises a question in it's self to me though, that being as the cylinder length and bore(?) might differ between two such models then piston length/design might differ between them too. Obviously I must find a particular one notch piston so is there more than one choice?

The only other thing that comes to mind at the moment is how far did they go at solving this? and therefore do I still have the right cocking link?

Huttles94 is kindly sending me a double sear to get me one step closer.

His photo's give me the length info & having pestered him for the piston O/D size I realise as my piston fits the cylinder I already know that, so I will have to post in wanted for the correct piston or loan, of such, a tall order but finding a sear was and Jake had one, top man.

Pic of Huttles94 piston at a fraction over 6 inches and my one at over 7 inches (would normally be a nice brag).

https://imgur.com/gallery/dYwiNRt
Steve

[edbear2]

Yours is the post WW1 extended skirt piston as fitted to the 45" guns, see here at bottom of group;

https://www.flickr.com/photos/312284...7607860743867/


The piston body castings are the same otherwise, it might be you just need to remove the "Skirt" on a lathe........The latch rod however has the notch in a different place, ie. the pre 1919 guns ("sporting" and early standard) were a slightly longer stroke, hence why they often make full power compared to the 1919-39 guns of the same size.

The piston rods can be removed as threaded witha keeper screw.


HTH, ATB, Ed

[stevegv8]

Yours is the post WW1 extended skirt piston as fitted to the 45" guns, see here at bottom of group;

https://www.flickr.com/photos/312284...7607860743867/


The piston body castings are the same otherwise, it might be you just need to remove the "Skirt" on a lathe........The latch rod however has the notch in a different place, ie. the pre 1919 guns ("sporting" and early standard) were a slightly longer stroke, hence why they often make full power compared to the 1919-39 guns of the same size.

The piston rods can be removed as threaded witha keeper screw.


HTH, ATB, Ed

Hi edbear2, that's interesting and more useful information!
When trying to understand the history of why this gun has these bits, was it maybe years ago someone thought swapping the piston could be a power increase and then as it all unfolded more and more problems arose ? Anyway as I've said further up it's all speculation and I'll never know for sure, what matters is making it function again by fitting correct parts or a modification of some sort.

I also said previously I had originally hoped to fit a correct rod to it whether I could obtain one or copy one but then found my piston to be much longer from the pics of a correct one I was sent. Leaving me at that point assuming I needed another piston/rod complete of the correct type but I had wondered if removing the tail end might be a way to go. Although with no correct one to hand I couldn't be sure the reduction could be possible without eating into the tail end that contacts the cylinder but it does appear the extended skirt is what makes it longer. Again though without one to offer against mine would the cocking link groove be in the exact correct place and length for instance?
So still waiting to see what options turn up.

Steve

[edbear2]

Hi edbear2, that's interesting and more useful information!
When trying to understand the history of why this gun has these bits, was it maybe years ago someone thought swapping the piston could be a power increase and then as it all unfolded more and more problems arose ? Anyway as I've said further up it's all speculation and I'll never know for sure, what matters is making it function again by fitting correct parts or a modification of some sort.

I also said previously I had originally hoped to fit a correct rod to it whether I could obtain one or copy one but then found my piston to be much longer from the pics of a correct one I was sent. Leaving me at that point assuming I needed another piston/rod complete of the correct type but I had wondered if removing the tail end might be a way to go. Although with no correct one to hand I couldn't be sure the reduction could be possible without eating into the tail end that contacts the cylinder but it does appear the extended skirt is what makes it longer. Again though without one to offer against mine would the cocking link groove be in the exact correct place and length for instance?
So still waiting to see what options turn up.

Steve

Hi Steve, the pistons are the same except the rod, the cocking slots are the same etc.........just remove your extension (look at the photos carefully).......Your piston then will be as fitted originally except for the location of the piston rod notch (again as per photo)....all this assuming your gun is 45" long obviously.


I expect the piston was changed because the trigger group was playing up, and then someone started filing things, perhaps both the sear and rod, to try and get it to work... I have seen two or three double notched rods that have been really "got at" in attempts to make them work, just an idea.

ATB, Ed

[stevegv8]

Hi Steve, the pistons are the same except the rod, the cocking slots are the same etc.........just remove your extension (look at the photos carefully).......Your piston then will be as fitted originally except for the location of the piston rod notch (again as per photo)....all this assuming your gun is 45" long obviously.


I expect the piston was changed because the trigger group was playing up, and then someone started filing things, perhaps both the sear and rod, to try and get it to work... I have seen two or three double notched rods that have been really "got at" in attempts to make them work, just an idea.

ATB, Ed

Yes agree, something was done which led to further yet unsuccessful work no doubt.

Now there is hope again because I was going to have the loan of a double sear to copy from somebody's gun. Not needed now as I have a double sear on the way but if I ask to loan the piston instead I can then get accurate data to have the piston altered and a rod copied. Just holding on a short while in case anyone offers what I need from my wanted post, unlikely I know but the sear did show up as available!

Here's hoping.

Steve

[Shed tuner]

As an aside, I find the .22s shoot better with the rear piston skirt extension removed - takes off a good deal of weight, and makes is less slammy.