Hmmmm I used to have a Swinburn sporting Martini in 577/450 but cannot recall the extractor however I don't recall it lookign weak!. As for inaccurate ................. Hmmm I didn't notice that either. Mine did shoot high until I discovered that the ivory bead had been broken off. The entire foresight blade and bead was made from Ivory. Luckily a piano restorer gave me a small piece of new Ivory and I managed to make a new foresight insert up. The rifle had "Battaue" sights in that the rear sight was a pyramid with two ivory triangles inset into the face with the usual stand for 100 yards and foldign leaves for 200 & 300 yards with a ladder sight for 400-800 yards if memory serves me correctly.

On Bisleys old Shorts range (200 yards) once a load was found that regulated to the sights Deer huntign with it would not have been a problem

the bulelts were 480 grain lead Paper Patched using FO Triangle Black Powder. I wud need to look up my notes for the charge etc.
I traded the rifle with a friend as it had been restored and re-blued and I wanted one in more original condition but have never found another. Those at auction tend to bbeyond my mearge means

Here are the few photos that i have of it:-

That shows the new Ivory Blad/bead that was made up

It was purchased at the same time as the Wm Powell retailed BSA sporting rifle shown along side.