Interesting that someone should ask for a Colt Diamondback in .327 magnum. It sounds like a good combination. There used to be something called a .256 magnum based on a necked down .357 case. It was quite powerful (on paper, anyway) but used lighter bullets than the .327 would. It was catalogued as available in Colt revolvers in 1960, which seems to be my base year for all things gun-wise. However, I don't know if any were actually manufactured. The cartridge apparently did not gain a lot of popularity.
Another cartridge that appeared around the same time was the .22 jetfire or of a similiar name. It was also a necked down .357 using even smaller bullets. S&W made some k-frames in that chambering that came with inserts so .22 rimfire could also be used. There's a good chance that if you find one for sale, it will come with reloading dies.
I'd be happy with a Colt Diamondback in any caliber and I think I've seen as many S&W .22 jetfires as I have Diamondbacks.
I don't remember the model number of the S&W. Model 53, maybe?
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