Sunday, 30 June 2013

BSA Mercury, The Final Stages

For now.........

Sweet looking air rifle

When last i wrote a blog i had just finished fixing up the BSA Mercury, and left off with popping in the breech seal. However i realised i had forgotten to order one, just missed it out on my order from J Knibbs. So in goes another order for a Titan XS mainspring for the Weihrauch HW35, a flip up red filter for my gun lamp, and two generic BSA breech seals, I got two as i have a BSA Meteor which would benefit from a new one as well.

 When i gave the original Mercury breech seal a close inspection i could see why it needed replacing, one half of it looked liked it had been filed flat so one side was flush with the breech face and the other side protruded a smidgen to where it should seal. 

Worn old breech seal

When i placed a cigarette paper over the breech to see if any air escaped when fired, it didn't just move it, it shot into the air, and that was with me gently holding the paper to the sides of the breech with my fingers.

Ready to replace

The generic breech seals are made from a firm rubber and are white, where as the original is a black harder harder material, but that may be because it has aged and hardened. 

Two new breech seals, i have a Meteor as well.

It's a folded over circular seal with a small slit on the inner fold, and the fold is the side of the seal that faces the outer side of the breech. The old breech seal had to be prised out and as it was so old it came out in small pieces and crumbs, most definately well past it's sell by date.

Oh crumbs!

Though once removed and cleaned the new seal just slipped in easily and straight away i could tell the differance between the old worn seal and the new one, standing just past flush from the breech face and making a perfect seal around the transfer port. 

New breech seal fitted

Cocking the rifle and loading the pellet then taking the shot i could hear the pellet hit the back stop with a lot more force than it had done before. Though i would like to point out that according to a very well known and experienced airgun tinkerer (known to some as T20) reckons that most Wiehrauch breach seals would fit even better to Meteor's, Airsporter's, Mercury's, et al, and give you an extra 1/2 ft/lb as they are made from tougher stuff and are a tad longer. Anyway read his blog 'Air Gun Tech' and you can see for yourself that him and his buddies know their minerals, it all makes sense to me, sort of.

I also made an order to Uttings for a 6x40 AO Nikko Stirling scope and a set of Accushot high profile off set mounts, the mounts arrived but i would have to wait another week or so for the scope as they were out of stock.

Lots of bit's that come with the scopemounts

Scope mounts in the box

I have discovered that after buying loads of economy scopes in the past that it's best to spend a little bit more, though you don't have to break the bank doing this. 6x40 is a good hunting magnification and Adjustable Objective is pretty handy for guaging the distance of your target, and being a little short sighted i can use a scope with AO with my glasses on. However they didn't have any in stock several weeks later, so i reordered a 3-9x40 AO Nikko Sterling and i can just leave it on x6 mag for hunting

Ready to fit the scope

The one piece off set mounts are crucial for BSA Mercury's and any other BSA with the curved trigger unit, as the scope rails are set to far forward for most people to use comfortably with normal mounts. In this case i  mounted an AGS 3-9x40 scope and with the off set facing backwards found it sat just perfectly for my head an eye to line up, two hex bolts clamp the mounts to the scope rails and two smaller hex scope stops screw down to add extra support on the top or the piston cylinder. The Accushot mount came with three allen keys and one spare hex bolt in each size, this was handy as i had a one piece mount with a striped hex head so i popped it in there. The hex head was a little thicker than the others but it does the job fine, and now i have a spare one piece mount for one of my other springers.

Out in the back garden i sat down at 27 yards from my target and trap and took some test shots with .22 Eley Wasps No2's, The scope was fairly close to the POI but the shots were stringing vertically and some went left or right which showed me this rifle would need at least half a tin of pellets to settle down and a very gentle hold, though when i tried some .22 RWS Superdomes i found the grouping was a hell of a lot better but still not upto anywhere good enough for hunting. Most Super domes fitted snuggly into the breech though some were looser and deep seated themselves. However i could feel the wasp's click in snuggly, but they can be seen by eye that they all differ or are slightly deformed in some cases, and would explain why I found this a little odd as old BSA barrels are 5.6 mm and Wasp No 2's are made for this and they just did not perform that well, where as the super domes that fitted deeply where falling into roughly 2 inch groups which was without a doubt an improvement.

With the new main spring and lube this rifle slams the piston home with force but there is no buzz or twang which is a bonus, but for a smoother lock cycle it is in need of a top hat and a slip washer and 3 or 4 coils removing. I feel this air rifle is now performing close to if not a little above factory specks, but give it a bit of running in to settle the spring in and short stroke the piston and its going to be a corker of an air rifle which is not so hold sensetive.

I mean, i shoot at a dot on a piece of paper and my shots appear to go all over the place, but if i place a few bits of 1 x 2 inch wood on the shelf in front of my back stop and i miss one every 5 shots. So it seems i can hit an inch size object better than i can group an inch circle on paper, and that's at different ranges to boot. Now that's all well and good out in a field of rabbits where i originally learn't to shoot well, but i have to garrentee i can do that with whatever air rifle i am using at the time in order to make a clean kill. Most of my air rifles will allow me to do that out to 45 yards in some cases, but with this rifle as it is now i wouldn't like to take the chance, even at 15 yards.

 It would appear that i still have a lot of work to do on this lovely little Mercury, and as this blog is all about my learning curve with working on air rifle dynamics and the improving of my knowledge of said objects. Then it would stand to reason that i will be squeezing a few more blogs off this gun.


Wing Commander, Sir Nigel Tetlington-Smythe.