My Mercury Ratting Rig

[T 20]

I don't understand.

I have in front of me a Mk4 piston and trigger block,the piston rod passes through the centre of the block and chamfer
on the end sets the sear and it click into the bent. The piston skirt does not touch the trigger block (it has clearance)
and I cannot see a reason for it to do so .

Cheers for that --- you've made me take another look at it and you're right.

The trigger on this gun is what you get on MK6 Airsporter and though the piston skirt comes very close to hitting the back block threads there is indeed a 5 thou" clearance between them.
My initial assumption was that BSA had built this in as a safety device so that once the trigger was set you couldn't force the latch rod further into the back block as the piston tail acted as a positive stop.

I've actually been comparing the various BSA trigger units I have wondering what to use on this gun. :-

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At first I was going to use an Airsporter MK2 unit but it's a false two stage unit with very few benefits, so now I'm leaning towards using the MK6 Airsporter unit with the MK4 Airsporter over travel screw.



All the best Mick

[TonyL]

Lovely work and a mighty fine looking piston there, Mick.

Come on, admit it. You love making these!

[Shed tuner]

a very pretty piston. Now just machine that o-ring crap off the end and stick on a d28 seal and you'll be golden

[T 20]

a very pretty piston. Now just machine that o-ring crap off the end and stick on a d28 seal and you'll be golden

If the latch rod had been longer so that I didn't have to weld the top hat in just where the seal arbor would have been I may have considered using one, Jon.

More importantly though, a 28mm Diana seal is £12.50 and O rings cost me about 20 pence each.

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All the best Mick

[junglie]

If the latch rod had been longer so that I didn't have to weld the top hat in just where the seal arbor would have been I may have considered using one, Jon.

More importantly though, a 28mm Diana seal is £12.50 and O rings cost me about 20 pence each.

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All the best Mick

Lol love the cheeky frankie pic, good work on that piston . will be interesting to see how it shoots, think you made the right decision with the later trigger btw.

[T 20]

think you made the right decision with the later trigger btw.

I can live with the trigger unit shown as it has sear engagement and Spring pressure adjustment screws, the only thing I'd like to add is an over travel adjustment screw.

So I'm going to drill and tap the casing for one along this line. :-

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The screw will be loctited in because once the over travel is set it can remain set for life.




All the best Mick

[Shed tuner]

I get you now Mick. still reckon it'll be better with a longer spring and more spring room though, but really nice work, it's finally getting some love...