As I saw that three posts here said that they use a 12/15 BSA Martini's in the bulging R/F cases post I thought I would start a new one as I didn't want to hijack that thread and as I have seen other posts here saying they get under half inch groups at a hundred yards and had assumed they were using special target rifles or barrels to get that sort of accuracy.
This is my BSA Martini R/F barrel which I had threaded for a silencer and shortened to twenty inches that came with the action.
I think it must have a tight chamber as occasionally a case from RWS Rifle match needs a firm push to get it to chamber. All other types of brands go in no trouble and no bulging cases.
I have also used Lapua and Eley match without much success. Around one and a half inch groups off a sand bag. Never any better and quite often worse.
The only thing that has been done to this rifle is a shortened barrel and a new stock.
The trigger is a perfect light let off as one can come to expect from a BSA Martini.
I have bore scoped the barrel with my new $14-00 bore scope and it all looks ok to me.
I have put my poor accuracy down to mirage or wind, forgot to mention it is topped with a Burris 8x32 scope which I generally use at around twenty to twenty four depending on the day.
Is this rifle capable of better accuracy than I am getting and is all down to my lousy shooting?

Nero:    Looks like a fine rifle.  Easy to tell if its you or the rifle. Find a crakerjack rifle shot and have him shoot your rifle.  Anr / or you shoot his matchwinner.  You will know.............                              Best        andy

Nero,
Have you tried resting at different places on the forearm?  That had an effect on the Martini I had.

JS

My 12/15 will shoot an inch group or slightly better at 100 yds with the original sights and terrible eyes.

Your small martini centerfires--are those converted Cadets or 12/15s? Thinking about doing a conversion myself.

I see that's a takedown - might be some issues with barrel to receiver fit?   
Also, .5 in ch groups at 100 with a .22 isn't 'normal' accuracy.  Don't forget the .22LR is notoriously fickle to shoot, and extremely sensitive to any variation in holding, position, grip,...  1.5 inches without extensive trqctice doesn't seem unreasonable.
Also, when changing ammo, you'll need to shoot about 20 shots before it will stabilize and shoot to potential.
It's MUCH easier to get MOA accuracy with CF than with .22lr...

Nope its not a take down but your post sure made me feel better.
I haven't done any practicing with this rifle and have only used it for rabbit shooting until recently when our club put on a competition for R/F at a 100 metres at our range.
Any R/F rifle and can use a sling and a jacket. Which is why I had the aluminium rail put on the bottom of the fore end and put a hand stop from a BSA International on and got out my old target shooting jacket that I haven't used for years.
Thanks guys for all the input its appreciated.

Not trying to unnecessarily stir the pot too much, but I have found some ammo (RWS) likes  fairly clean barrel, but other (Federal) likes well fouled and doesn't seem to shoot real well until after 50 shots. YMMV 

Shot it for grouping off a rest and a sand bag under the butt prone.
After reading about the half inch starter groups posted here, thought this was the norm.