There quite likely be a problem, I believe, with most jacketed bullets on this side of the pond. Unless they are designed for lever guns(like the 255gr. .38/55 bullets as-in Barnes originals, the 220gr. Hornady's and 200gr. Sierras,) they are not designed to expand much below 2,000fps, about 1,900fps minimum.

I recall that years ago, for Lions, the "Aluminum" cap on the .300gr. ST's were pried off to increase expansion. Nowadays, that old fairly heavy 'aluminum' cap has been replaced with something very much thinner. The last 300gr. ST factory loads I chronographed ran 2,474fps in a BRNO ZKK 602.

If there was an opportunity to expand at low speeds, I think a 235gr. Speer that was cup-pointed down to about 230 or 225gr. might work, as-would a standard 255gr. for the .38/55 in .375". For a heavier bullet, perhaps a 300gr. RN Hornady that was HP'd or cup-pointed might also work.

A centre-drill, makes for very easy 'cupping' on a lathe or small size. Chucking the bullet in the 3-jaw, then running the centre-drill in until the angle touches the jacket, then withdrawing the centre-drill leaves bullet so virtually identical weight, accurate and nicely HP'ed and cupped so they will expand at low speeds.

These bullets worked well for Rod after being sized down for use in a 9.3x57, at low speeds. Unaltered, even at 2,100fps impact speeds, they seemed too 'hard'.

Just a thought.