improved model B

[j_potter]

hi all. I recently acquired a nice improved model B in good condition and all seems mechanically very good. the problem is I can't get the trigger sear to catch when I try to cock it. is there some special knack to this ? I've tried adjusting the trigger adjuster screw to all positions from fully out to fully in. also, does anyone know where I can get a parts diagram ? desperate to try shooting this ! many thanks, joe

[Garvin]

hi all. I recently acquired a nice improved model B in good condition and all seems mechanically very good. the problem is I can't get the trigger sear to catch when I try to cock it. is there some special knack to this ? I've tried adjusting the trigger adjuster screw to all positions from fully out to fully in. also, does anyone know where I can get a parts diagram ? desperate to try shooting this ! many thanks, joe

Joe check out this advice:

http://www.network54.com/Forum/67044...ailure-to-cock

Various pre-WW1 triggers shown here:

http://www.network54.com/Forum/67044...exploded+views

[j_potter]

many thanks for this danny, it's just what I need. the trigger return spring is in place and the cocking arm assembly all looks fine. at full extent of the cocking arm the trigger moves but it feels to me as if it needs to travel a tad further for the trigger sear to catch. i'll take a big gulp and start taking it to bits ! i'll let you know how I get on. I can't believe it's taken me this long to buy one of these, it's a lovely bit of engineering.
all the best
joe

[j_potter]

well gents, i'am now totally mystified !!! I've taken it apart down to the piston. the trigger sear and the notch on the piston rod are good and sharp and fit together nicely. there are no bent or broken parts and no extra washers or shims anywhere that I can see. it obviously has been used in the past but there is minimal wear on the engaging surfaces. I would say ( i'am a retired engineer ) that the piston needs to travel further back on cocking to engage the trigger sear but i'am loath to start filing anything. any ideas gratefully received ! joe

[frogboy]

I suggest you contact Edbear2

He has helped me no end with some of the awful guns I've bought on a whim.

I know that with one, his prognosis was that in order to "lighten the trigger" a common amateur fix was to file the sear, this eventually leads to a trigger that releases unexpectedly or won't engage and hold at all.

Lee

[frogboy]

the other thing i can think is has the spring been replaced? If so some of the replacements are far too long leading to them becoming coil bound before the piston can latch onto the trigger

good luck

Lee

[DAVALI]

Whilst you have it apart, you can sort of check the action of the sear engagement by pushing the piston rod into the action without the spring of course!, you also can then check if the spring is too long for the action by measuring the amount of space available when "cocked", measuring the spring wire diameter and multiplying by the number of turns to see if there is any leaway to "Cock" the rifle, if its had a "Generic" spring fitted it possibly needs to be shortened.

Dave

[micky2]

Hi put it back together with out the spring fitted and see if it cocks, if it does then it is more than likey the spring is to long or had a different one fitted which is a wrong one, if not then it could be the cocking arm may be worn. or not quite straight.

[j_potter]

many thanks for all these replies. it's great to have some support when you're not sure what you're doing. I've now taken it apart again and re-assembled it without the springs. it now cocks fine so it looks like it is the springs which wont allow the piston to travel far enough back. there are two springs that don't look damaged or worn in any way. what do I do next ?
many thanks, joe

[DAVALI]

It sounds like you have the correct springs, one should be wound a different way round, i.e. contra-wound!, have you worked out their total compressed length?, this will give you some idea as to how many turns to remove, you should get away with only shortening one but the purist will say remove equal amounts from each, If your not sure how to do this or unable to then I'm sure there's someone near you who will assist,

Dave.

[edbear2]

Hi Joe, the link below regards a Light Pattern but shows the idea;

http://www.network54.com/Forum/67044...ing+dimensions

But essentially the very first job is to check inside the piston to see if someone in the past has put any washers up there to try and increase preload. If not then you need to do the sums as per the above link, ie. available space from piston inside bottom to breech block face.

Next is to work out you spring height so wire dia x number of coils...This should ring alarm bells at once if even close to your initial measurement as although the springs on these compress fairly tightly, they are not normally coilbound.

If you have a pair of opposite wound springs, look closely at the ends for markings like this;

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

The ones shown will be original BSA...if plain then they will be patterns (which have been made since for ever, so may be 100 years old themselves!) The originals twins on 43'' guns from this period are a rounded end oval / flattish wire, not round.


