Marksman model 29 (aka BSA Supersport) tune

[baranjhn]

I had this for sale a several weeks ago but no takers; so it went back to the safe. Shortly afterwards, I decided I wanted to put in a Titan mainspring, spring guide, top hat and new seal. They took a few weeks to arrive from Countrystore Gunshop in the U.K. (formally John Knibbs). While I waited, I polished the piston and deburred any sharp metal I found. The parts arrived yesterday, so this morning I lubed the piston with teflon and the spring with Tune in a Tube. It was a pretty straight forward job and it went back together with a minimum amount of swearing and blood loss.

A quick rundown on the FX chrony gave me an average of 754 fps with Norma 9.1 FT domes for 11.5 ft. lbs. I'm pretty satisfied with the results and there is no twang now. In time as it wears in, I expect it to get smoother.

I mounted a period correct Bushnell Sporview 3-9x32, now I just need to sight it in.

 

[Steveoo]

Fairly experienced at doing these for shooters in the UK…
You need a fast start pellet …7.9 Crosman Premier usually giving the best performance. Chuck out the plastic top hat and try to add one of steel…UK shooters used £1 coins….The gun needs a tad of piston weight as they get a touch of piston bounce…..Basically, piston is a touch too big in diameter and wants to rebound on the cushion of air with heavier, slower start pellets…Had good results with 8.2 grain Superdomes if you cannot get the Premiers.
You will get much more velocity doing this ….up-to 890 fps known for these…and milder manners…
Your new guide rod will remove your twang. That seal you got works well and nice polish work..
Underrated guns once fettled, not to be confused with its horrible Lightning cousin.

 

[baranjhn]

The 9.1's were on my bench, but I'll try some 7.9gr Premiers too. I've got a few boxes of those.

Thanks for the info on needing a heavier piston. Next time I open it up, I'll try it out.

 

[baranjhn]

...You need a fast start pellet …7.9 Crosman Premier usually giving the best performance...
You will get much more velocity doing this ….up-to 890 fps known for these…and milder manners…

I finally had a chance to do a little shooting with her again. I gave the 7.9 Premiers a try and they were moving a bit faster. I still have nowhere near a tin a pellets through it, so I'm expending it to settle in more. I shot ten shots over the chrony and here are the results:

High - 821
Low - 793
Avg - 814
spread - 28
Std Dev - 8.5

The 793 was an anomaly and it affected the short string a bit. Overall though, she'd running around 11.6 ft. lbs. We'll see how she wears in over time.