BSA Improved Model

[jirushi]

Hi, I recently bought a prewar BSA.
From reading John Milewski's great book "The Book of the BSA Air Rifle 1905 to 1939", I think it is an Improved Model (A).
The serial number cannot be read entirely anymore; this gun must have seen some life / had rust. But it seems to start with 126. See photos.

It looked quite tired. I lightened the stock a bit with fine steel wool and alcohol (being extra careful with the chequiering), and it is now getting a few layers of CCL oil.
I have made the metal a bit blacker by degreasing with acetone and then using Ballistol Schnellbrünierung. Some parts hardly had any finish left, so I thought this way the gun would have more protection for the future.

However, the internals need more attention than the exterior.
Power is relatively low (about 6.6 ft/lbs using .177 7,0 gr RWS). And it doesn't feel/sound right. Not a twang, but more a "boing".
The leather seal doesn't look great. At one spot, it is clearly damaged.
The piston has three phosphor bronze rings. I believe these should help sealing, or perhaps they are meant to reduce friction of the piston in the cylinder?
I think they do neither of those.
I tested their sealing capacity by removing the leather seal, and moving the cylinder up and down the compression chamber with my finger pressed no the transfer port.
Air clearly leaked past the rings.
Furthermore, they seem to make the cylinder move less freely through the cylinder.
Not sure why they are there; probably a tinkering project of a previous owner?

Then the springs. Twin springs, but one of them isn't flat section. It has a loose fit over the spring guide, or in the cylinder. Not ideal.
Together, they are about 21 cm (8,3") long. It is (too?) easy to put the trigger block back on the cylinder. I would expect more preload.

Hopefully the tap is ok. I will test it when I have a good piston seal.
Something that I noticed is that my .177 pellets don't fall to the end of the hole in the tap. In my .177 Light Pattern, they fall deeper.
I have tried RWS Meisterkugeln and a few types of JSB.

A few things on the "to do list":
- find or make a replacement leather piston seal. The usual parts shops don't sell this early flat type. It is about 5,5 mm thick. I might have to find a thick piece of leather and a 1.1" round cutter. Or try a 1.1" cup type seal (although I think this will reduce the swept volume quite a bit).
- find a flat section spring, or a pair of them.
- decide what to do with the phosphor bronze piston rings.

Any advice/input is welcome.

Many thanks, Louis



This stock length works well for me


Piston rings and damaged leather seal