I've seen thin stainless steel chamber inserts to allow firing .22 LR in a .22 Magnum cylinder. If you obtained these and shortened them you could fire .22 LR in a .22 WRF cylinder.
I've made a insert from a fired .22 Magnum case, which required sanding away some brass on the inside near the base, the casewalls appear to be thicker near the rim. Haven't used it yet.
I've fired a number of .22 LR and shorts in .22 Mag chambers of my Single Six and another off brand .22 Mag SA without any problems, no split cases or signs of leakage, but this may not be true of some brands of ammo or some .22 Mag chamber combinations.
The Colt Diamond Back is basically the same frame as the Police Positive Special/Detective special, but with flat topstrap and adjustable target sights and ventilated rib heavy barrel. These were made in .22 RF as well as .38 Special.
If a Diamond Back .22 RF cylinder were available it might be fitted to a .22 WRF chambered Police Positive (maybe if shortened at the front on a lathe). One should consult a qualified pistolsmith first to be sure there are no serious suprises in the dimensions.
I've had a few rim bursts with .22 RF cartridges, in both recessed and non recessed cylinders. Most of these were very old .22 Shorts with some external corrosion or signs of poorly drawn cases with rims hair thin. I suspect some older primer compounds could react with brass causing the rim to weaken or embrittle with age.
I've never had a modern manufacture .22 rim burst when fired in a non recessed chamber.
Last edited by Rainbow Demon; December 26, 2012 at 08:47 PM.