BSA Mercury Mk 4

[Hsing-ee]

Having cleaned, resealed and relubricated this rifle I’ve done a bit of testing..

It’s running at about 10 fpe which should improve as the ‘O’ ring beds in. It’s smooth to cock and fire. The trigger is reasonably crisp and creep free. It seems to be a bit pellet-sensitive but JSBs in 4.52 mm seem to suit it. It definitely has accuracy potential to go less than 15mm at 30 yards.

But it is really hard to shoot consistently. It’s hold-sensitive, has a massively heavy piston and a powerful spring with a lot of preload. It’s a relatively light rifle so you really need to know how to shoot a springer. It would probably be easier in .22, and maybe if it had the long-stroke conversion and a weaker spring.

I could probably get consistent accuracy with it if I practiced for many hours with it. It’s like the BSF zi once had, aesthetically pleasing and lightweight but .. very difficult to shoot. The accuracy potential is there, but I’m just not willing to put the time in when other rifles make it so much easier.

It’s going on the ‘up the road’ pile. I enjoyed the rebuild …

[MartynB]

Having cleaned, resealed and relubricated this rifle I’ve done a bit of testing..

It’s running at about 10 fpe which should improve as the ‘O’ ring beds in. It’s smooth to cock and fire. The trigger is reasonably crisp and creep free. It seems to be a bit pellet-sensitive but JSBs in 4.52 mm seem to suit it. It definitely has accuracy potential to go less than 15mm at 30 yards.

But it is really hard to shoot consistently. It’s hold-sensitive, has a massively heavy piston and a powerful spring with a lot of preload. It’s a relatively light rifle so you really need to know how to shoot a springer. It would probably be easier in .22, and maybe if it had the long-stroke conversion and a weaker spring.

I could probably get consistent accuracy with it if I practiced for many hours with it. It’s like the BSF zi once had, aesthetically pleasing and lightweight but .. very difficult to shoot. The accuracy potential is there, but I’m just not willing to put the time in when other rifles make it so much easier.

It’s going on the ‘up the road’ pile. I enjoyed the rebuild …

I was going suggest trying RWS Hobby's if .22

[Hsing-ee]

I was going suggest trying RWS Hobby's if .22

Just had a squint down the recessed muzzle and it just MIGHT be a crown issue as suggested by Joffy.

[maximus]

How many different pellets have you tried? I spent years messing with my 177 Airsporter S, different springs piston seals etc. Its now shoots very well with falcon accuracy plus which are not to dissimilar in spec to 177 Eley wasps.

[Shed tuner]

the Diana seal conversion will greatly improve it's firing manners.
rod a pellet thru the barrel to see how cleanly it emerges from the crown.

[Hsing-ee]

the Diana seal conversion will greatly improve it's firing manners.
rod a pellet thru the barrel to see how cleanly it emerges from the crown.

I do have another piston I could try that on...

The pellet appears to have deeper rifling grooves on one side than the other. That is messed up right? And the answer is some lapping paste and a brass round headed screw isn't it? Just difficult to do this with the countersunk bore...

[maximus]

When I pushed pellets down my Airsporter S barrel it felt like they hardly touched the sides. I suppose pushing through is not representative of having a load of high pressure air up the pellets chuff though is it?

[rapidresponse1]

hope you get it sorted bud

[TonyL]

Looking back at the original post, there may be nothing sinister going on here? Maybe just the hold sensitivity initially described? Might improve slightly as it beds in more and as Al gets used to it, if he's willing to give it the time?

P.S....A little more weight might help, too. More weight all-round will help, but particularly some more weight up front and at the butt?

[maximus]

What spring have you got in it?

[Hsing-ee]

[QUOTE=TonyL;8291809]Looking back at the original post, there may be nothing sinister going on here? Maybe just the hold sensitivity initially described? Might improve slightly as it beds in more and as Al gets used to it, if he's willing to give it the time?

P.S....A little more weight might help, too. More weight all-round will help, but particularly some more weight up front and at the butt?[/QUOTE

I like to use 6 yard air-rifle targets with a small neon dot sticker on the X ring centre. The scope didn’t bounce out of the black at 30 yards. It’s not that jumpy.

Anyway after considering Jon’s advice and seeing the pellet was not marked evenly all the way round, I had a gentle go at the crown with a tool I won’t mention. It felt like there was a lip or ridge at the muzzle, a few rotations of the tool and this sensation disappeared. I tried again with a fresh pellet pushed through and the rifling marks were present all the way found and nice and deep. I’m going to polish the new chamfer and then test it out, although that’ll have to wait til the weekend. Hopefully I haven’t made things worse.. I think there was a tiny lip and the pellets were being clipped by it.. the JSBs were the thinnest and soft pellets so that’s probably why they were better in terms of accuracy…

[TonyL]

Excellent stuff. I hope that's done the trick. Do report back.