BSA BSA Supersport restoration

I have an old BSA Supersport which I recently did a restoration job on. I had originally planned to buy a tuning kit but after stripping and refinishing the stock and barrel and fitting new sights, I had already spent more than the gun is worth. In the end I just cleaned/re-greased the mainspring, piston and guides etc.
Today I ran some tests using the Chrono Connect app and I only got 335 fps and 1.9 ft. lbf. I'm confident the numbers are at least reasonably accurate.
I'm interested to know if those are ridiculously low numbers or within the range of what is considered acceptable given the age of the gun which I'm guessing is probably at least 15 years old?
I know nothing about the history of the gun although it was in neglected condition when I first got it.
 
the problem with the Supersport is there are so many but your is shooting like a dog
when you work on a project and go over budget you either have wasted your money on the front end to get it to say the point you are or doing the job right where you will have to go now
it is a slippery slope and many including myself have been on
info for you
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I couldn't see anything wrong with either. The mainspring was slightly bent. I'm not sure if that's an issue or not.
Old gun the spring could be just fatigued / lost its vigor or to say over relaxed from the years . Measure it up and see if are can cut you a fresh one .

Stock one still available

https://www.airgunspares.com/160672bsaasmercurymainspring.html

Not a bad looking gun

 
well that is my point
we all have been there, a project that goes over budget
the problem we have is we know the model but not the variant
as you probably know Knibbs might be your best choice
I'm pretty sure it's a Supersport Mk 1 (.177) which was manufactured between 1986-1987 according to your earlier post. That makes it much older than I had originally thought. It also shows it was rated at 850 fps.
 
The first picture shows a Mk2
Mk1 has regular 11mm dovetails cut right in the cylinder. IMO that's the one to get. The Maxi grip 14mm rail is an abortion.
The Mk1 is so much easier to work on. I have 2 minty Mk2 177 and .22. Couldn't ever find a decent Mk1.
Mine run 14 ft lb and no twang from the factory (hear that air arms and weihrauch?). Powerful little suckers and easy to cock too. Dead on cold hammer forged BSA (the finest) barrels. Never shot tight groups with them because I don't have scopes on them. And hard for me to see irons. Darn, I think I'll put a peep on one. (y)
 
You didn't mention the seal. Is that because the scope rail won't let you remove the piston? BSA use a pretty good spring. A little bend won't hurt.
No problem removing the piston. The seal looked ok to me but considering the age of the gun it makes sense to replace it along with the mainspring, breech seal, spring guides etc. which is what I plan to do. I read elsewhere that the MK 2 has a 3 point cocking lever and an external spring guide which means mine must be a MK 1. I agree with your comments about the quality. They are really well made guns.
 
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This is an old string but readers might still be checking it out. I bought my Supersport MKII in 1993. Although I enjoy shooting it, I don;t think I have put more than a half a dozen tins of pellets through it over the years. I have never disassembled it and don't place oil in the cylinder. I have only replaced the breach seal. I tested on my chrony this month (9-24), it registered 711 fps with RWS ,22 Meisterkugeln pellets. I repeated the test with similar results. This equates to 16 ft pounds of muzzle energy. Not bad for a 30 year old air rifle.
 
No problem removing the piston. The seal looked ok to me but considering the age of the gun it makes sense to replace it along with the mainspring, breech seal, spring guides etc. which is what I plan to do. I read elsewhere that the MK 2 has a 3 point cocking lever and an external spring guide which means mine must be a MK 1. I agree with your comments about the quality. They are really well made guns.
The Mk1 has dovetails cut into the cylinder. And will be so much easier to work on
Some Supersport trivia:


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