BSA Standard Repair Query – which challenges competent airgunsmith

[andrewM]

Thanks Ggggr! You are not the only one lying awake, grappling with this problem. So is Vic, the good airgunsmith at Protek, and he is no amateur at such things. I gather you very kindly spoke to him earlier today and these are his latest comments, some of which he forgot to convey to you at the time.

"Hello Andrew. Have spoken with GGrrr today. He has given me a couple of ideas to play with. But forgot to tell him the trigger group now fitted came from a good working rifle so problem of trigger/sear/ trigger spring interplay can be discounted. - and the components taken from your rifle work in another rifles trigger block. Have not however tried different pivot screws for components which is something I will try. Also will look at inside walls of block to ensure free movement. Interestingly I also came up with the idea of a fractionally misplaced sear pivot hole which over time with wear and the considerable polishing out that your rifle has had could have caused the failure to cock now experienced. I too have laid in bed pondering it. Usually substitution of all parts would sort it out even if not absolutely certain which specific part was at fault - or most at fault as all parts would have worn equally. Not too much in workshop this weekend so will look at iot once more. Just have to remember to put on the heating a couple of hours before I start, regards, Vic." Unquote.

It seems we are discounting the possible causes, one by one - and barking up a few rare trees at the same time! I am fascinated to know what could be causing the problem.

Rgds
A

[Phil Russell]

OK ... I am coming into this a little 'blind' and you may well have tried / looked at these points; so please excuse me if I am repeating things or suggestions are a load of rubbish:
Have you tried taking detailed measurements of all components to see if and where differences are between working and non working combinations?
Would it help to carefully scribe where triggers lie (i.e. scribe a line on the trigger blade) in the different blocks to look for differences in trigger angle, position etc... are trigger pivot holes in exactly the same position for all blocks? Are trigger - sear angles the same when trigger is assembled in different blocks? If the trigger does not hold on the sear under the spring force then clearly it is slipping so my primitive thought is that the contact angle is not correct, due either to worn angles on the trigger or piston ... again maybe a positional thing. I guess the trigger spring is not binding and restricting trigger movement? I assume trigger pivot is a snug fit and that the piston rod is central and not wobbly?
I am looking forward to hearing of the solution ....
Cheers, Phil

[andrewM]

Thanks Phil!

I will certainly put that into the pot by raising it with Protek.

[lightning22]

Feel free to shoot me down in flames, but would it be possible to rule in a defect, rather than trying to rule one out?

Take a known good gun and swap in the individual components or combinations of components to replicate the failure.

[andrewM]

Protek has asked me to ask if anyone has a spare trigger block for this Standard BSA (T model)?

Lightning22, thank you for your suggestion. I think the parts are well used so, I suspect, the problem might be one of wear. If it was defective, I think it would have been returned to the factory shortly after purchase. I will, of course, put your suggestion to Protek.

I suspect we have the best BSA minds in the world following this thread!

A

[j_potter]

Hi Andrew, i had exactly this problem with an improved model b. The thread is on here under 'improved model b'. It brought me to sobs and i still haven't fixed it. The rifle has lain untouched in the cabinet ever since. I discovered that if i araldited a sliver of brass onto the mating face of the cocking arm it would cock with no problem. This is only adding about 1mm if that. This solution doesn't stay in place very long, neither does it answer the question of why it's not working. Beleive me i have stripped it down dozens of times, followed all the very excellent suggestions on here and do understand the mechanism as i am a retired engineer. I'am thinking now i may get a blob of braze put on the cocking arm face which i can file back to a good profile but i really get what you're going through !!!!!
joe

[andrewM]

Hi Joe! Well, on the one hand I was glad to discover I am not alone in this but was most dejected to read that you had not cracked the problem.

I will send this link to Protek as, probably, we are in the same boat. Strange we should be afflicted and that this problem appears not to occur elsewhere, with similar BSAs. But, as you ask, why the heck is it not working? That is the biggest mystery and if it could be solved, the problem could be addressed.

[j_potter]

Well you see Andrew, there are some people out there who want to see some very very cheap BSA's put up for sale ......