My Mercury Ratting Rig

[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. :-

image.jpg

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...

[T 20]

It'll be a laugh if this lot don't work.

And --- it's complete crap.

After dieseling a couple of times the trigger blade snapped in half, which I've had happen before with the same trigger unit on an Airsporter S.
Once the gun settled down it gave a consistent 525fps over the chrono with Superdomes with 106mm of compressed Spring height.
So I took it apart and stuffed in another four preload washers in, cutting the compressed Spring height down to 98mm --- over the chrono it gave a very consistent 559fps with Superdomes for an earth shattering 10ftlbs and it was getting a bit slammy.

Now I don't think this low power and slam is down to the action --- I think it's down to the barrel.
Any type of pellet I have easily drops into the breech, some fall 3-4mm into the barrel as they're way too small for the rifling.
Strangely I didn't have this problem with the Mercury S I serviced the other week so now I think the low power could be down to the pellets setting off too early in the firing cycle.
I'll have a look through my spares in the morning and see if I've got a tighter barrel, if not I'll have to shelve the gun until a later 5.5mm barrel shows up in sales.
I was going to open the transfer port up to 3.2mm but with the lost volume in the barrel it could make things worse so I'll swap the barrel before modifying anything else.





All the best Mick

[evert]

Could it be a leaking/porous breech?
I had to screw the forks out of my mercury tube and put them back in with new thread locking glue to get it working properly.

[T 20]

Could it be a leaking/porous breech?
I had to screw the forks out of my mercury tube and put them back in with new thread locking glue to get it working properly.

I don't think it's porous, but that gives me an idea, Evert.

I still have that weird hemispherical chamber in the front face of the cylinder, if I unscrewed the forks I could lathe the front face flat, or MIG it up and then machine it flat --- I take it that they're Loctited in ?

Looking at the barrel again tonight, even FTT pellets drop into the barrel, but these were so tight in the Original 35 barrel that I gave up trying to use them.

I have a couple of .22" Meteor MK1 and MK2 barrels kicking about somewhere, I'll try some pellets in them tomorrow.



All the best Mick.

[TonyL]

Lots of areas for improvement then, Mick.

As you say, you have a good few areas of potential there. If everything seemed okay but the results just weren't coming, it would be much more confounding. I hope you find a barrel easily to hand in your stash.

[evert]

I still have that weird hemispherical chamber in the front face of the cylinder, if I unscrewed the forks I could lathe the front face flat, or MIG it up and then machine it flat --- I take it that they're Loctited in ?

Yes, there was some kind of glue, mine needed some heat before it could be unscrewed.

[T 20]

Lots of areas for improvement then, Mick.

As you say, you have a good few areas of potential there. If everything seemed okay but the results just weren't coming, it would be much more confounding. I hope you find a barrel easily to hand in your stash.

Every 5.6mm BSA barrel I tried was the same, Tone --- Superdomes and Hobbies just fell in and settled 3-4mm down the bore.

Then I realised I had a box of these that I've never tried. :-


image.jpg



Proper 5.6mm pellets --- result, 11.95ftlbs.

But, and it's a big but, the gun still feels a bit too slammy for my liking and I think this is now down to the hemispherical cutout in the front of the cylinder --- I reckon there's about three times more lost volume in that hemisphere than in the transfer port.

I did take an impression of the hemisphere using Blu Tac and cling film on the front of an old piston but I forgot to photograph it or measure it --- I should really have cast it in P38 body filler as a pattern for the piston.

Ah well, I'll put it to one side for now and get on with something else while I think about it.




All the best Mick

[T 20]

Yes, there was some kind of glue, mine needed some heat before it could be unscrewed.

Cheers Evert.

I shall have a ponder on this lot now --- whilst looking in my spares this morning for BSA Meteor barrels I found a couple of Oldschool HW85k actions and a HW95 stock which would probably make a better gun than Merc ever will without any machining.



All the best Mick

[evert]

Cheers Evert.

I shall have a ponder on this lot now --- whilst looking in my spares this morning for BSA Meteor barrels I found a couple of Oldschool HW85k actions and a HW95 stock which would probably make a better gun than Merc ever will without any machining.



All the best Mick

But you have done a lot work, and gotten good results so far, why not just do the last finishing step on the Mercury?
Besides, the 95/85 has a too long stroke for sub FAC, so you'll need to make a new piston for that gun too....

[T 20]

Yes, there was some kind of glue, mine needed some heat before it could be unscrewed.

Hi Evert.

Out of interest was your cylinder end flat or did yours have a hemispherical recess in it ?

I'm thinking mine could be a machining cock up at the factory.

But you have done a lot work, and gotten good results so far, why not just do the last finishing step on the Mercury?
Besides, the 95/85 has a too long stroke for sub FAC, so you'll need to make a new piston for that gun too....

Go on then --- I'll get the gas axe out.

I originally bought this Mercury as bits as my other two break barrels (Webley Hawk 2 and HW35) weren't up to the job of dealing with my neighbour's rat problem.
My ownership of this Merc is also tied in with me joining the BBS to get a new cylinder for my HW35 so I suppose I should carry on with it.




All the best Mick

[TonyL]

It would be very useful if accuracy testing with the Marksman pellets was satisfactory, Mick, although I wouldn't be holding my breath on that one......Depending on range, though, they might just be viable? Remember Rod Linton's pellet test series back in the early days of AGW and the stand-out performance of the .177 Mercury with the Marksman pellets?. But one or two did later point out on here that we didn't get the truth, the whole truth...

Good luck with the cylinder end explorations.

Any joy on the quest for a later, tighter barrel?

I wonder how many people may have switched to a .177 barrel in recent years for pellet compatibility and availability reasons? Yes, there'd be a drop in efficiency, but might be worthy of a look? Although ratting might be the main time that I'd prefer that extra (perceived?) reassurance of the .22.. But I don't doubt that the .177 would prove just as effective and I'm sure many on here might use the smaller calibre on rats to good effect?

[crowbar]

I would like to see it in bits, perhaps the hemisphere is some home tuning and not factory and as I have never owned
a Mercury I know nothing I thought they would be brazed.If you were not playing with the Mercury you would have to
be doing some work so it's a win win situation for you Mick and us students.

Cheers Crowbar

[evert]

Hi Evert.

Out of interest was your cylinder end flat or did yours have a hemispherical recess in it ?

I'm thinking mine could be a machining cock up at the factory.

No recess, I've put up a picture here:
https://www.airgunbbs.com/showthread...s-wanted/page4

[Shed tuner]

No recess, I've put up a picture here:
https://www.airgunbbs.com/showthread...s-wanted/page4

that looks way too easy to remove for Mick to resist...