BSA double sear project, latest progress, new questions.

[stevegv8]

An update at last on this project, I have started a new thread as it has been a few weeks since it dried up, link to original below if a catch up is needed.

http://www.airgunbbs.com/showthread....rigger-problem

To recap I needed a piston and double sear unit for this project as the gun came with a botched piston rod and double sear.

The end notch on the rod had been removed and the front lobe(?) of the sear had been cut right down no doubt to become single sear but was the one that should have been left alone hence no latching as no surfaces mate up.

I searched the normal known parts outlets, and this forum for the parts and a sear showed up on here.
I had the chance to borrow a piston of a double sear type for measuring how to cut a new rod to fit to my piston.
The borrowed piston was from a shorter cylinder gun but the rod pattern was all we needed. Careful measurements taken to work out where the rod notches need to be for latching at the correct point of full cocking.

Then it turned out the new sear was also worn and filed such that it would not be able to latch on the new rod and the answer was to build up the profile on each sear with weld, re shape to match the rod notches and case hardened afterwards.

New pics show the parts & trial assembly

https://imgur.com/gallery/tsBo4R7

Next concerns are:
When setting the trigger guard screws nice and tight the trigger locks up but is Ok if they are not made tight??

It lacks power so original spring and leather washer in question. Power is such that it won't fire Ely Wasps but will fire (at low velocity) Milbro Caledonian.
The Wasps are tight through the loading tap (when trialled out on the bench) at 5.56 & the Caledonians are not so tight at 5.55, I think I recall wasps are good for BSA's but maybe not early guns? Especially if power is low.
So I have a working gun at this pint but will knock over feathers more than cans

[Lakey]

Thanks for the update. An interesting thread, and I wish you the best of luck getting this rifle back up to full health.

Lakey

[DCL_dave]

An update at last on this project, I have started a new thread as it has been a few weeks since it dried up, link to original below if a catch up is needed.

http://www.airgunbbs.com/showthread....rigger-problem

To recap I needed a piston and double sear unit for this project as the gun came with a botched piston rod and double sear.

The end notch on the rod had been removed and the front lobe(?) of the sear had been cut right down no doubt to become single sear but was the one that should have been left alone hence no latching as no surfaces mate up.

I searched the normal known parts outlets, and this forum for the parts and a sear showed up on here.
I had the chance to borrow a piston of a double sear type for measuring how to cut a new rod to fit to my piston.
The borrowed piston was from a shorter cylinder gun but the rod pattern was all we needed. Careful measurements taken to work out where the rod notches need to be for latching at the correct point of full cocking.

Then it turned out the new sear was also worn and filed such that it would not be able to latch on the new rod and the answer was to build up the profile on each sear with weld, re shape to match the rod notches and case hardened afterwards.

New pics show the parts & trial assembly

https://imgur.com/gallery/tsBo4R7

Next concerns are:
When setting the trigger guard screws nice and tight the trigger locks up but is Ok if they are not made tight??

It lacks power so original spring and leather washer in question. Power is such that it won't fire Ely Wasps but will fire (at low velocity) Milbro Caledonian.
The Wasps are tight through the loading tap (when trialled out on the bench) at 5.56 & the Caledonians are not so tight at 5.55, I think I recall wasps are good for BSA's but maybe not early guns? Especially if power is low.
So I have a working gun at this pint but will knock over feathers more than cans

Hi Steve,

I may have a 1 1/8" (28mm) BSA piston seal knocking about somewhere, will look a bit later and let you know but if I have you can have it FOC if it's any good to you.

[stevegv8]

Hi Steve,

I may have a 1 1/8" (28mm) BSA piston seal knocking about somewhere, will look a bit later and let you know but if I have you can have it FOC if it's any good to you.

That'll be nice, I'll wait and see if you find it, thanks

[DCL_dave]

Hi Steve,

Sorry for delay. Right, I found a 28mm BSA cup seal/washer looks a little rough but your welcome to it, or give me a few days and I'll knock some up...(I thought I had some in the box but I have given a few away on t'other side recently and now seem to have ran out...)

Same as for t'other chap though, if you want some bits of leather to make one yourself your welcome to some.

[DCL_dave]

PM sent

[silva]

An update at last on this project, I have started a new thread as it has been a few weeks since it dried up, link to original below if a catch up is needed.

http://www.airgunbbs.com/showthread....rigger-problem

To recap I needed a piston and double sear unit for this project as the gun came with a botched piston rod and double sear.

The end notch on the rod had been removed and the front lobe(?) of the sear had been cut right down no doubt to become single sear but was the one that should have been left alone hence no latching as no surfaces mate up.

I searched the normal known parts outlets, and this forum for the parts and a sear showed up on here.
I had the chance to borrow a piston of a double sear type for measuring how to cut a new rod to fit to my piston.
The borrowed piston was from a shorter cylinder gun but the rod pattern was all we needed. Careful measurements taken to work out where the rod notches need to be for latching at the correct point of full cocking.

