I am going to a auction this weekend where they have a Ruger single six 22, are all single six 22's capable of accepting the 22 mag cylinder or does it have to be a convertable?

As far as I know, you could have both cylinders fitted to any Single-Six revolver. Those labeled "Convertible" came with both, but the .22LR model can be retro-fitted.

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The Ruger SS came out in '53 but the first Mag SS didn't come out until 1960 or so. The Mag SS is bored .002 larger than the non-mag SS. I wouldn't try to shoot Mags in these older ones as they are bored too small.

Not saying it can't be done ---- Just that I wouldn't do it. The Mags (nearly all of them) are jacketed bullets, not soft lead.

The other question would be New Model VS Old Model --- I'm not sure that one cylinder fits the other.

When I bought and fitted a Mag cylinder on this New Model, I made sure I was getting a New Model cylinder (and of sufficient length).

Probably most SS's came through as convertibles. Not everyone even knows where the magnum cylinder is. I have two, and both shoot well with some ammo, and poorly with other brands. Not too shocking.

Even if you snag one with only one of either, Ruger can fit another. The .22 Magnum is much more effective on ground hogs or racoons than the LR, and if you need to do that, the option is worth having.

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FWIW, extra cylinders can have various length bushings, and be from either a New Model or Old Model.
Cylinders that are too "long" to fit in a frame can be fitted - but that doesn't guarantee the timing will be right (may side-spit); short cylinders are usually not usable in a larger frame, since if the rear is shimmed it affects headspace, the front shim give excessive gap (probably poor acccuracy & possible side-spitting)

As posted above, pre-61 guns have smaller bores, better suited for LR than for Mag - why Ruger started boring the barrels bigger after finalizing Convertible production.

I'm not saying it can't be done (I've done a few) - I'm saying you better know what your doing.

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