BSA Standard Repair Query – which challenges competent airgunsmith

[andrewM]

We have a problem with a T Model Bsa standard (1930s) Basically, the trigger is firing of its own accord: as soon as it is cocked, it releases itself and will not hold.

I have given it to Protek to repair but they are in difficulty. They report:

“I have tried 3 pistons now, 3 cocking links and 2 trigger mechanisms. Your rifle will only work with a different trigger block (regardless of trigger components) so the problem is with the existing trigger block - but not sure how to sort it out or even why it won't work. It nearly does but not quite. I look at the rifle and get depressed and frustrated about it. Your trigger block will not work on the 2 other rifles I have tried it on either.” Unquote.

A new trigger block cannot be used because of the different levels of finish. If the mechanism could be revolved one further turn, it is expected the mechanism would operate but this would mean that the holes for the screws became inoperative and out of line.

3 different sears have been tried but none of them worked in this trigger block. But the sear from this rifle worked in another rifle. It is possible the rifle’s trigger block is making the mechanism bind up – one possible theory.
We have tried different pistons so we can discount this.

Can anyone help?! Protek would like to receive suggestions - as would I!

Many thanks!
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[andrewM]

That is a very helpful answer, which I have copied to Protek. I cannot answer your question but no doubt Protek will. We knew that a boffin would assist with this most technical of queries - the sort that one might answer in an exam! Probably, we will receive further views and, ultimately, we will report back on the result.

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[andrewM]

I think you are on to something, Grrrr! Here is Protek's reply:

"Hello Andrew, he might be on to something re the stock bolt. The stock has obviously been off the trigger block and when reassembled they may have left a spring washer off resulting in the stock bolt going in too far when fully tightened. I had not considered it but is a good call by GGGR and I will look at it at the weekend. I have some of the correct spring washers as well so heres hoping, regards, Vic." Unquote.

We will have to see what he now comes up with and I shall let you know.

Meanwhile, this all goes to show what a wonderful resource this site is for collectors; the pool of knowledge and expertise is enormous.

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[andrewM]

Is there any news on this yet?

Nothing as yet; he might not have had a moment to play with it. I am most curious to find out if you have cracked the problem! Shall revert as soon as I have something.

[El Garro]

If you think the sear would engage if the trigger block could be turned another thread, would it be worth carefully filing the sear notch on the piston rod to make up the difference ?

[andrewM]

Hi Ggggr!

Just had this in from Protek:

"No luck with BSa. Removed stock from trigger block - no difference. Filed inside of sear a little - made no difference. Have bought in piston and sear and going to ask a mate to put a little metal on to piston notch and top of sear so that the bite of the sear on to piston will improve. If it does and the rifle cocks consistently it may only be suitable for use with the lightest spring that will allow the pellet to exit barrel."

What do you think? This is all most odd and a real challenge, it seems.

El Garro, I will raise your point with Protek. Thanks for that.

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