I have a 1902 roller, 7 x 57, with a bad barrel, a sorta heavy half octagon unchambered .224 barrel of unknown origin, and a Lyman Alaskan scope.   

Been thinking about something that would use milsurp 5.6 mm ammo.  Bad idea?

I’ve got a high wall that was done in 22 Hornet, it’s definitely fun to shoot!

rotary or sliding extractor?
I have a take off barrel in 22 k-hornet, sliding extractor
for the shipping if you can use it
lot of snow here , take a couple of days for a pic

When you begin to push Rolling Block actions you not only get heads[ace issues, but you also ruin brass. Since the block rolls back it creates an angle to the bore which makes the rims bend at an angle. Once that happens there's no fixing the brass, and it wont chamber again without being oriented the same way it was when the rims bent.
Best to keep Rolling Block pressures under 25,000 psi, and avoid issues.

So what is the bolt thrust on the original 7X57 /45.000psi?
beltfed/arnie

The 7 x 57 with it's .472 chamber, would be 7874 @ 45,000 but, from what I can find, it was 46,000 which would be 8049.

The 7 x 57R is listed at 41,000 and that's 7174.

My 7 x 57 RB ate brass. The springy action stretched brass,  one reload maximum.  Brass stretched at head--I was timing brass and it stretched at the top of the brass at the head- stretched and sometimes separating.

That old gun shot oblong groups, taller than wide however.  Just now looked for my old log books but could not find any of them.  I think had a spreadsheet of some sort on 5-1/4" floppies I used in my Tandy 1000. That's long gone also.   But boy could the old 7mm RB shoot.  took AZ Javelina and Oregon blacktail with it.

I got it from Bill Hahn in Oceanside. Had a beautiful sporterized maple stock, California rollover cheek.  When Bill passed I often wondered who got his guns.  He had some interesting pieces. I traded that RB back to him for a 38-55 Highwall.  Had big plans for it.  Very plain working mans gun.  Shot it a couple of times right after  I got it.  Been sitting in the back of my safe now for 40 years.

Sorry just waxing nostalgic.