Then it turned out the new sear was also worn and filed such that it would not be able to latch on the new rod and the answer was to build up the profile on each sear with weld, re shape to match the rod notches and case hardened afterwards.

New pics show the parts & trial assembly

https://imgur.com/gallery/tsBo4R7

Next concerns are:
When setting the trigger guard screws nice and tight the trigger locks up but is Ok if they are not made tight??

It lacks power so original spring and leather washer in question. Power is such that it won't fire Ely Wasps but will fire (at low velocity) Milbro Caledonian.
The Wasps are tight through the loading tap (when trialled out on the bench) at 5.56 & the Caledonians are not so tight at 5.55, I think I recall wasps are good for BSA's but maybe not early guns? Especially if power is low.
So I have a working gun at this pint but will knock over feathers more than cans

I have had Imp Mod D’s with a loop of ancient plumbers twine in the end of the block. Which was obviously a period or even factory fix. This may cure the sloppy fit of the block into the cylinder which may be the source of your trigger guard screw problems.

[stevegv8]

I have had Imp Mod D’s with a loop of ancient plumbers twine in the end of the block. Which was obviously a period or even factory fix. This may cure the sloppy fit of the block into the cylinder which may be the source of your trigger guard screw problems.

I don't have a sloppy fit as such although when tight the block does go a fraction past the "home" position, backed off a fraction so the screws will thread it's all fine unless I set them as tight as the ought to be. ??

[edbear2]

I don't have a sloppy fit as such although when tight the block does go a fraction past the "home" position, backed off a fraction so the screws will thread it's all fine unless I set them as tight as the ought to be. ??

Really daft question, but have you done them up with the block off and looked down the spring guide to make sure they are not a fraction too long ?.....these screws can strip and can be replaced with 2BA screws, if done well this is hard to spot and obviously the replacements can be longer.

If you measure them and post on here people could tell you if the correct length.

ATB, ED

[stevegv8]

Really daft question, but have you done them up with the block off and looked down the spring guide to make sure they are not a fraction too long ?.....these screws can strip and can be replaced with 2BA screws, if done well this is hard to spot and obviously the replacements can be longer.

If you measure them and post on here people could tell you if the correct length.

ATB, ED

I will look into that, also update on my post above, the block actually threads in by just less than a quarter turn past the central position when tight so is backed off some amount for fitting trigger guard and screws which then lock the trigger when they are tight, so will look into their length.

[edbear2]

I will look into that, also update on my post above, the block actually threads in by just less than a quarter turn past the central position when tight so is backed off some amount for fitting trigger guard and screws which then lock the trigger when they are tight, so will look into their length.

Hi Steve,

It's quite common for the blocks to rotate past the lining up point, 1/4 turn seems quite a lot but have seen similar.

ATB, Ed

[stevegv8]

The latest news on this project.
I had dry assembled this project (well not dry but for test purposes) and found the trigger sticking if the trigger block screws were screwed down tight.
It was suggested they maybe too long and did look like good aftermarket copies (clean and not damaged) so I ground a threads length off but still the same? Additionally though it wouldn't latch up, big dilemma after the whole project was about fixing the double sear.
Thinking back it latched with the screws loose so I put them in with no trigger guard at all too see if it was worse thinking I could check if more needed to come off the screw length.
However the trigger didn't stick at all! so now it seemed the fault was only with the guard tightly fitted.

Looking closely at the trigger blade I could now spot that it bottomed out onto the guard and this meant when tight the sears could not reach upto the correct point of the rod which was extending a fraction short, with it loose they could meet but the trigger was sticking and no guard it worked fine.

So some carefull dressing of the contact point on the trigger lowest point where it wouldn't be visible and a bit of cold blue after and the gun works a treat at last.
I set the trigger with short pull then backed off a bit so as not to fire if jolted, a lighter trigger spring and feels fairly good finally.

New leather washer supplied by DCL_dave fitted to it and all done I hope.

Can't do a detailed chrono as the Caledonian pellets I use I don't know the weight of but wild guessing .85 grams it shows only 6 ft lbs on it's first 5 virgin shots, needs to bed in no doubt but wasn't looking for power I just wanted it to work and it's still on it's old spring after all which I might replace but happy for now.

[DCL_dave]

Hi Steve,

This site, although not updated now...is handy for pellet weights and the power calculator https://extorian.co.uk/shooting/pellets.html

[edbear2]

If it is a 43 inch length gun, they can go 725 FPS but most are mid/high 600's I have found if that helps......these figures with Wasps and a tad more with Meisterkugeln etc. type match pellets which they often like, Hobby being a good choice quite often.

ATB, ED

[stevegv8]

Nice useful link from DCL_dave 2 posts above, thanks.

My guess was quite good, out by .01 gram. So reset test and get 445.5 fps 6.138 ft/lbs short of fitting a spring that's about it, I collect & rarely get to plink sadly so don't really need more power, just wanted it working.
I think out of interest I may eventually do a spring one day subject to sourcing the correct item, best places to enquire?