BSA Standard Repair Query – which challenges competent airgunsmith

[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 ......

[eyebull]

This may not be relevant at all to your gun, but in the interest of sharing knowledge I had a somewhat similar issue with a BSA supersport built from spares that would not cock. Took a while to figure it out, but in the end it was just oversprung, and the removal of a coil from the mainspring fixed the problem.

[andrewM]

Happily, I have received an email from Protek today that they have fixed the rifle and solved the problem. I am awaiting a full report, which I will then make available here for those who are as keen as I am to discover what was wrong with the rifle.

Many thanks for all the contributions which enabled Protek to get to the bottom of this complex difficulty. I will report back in due course.

[andrewM]

I am now furnishing Protek's diagnosis and solution to the problem; I am a little behind because my email server was down most of yesterday and today.

Many thanks to all those who responded with ideas and suggestions, all of which were passed to Protek. Thank you, also, to ggggr who phoned Protek twice to discuss the matter in person. I owe you a pint or two should we meet.

"Hello Andrew, in the end I replaced the piston that was originally fitted to the rifle. The one you received was either worn at the cocking notch or made with the notch higher up. Comparing it with a post 1929 piston from a working rifle it could be seen that the notch came down further. Neither notch was full diameter of the rod but difference was just about visible and certainly measurable. Still did not work with first piston so I replaced the sear with one from a mark 3 which held side by side showed a higher sear point and fitted. I fitted a tiny spring guide in the trigger/sear spring to prevent it kinking as the hole in the Mark 3 sear is slightly bigger than the one in the bsa trigger. I have seen the little guides in some older post 1918 BSA rifles. There was not one in your rifle as you brought it in. This lack of a spring guide would not have been the cause of it failing. I did of course try various sear springs during working on the rifle.

It now cocks consistently and cleanly. I am NOT prepared to fit a stronger spring as it would over stress the rifle and almost certainly cause deformation of the cocking link which was the first cause of it not cocking, there is now just enough clearance between the link and the piston skirt to prevent the skirt hitting the link on firing with the spring now fitted. A stronger spring may cause the piston head to compress more on firing meaning there is contact with the link on firing and resulting in the link bending or damage to piston at the contact point. This is not a theory I have seen before but with the tolerances in your rather worn rifle I think it is one that is correct. I would be interested to know what others think. Regards, Vic. "

Not all of this is clear to me, as I have never dismantled a springer but I think it will be clear to the technical experts here and I will certainly be interested in further views, as will Vic who, incidentally, will be at Kempton with a table and is worth meeting.

I hope j_potter manages to solve his problem, which seems to come from the same examiner!

[ggggr]

I am now furnishing Protek's diagnosis and solution to the problem; I am a little behind because my email server was down most of yesterday and today.

Many thanks to all those who responded with ideas and suggestions, all of which were passed to Protek. Thank you, also, to ggggr who phoned Protek twice to discuss the matter in person. I owe you a pint or two should we meet.

"Hello Andrew, in the end I replaced the piston that was originally fitted to the rifle. The one you received was either worn at the cocking notch or made with the notch higher up. Comparing it with a post 1929 piston from a working rifle it could be seen that the notch came down further. Neither notch was full diameter of the rod but difference was just about visible and certainly measurable. Still did not work with first piston so I replaced the sear with one from a mark 3 which held side by side showed a higher sear point and fitted. I fitted a tiny spring guide in the trigger/sear spring to prevent it kinking as the hole in the Mark 3 sear is slightly bigger than the one in the bsa trigger. I have seen the little guides in some older post 1918 BSA rifles. There was not one in your rifle as you brought it in. This lack of a spring guide would not have been the cause of it failing. I did of course try various sear springs during working on the rifle.

It now cocks consistently and cleanly. I am NOT prepared to fit a stronger spring as it would over stress the rifle and almost certainly cause deformation of the cocking link which was the first cause of it not cocking, there is now just enough clearance between the link and the piston skirt to prevent the skirt hitting the link on firing with the spring now fitted. A stronger spring may cause the piston head to compress more on firing meaning there is contact with the link on firing and resulting in the link bending or damage to piston at the contact point. This is not a theory I have seen before but with the tolerances in your rather worn rifle I think it is one that is correct. I would be interested to know what others think. Regards, Vic. "

Not all of this is clear to me, as I have never dismantled a springer but I think it will be clear to the technical experts here and I will certainly be interested in further views, as will Vic who, incidentally, will be at Kempton with a table and is worth meeting.

I hope j_potter manages to solve his problem, which seems to come from the same examiner!

I may be being thick here--but would a new Piston Rod http://www.airgunspares.com/store/pr...art-No.-STD13/ cure this or is the problem still with the sear? (given the sear worked in another block???) I think a few of the the tuners and engineers on here can make up piston rods so should be able to sort something out (either making a rod or building up with a decent welding set up and reshaping the notch on the rod)
I would agree with not trying to squeeze any more power out of the gun by fitting a stronger spring. With an old and worn gun, sometimes with a bit less power/ spring they can function well in the less streseed state but that little bit more can shove them over the edge of reliability.

It is interesting to know about the Mk3 sear.
Reading this through, it does seem that is needed reducing to the basics of piston/rod and sear to find the problem, rather than looking at other things.

At least you have a working gun now

[andrewM]

I may be being thick here--but would a new Piston Rod http://www.airgunspares.com/store/pr...art-No.-STD13/ cure this or is the problem still with the sear? (given the sear worked in another block???) I think a few of the the tuners and engineers on here can make up piston rods so should be able to sort something out (either making a rod or building up with a decent welding set up and reshaping the notch on the rod)
I would agree with not trying to squeeze any more power out of the gun by fitting a stronger spring. With an old and worn gun, sometimes with a bit less power/ spring they can function well in the less streseed state but that little bit more can shove them over the edge of reliability.

It is interesting to know about the Mk3 sear.
Reading this through, it does seem that is needed reducing to the basics of piston/rod and sear to find the problem, rather than looking at other things.

At least you have a working gun now

Thanks Ggggr; I put the question to Protek and here is their reply:

"Hello Andrew, a new rod made with a larger cocking notch may well have fixed it - the rod would have had to be properly hardened or it would wear quickly. But fitting a new sear with just a bit more bite as well as the different piston has worked. What has been done is the equivalent of adding more metal where the rifle had worn or been modified in the past. Welding would have achieved the same result but maybe not as durable without proper care and attention. Regards, Vic."