Superstar\ RB2 .25 rotary breach

[gary_c_ham]

does anyone know the allen key size for the grub screw that fits in the rotating breach on a superstar? are they loctited from the factory? is there a knack to getting them out?

[edbear2]

does anyone know the allen key size for the grub screw that fits in the rotating breach on a superstar? are they loctited from the factory? is there a knack to getting them out?

Take great care with making a note of the exact distance it is in, and also use Loctite 243 when re-fitting if this is the grub that protudes into the air passage transfer as per RB2 Airsporter.

I re-built a RB2 (which had never been apart since new) a few years ago, and removed the grubscrew and neglected to measure exactly how much it stuck out into the airstream, I then had several times to strip the gun as it would not make more than 8 ft/lb despite all my efforts.

I left the screw in the position that seemed to make the most power, which was just over 9 I think, but was at a loss, all new inside etc.


I spoke to Jim Tyler about this and he said "air leak"......I said "what....down past a grub screw????"

I had not Loctited the screw.......I used number and letter drill shanks to measure the screw height into the transfer, then removed it, re-fitted it to the correct position with Loctite and left 48 hours........It went straight to 11.3 foot pounds

So if you are thinking it will alter the power, you may be right, but you may also be giving yourself hours of grief.

ATB, Ed

[gary_c_ham]

thanks for the reply. Any idea what the allen key size is?

Take great care with making a note of the exact distance it is in, and also use Loctite 243 when re-fitting if this is the grub that protudes into the air passage transfer as per RB2 Airsporter.

I re-built a RB2 (which had never been apart since new) a few years ago, and removed the grubscrew and neglected to measure exactly how much it stuck out into the airstream, I then had several times to strip the gun as it would not make more than 8 ft/lb despite all my efforts.

I left the screw in the position that seemed to make the most power, which was just over 9 I think, but was at a loss, all new inside etc.


I spoke to Jim Tyler about this and he said "air leak"......I said "what....down past a grub screw????"

I had not Loctited the screw.......I used number and letter drill shanks to measure the screw height into the transfer, then removed it, re-fitted it to the correct position with Loctite and left 48 hours........It went straight to 11.3 foot pounds

So if you are thinking it will alter the power, you may be right, but you may also be giving yourself hours of grief.

ATB, Ed

[edbear2]

thanks for the reply. Any idea what the allen key size is?

Sorry, too long ago..... I looked at Chambers drawings but the breech block is just a single part number, It surely is just a case of trying different allen keys till one fits?..

ATB, Ed

[gary_c_ham]

1.5mm seems too small, 2mm too big.....

Sorry, too long ago..... I looked at Chambers drawings but the breech block is just a single part number, It surely is just a case of trying different allen keys till one fits?..

ATB, Ed

[Phil Russell]

You have me puzzled. I recently stripped and resealed a Superstar in .177 and do not recall having to remove a grub screw or whatever on the breech with a hex key to do so. To get at the rotary breech you need to strip the piston out then remove the breech lever ... it just comes out with a bit of leverage but watch out for a small flat spring there. The rotary breech then slides back down the cylinder just like the piston does and exits at the back of the cylinder.
Or do you refer to removal of the end block that is secured by a trigger guard screw from underneath and another screw from on top etc
Cheers, Phil

[edbear2]

1.5mm seems too small, 2mm too big.....

Sounds like 1/16'' Imperial then, that's about between the two, Invest in a good set of imperials I would say, ATB, Ed