Looks like you are probably into removing a coil or so from at least one spring. This has been covered at great length on this forum so do a search, easy if you have a Dremel / propane torch.



Below is general stuff for anyone else who may have had this problem as a couple of other things can crop up;

CHECK IF IF THE SECONDARY COCKING LINK IS IN GOOD ORDER, AND THE PISTON SLOT HAS NOT BEEN ELONGATED ,


Take note of the red highlighted bit above, I have seen both reshaped / bent / bit at the end damaged arms and bad piston slots over time in repairing these, and have been caught out myself at first as I have had access to spare known good springs / pistons / trigger blocks have swapped them into non cocking guns...and have been scratching my head at why the thing still will not cock even without a spring as both the previous steal a bit of piston travel

Webley MK 3's can also suffer from the secondary cocking arm bending and subsequent loss of piston travel....Usually caused by those muppets who yank on the cocking arms like Gibbons and slam them back...I still see this on occasion when out and about, total lack of mechanical sympathy!...I have even see MK 3's where the MAIN arm is bent as well as the secondary and the twonks yank the thing harder and harder as the secondary arm starts to curve out of shape and the gun fails to latch!

Have a play and report back, It can sometimes be a combination of all the above, but good advice as usual has been given, especially the bit about cocking without a spring

[arbe]

Hi J-Potter. I too had exactly the same problem you describe with my BSA improved model D. The fault was found to be that as described in the last reply of edbear2 where he has highlighted part of his answer in red. There is a long slot in the piston with a half moon shape at each end. One of the half moons was worn out of shape. The cocking lever which pushes on it when loading was slightly worn too resulting its failing to push that last millimetre necessary.
To prove this to myself I Araldited a very small piece of hard plastic to the tip of the cocking arm which took up the slack where it met the half moon shape. It then cocked straight away. Good luck.

[j_potter]

Hi all, many thanks again for all this information. i'am going to have to leave it now for a couple of days as it's the wifes 60th. i'll post again when I've had a chance to try these options. hopefully my last post will be letting you all know what power it's putting out !

[j_potter]

gentlemen, in my youth there was an American television series called 'the twilight zone'. I don't think they ever made an episode about an air rifle but they could easily have used mine. i'am now in a position to state a few 'facts'.

01 if you remove the springs the rifle will cock with a crisp click as the sears engage. it does this every time.

02 if you replace the springs it will not cock although the trigger is pushed back to a position which must be very very close
to the cocking position.

03 following edbears very clear instructions the space between the rear of the piston and the face of the trigger block is
3.46mm measured with a digital Vernier gauge. the available depth in the piston to accommodate the spring is 95.42mm.
3.46 + 95.42 = 98.88mm. lets call it 99mm.

04 there are two springs each with 20 coils. the average coil measures 2.25mm. 40 x 2.25 = 90mm which means that there
is 9mm of 'free space' before the coils would bind on compressing.

I think arbe's suggestion is a good one as it doesn't involve any cutting or filing of the existing metal but I havn't tried it yet.
supposing it works it still doesn't explain why it cocks without the springs but not with. i'd really like a proper engineering explanation before I start chopping things about or should I accept that the world of antique airguns is full of mystique and unexplained things ?

[micky2]

gentlemen, in my youth there was an American television series called 'the twilight zone'. I don't think they ever made an episode about an air rifle but they could easily have used mine. i'am now in a position to state a few 'facts'.

01 if you remove the springs the rifle will cock with a crisp click as the sears engage. it does this every time.

02 if you replace the springs it will not cock although the trigger is pushed back to a position which must be very very close
to the cocking position.

03 following edbears very clear instructions the space between the rear of the piston and the face of the trigger block is
3.46mm measured with a digital Vernier gauge. the available depth in the piston to accommodate the spring is 95.42mm.
3.46 + 95.42 = 98.88mm. lets call it 99mm.

04 there are two springs each with 20 coils. the average coil measures 2.25mm. 40 x 2.25 = 90mm which means that there
is 9mm of 'free space' before the coils would bind on compressing.

I think arbe's suggestion is a good one as it doesn't involve any cutting or filing of the existing metal but I havn't tried it yet.
supposing it works it still doesn't explain why it cocks without the springs but not with. i'd really like a proper engineering explanation before I start chopping things about or should I accept that the world of antique airguns is full of mystique and unexplained things ?

Hi if you have a spring the is shorter than the 2 springs that will fit, see if it will cock with that spring fitted.