BSA Superstar with Theoben Gas Ram Conversion, a few questions...

[cartertools]

I recently stripped my BSA Superstar that has a Theoben gas ram conversion, because it was shooting a little slow. This is what I found, and I want to make sure that things are as they should be.

http://www.mechanicalphilosopher.com/08220801.jpg
Here are the Theoben conversion parts that I found in my rifle.
http://www.mechanicalphilosopher.com/08220802.jpg
The setscrew is threaded through the end cap, fits through a hole in the cross pin and bears on the end of the gas ram.
http://www.mechanicalphilosopher.com/08220803.jpg
Here's a cutaway view. All the force of the ram is taken by the screw through the scope rail on top and the stock screw on the bottom. This probably explains why my stock screw was stripped at the end. In order to take the stock off, you have to unscrew it. But it's under a small bit of tension, so as you remove it, it's rubbing against the tube with some force. If the setscrew could be loosened before removing the stock, this would eliminate that wear.
I am not crazy about the fact that this conversion bypasses the cross pin.
http://www.mechanicalphilosopher.com/08220804.jpg
The stock spring setup.
http://www.mechanicalphilosopher.com/08220805.jpg
The spring rests on the washer fitted to the spring guide on the left, and the force is transferred to the cross pin by the washer and the spring guide.
http://www.mechanicalphilosopher.com/08220806.jpg
With the stock setup there is no force on the scope rail or stock screw at all.

So my main question is:
Was this really how the Theoben conversion was made on the BSA Superstar, or am I missing some parts that would transfer the force to the cross pin?

And a few followup questions:
If the Theoben setup is the way it's supposed to be, is it ideal?

Would I be better off making a washer of some sort that could transfer the force to the cross pin?

Should the setscrew be screwed in to just touch the end of the Theoben ram, or should it be used to provide extra preload?
Here are the two blog posts showing how I disassembled the Superstar:
http://anotherairgunblog.blogspot.co...ar-part-1.html
http://anotherairgunblog.blogspot.co...ar-part-2.html

[POK!]

I have had 2 Superstars fitted with gasram. Both rams had a disc which fit the crosspin like the spring guide washer, the crosspin taking the force of the ram. None had the setscrew in the endplug. I rememeber one rifle failing to cock if a piston washer was mistakenly left inside the piston so there can't be much room for any preload adjustment.

[lightning22]

Originally Posted by POK!

I have had 2 Superstars fitted with gasram. Both rams had a disc which fit the crosspin like the spring guide washer, the crosspin taking the force of the ram. None had the setscrew in the endplug. I rememeber one rifle failing to cock if a piston washer was mistakenly left inside the piston so there can't be much room for any preload adjustment.

Ditto on mine.

That's an interesting modification, obviously with unintended consequences.

Rich

[bengarzy]

Originally Posted by cartertools

I recently stripped my BSA Superstar that has a Theoben gas ram conversion, because it was shooting a little slow. This is what I found, and I want to make sure that things are as they should be.

http://www.mechanicalphilosopher.com/08220801.jpg
Here are the Theoben conversion parts that I found in my rifle.
http://www.mechanicalphilosopher.com/08220802.jpg
The setscrew is threaded through the end cap, fits through a hole in the cross pin and bears on the end of the gas ram.
http://www.mechanicalphilosopher.com/08220803.jpg
Here's a cutaway view. All the force of the ram is taken by the screw through the scope rail on top and the stock screw on the bottom. This probably explains why my stock screw was stripped at the end. In order to take the stock off, you have to unscrew it. But it's under a small bit of tension, so as you remove it, it's rubbing against the tube with some force. If the setscrew could be loosened before removing the stock, this would eliminate that wear.
I am not crazy about the fact that this conversion bypasses the cross pin.
http://www.mechanicalphilosopher.com/08220804.jpg
The stock spring setup.
http://www.mechanicalphilosopher.com/08220805.jpg
The spring rests on the washer fitted to the spring guide on the left, and the force is transferred to the cross pin by the washer and the spring guide.
http://www.mechanicalphilosopher.com/08220806.jpg
With the stock setup there is no force on the scope rail or stock screw at all.

So my main question is:
Was this really how the Theoben conversion was made on the BSA Superstar, or am I missing some parts that would transfer the force to the cross pin?

And a few followup questions:
If the Theoben setup is the way it's supposed to be, is it ideal?

Would I be better off making a washer of some sort that could transfer the force to the cross pin?

Should the setscrew be screwed in to just touch the end of the Theoben ram, or should it be used to provide extra preload?
Here are the two blog posts showing how I disassembled the Superstar:
http://anotherairgunblog.blogspot.co...ar-part-1.html
http://anotherairgunblog.blogspot.co...ar-part-2.html

Thats how they were 10 years ago!

Ben

[cartertools]

That confirms that it's not the ideal setup. I think I'll put it back together with the stock coil spring instead of the gas ram.

Ben (bengarzy), so you have seen Theoben conversions like mine? Any idea who did the conversion that way?

[Gwylan]

Originally Posted by POK!

I have had 2 Superstars fitted with gasram. Both rams had a disc which fit the crosspin like the spring guide washer, the crosspin taking the force of the ram. None had the setscrew in the endplug. I rememeber one rifle failing to cock if a piston washer was mistakenly left inside the piston so there can't be much room for any preload adjustment.

Mines the same, when you say "Theoben," i think you mean "AWT."

Gus

[lightning22]

Originally Posted by cartertools

That confirms that it's not the ideal setup. I think I'll put it back together with the stock coil spring instead of the gas ram.

Ben (bengarzy), so you have seen Theoben conversions like mine? Any idea who did the conversion that way?

Bengarzy is the Ben in 'Theoben'

[cartertools]

So that means it was a factory conversion! Interesting...

This points out why I came with my question to the UK forum...

Originally Posted by lightning22

Bengarzy is the Ben in 'Theoben'