Mercury Spring question.

[GATMAN]

I have a BSA Mercury Mk I .22 which is shooting at 8 ft/lb.

I have dismantled the rifle and have a spring handy for HW 35/ 80 which will fit. It is rather long I feel at 32 coils and needs cutting back to suit. I have already turned up a nice spring guide to suit the Merc. and the HW spring.

How many coils should a Mercury spring have ?

Before you ask, the spring removed was non standard and way too short as I was able to remove and re-fit by hand without the spring compressor I have.

Also I have a chronograph to make sure it stays under the 12ft/lb limit

Ideally, I am looking for 11 + ft/lb and smoothness.

Thanks in advance for advice guys.

Paul.

[Paddy_SP]

I don't think it will help you to use the same number of coils as the stock Mercury unless you can be absolutley sure that the wire thickness and winding pitch were the same. Personally, I think I'd cut the spring so that it had what seemed to be about the right amount of preload, and see what it chrono'd at...

[GATMAN]

I don't think it will help you to use the same number of coils as the stock Mercury unless you can be absolutley sure that the wire thickness and winding pitch were the same. Personally, I think I'd cut the spring so that it had what seemed to be about the right amount of preload, and see what it chrono'd at...

I may be limited in spring length by how difficult it is to get the trigger block back on. The curved portion certainly looks good, but I think it may well be difficult to keep it central in the compressor when it comes to reassembly

As a matter of interest, does anyone know what the spec. (wire thickness and no. of coils) of the standard spring was (35 years ago !)

Paul.

[Shed tuner]

What Paddy said, trial and error mate...

[Shed tuner]

Incidentally, with a shortish stroke and a heavy piston, I wonder if lightening the piston might reduce the recoil on these guns ?

[smith.c]

spring I replaced in my mercury id 13.90 -wire 3.26 -length 235 -coils 33
made by pok on bbs I believe that he is not able to make any more springs till new year
As for curved trigger ass on bsa I made a fitted wooden block 2 x 3 with center cut out to shape so my compressor is square on end
colin

[Shed tuner]

As for curved trigger ass on bsa I made a fitted wooden block 2 x 3 with center cut out to shape so my compressor is square on end
colin

Did.. made in two halves, bolt together

[mr smith]

Was able to change the spring on a mercury by hand.The new one was a maccari one don't know if that would make any difference.

[GATMAN]

Update

Today I installed the HW spring. I managed to fit the full length 32 coils and found I could get the end block screwed back on by hand, pushing against the floor - much easier than I had imagined..

The cocking effort is now heavier but still smooth.

Strange thing is, over the chrono, the gun is only up to 8.5 ft/lb

I'm using AA Fields 5.52 as the latest Wasps 5.6's I bought are total crap.

I'm thinking I may have a sealing problem with the new Piston head I fitted.

I wonder if it's possible to fit an HW piston washer to the Mercury piston (I can easily machine the piston head at work) and I've got a spare HW 35 washer. Has anyone tried this ?

There could be clearance problems with the cocking arm / piston slot relationship if I do this though, due to the extra swept volume the HW washer will give me, as I wont need the standard buffer behind the head.

I'll probably need to make a piston weight also to compensate for the removal of the aluminium piston head.

Oh what fun !

Springers....I love them

Paul.