Airsporter RB2 tune

[Shed tuner]

The thing is, what other BSA would of had that diameter of piston with a central rod? I can't think of any.

me neither, but it could be from a completely different gun. IIRC they are 29mm bore, like the supersport (I know these don't have a central rod). Didn't webley also use this diameter ?

[Oddbob08]

me neither, but it could be from a completely different gun. IIRC they are 29mm bore, like the supersport (I know these don't have a central rod). Didn't webley also use this diameter ?

The piston seal fits in the same way as the Superxxx range, the Webleys were the other way round, ie; Bsa have female pistons, Webley are male. Also, all the modern Webleys (from Hawk/Vulcan onwards) have a slot on the bottom of the piston for the sear to engage with, not a rod.

I've just bought an HW77 compression chamber, maybe I'll beat Shed tuner to the sliding breach conversion. Or it may go in my Eclipse.......

[Shed tuner]

I've just bought an HW77 compression chamber, maybe I'll beat Shed tuner to the sliding breach conversion. Or it may go in my Eclipse.......

quite likely, as I'm about 5,000 miles away from my garage at the moment, keeping away from Covid lockdowns.
Besides my health and sanity, and much nicer weather, another plus is I get to play with my 20 FP pro Elite after a few years break - what a gun

[Oddbob08]

quite likely, as I'm about 5,000 miles away from my garage at the moment, keeping away from Covid lockdowns.
Besides my health and sanity, and much nicer weather, another plus is I get to play with my 20 FP pro Elite after a few years break - what a gun

Lucky son-of-a-gun....

Typing of the 77, I've had a few over the years (first one way back when they were the new kid on the block in 1983 or 4, cost £115 from Adams in Darlington...long gone now ) and a few TX200s too, and one thing I thought they all needed was a seating nipple on the transfer port, can't quite remember what Jim Tyler found when he experimented with pellet seating, but thought it would save my thumb. But back to the idea of the sliding breach arrangement, BSA did exactly that with the Goldstar (the original rotary magazine spring gun, not that old two wheeled thing or the new wind in the tank thing they do now). Shame there are no spares available, though I suspect if the Goldstar uses the same piston washer as the others in their Superxxxx range, then it stands to reason the outer cylinder must be bigger to house the compression chamber and one wouldn't fit the RB2.

[Shed tuner]

yeah, the goldstar has a pretty fat cylinder, I think 28 or 29 mm bore. Mine has also long since gone.

Ref the seating nipple, I did experiment with a transfer port sleave on TX that was left deliberately slightly protruding, such that it woudl seat the pellet ~0.75mm into the bore. It was very consistent, but did cost me a bit of power - I think it was too deep; something like a 0.3mm protrusion would probably be good.

[look no hands]

yeah, the goldstar has a pretty fat cylinder, I think 28 or 29 mm bore. Mine has also long since gone.

Ref the seating nipple, I did experiment with a transfer port sleave on TX that was left deliberately slightly protruding, such that it woudl seat the pellet ~0.75mm into the bore. It was very consistent, but did cost me a bit of power - I think it was too deep; something like a 0.3mm protrusion would probably be good.

It might even be around the 30/31mm mark, I remember stripping one many years ago and the piston came out the main body tube without having to remove the maxi grip rail (which you can't do with the Superstar), the pistons seem to be different (according to Chambers) but the piston seals are the same part number for the Supersport/star and Goldie, which means 29mm, so the inner compression tube must add a couple of millimetres to the total.

Pete

[Shed tuner]

It might even be around the 30/31mm mark, I remember stripping one many years ago and the piston came out the main body tube without having to remove the maxi grip rail (which you can't do with the Superstar), the pistons seem to be different (according to Chambers) but the piston seals are the same part number for the Supersport/star and Goldie, which means 29mm, so the inner compression tube must add a couple of millimetres to the total.

Pete

yeah, I meant the actuall compression tube, so 29mm makes sense. must be at least 1mm wall, so 31mm ID for the action tube, which in turn would be at least 1.5mm wall, so 34mm OD at a guess ? Big beastie.