Is there any difference between a RF and a CF breech block on a Cadet action? Or is the block height just adjusted to suit the ctg? I note, on a RF action I have in hand, that the FP hole is pretty much centered in the breech block face, and it's just elevated relative to the bore to hit a 22 rim. If so, then CF conversion is rather simple, just lower the block by filing the lever cams and maybe truing the block face a bit. If not, then the conversion is much trickier requiring an off-center fp or filling and then remachining the fp bore.

they are the same the usual method is to bush-plug and redrill for someone who has done it before it isn't a hard job at all

the other things you may want to do is to drill the back of the receiver for rear cleaning rod - polish the entire inside and lighten the trigger spring

I've polished the body of the firing pin and the stop collar on the pin, polished the hole in the breech block where the spring is located and also polished the spring itself. Polishing the spring was a finger breaker, used various grits of silicon carbide paper and an old fluffy buffing wheel @1750 rpm. Couldn't really do the id of the spring but at least all the friction surfaces are bright and shiney. My model 12/15 already had the cleaning rod hole. A little dusting of moly powder doesn't hurt. Frank

Looking at it again, if I drop the block to line up the pin with the c/l of the barrel, the block will no longer be flush with the top of the action. 310s have the block flush. Ergo, the cf block must be dimensioned differently than the rf block. Also the "slide" is wider on the cf version .. so it looks like an eccentric firing pin may be necesssary. Unless there is a source of cf breech blocks, I can't find one.

I tore down a rimfire (thick wall) and a centerfire (kangaroo) side by side. The breech blocks appear to be the same overall dimensions, and the fp hole is in the same place, but

1. CF cam surfaces are cut deeper to reduce the height of the block (the levers are the same)
2. Front face of CF block has a bevel to deal with the higher forked extractor.
3. The "ramp" is wider and deeper to deal with the fatter ctg.
4. CF was relieved on one side for the cocking indicator .. RF did not have an indicator and was not relieved.

Somehow the CF breech block is flush with the receiver .. so I think the CF receiver sidewalls are a little lower. I did not measure them.