There are a couple version of '6x47' floating around over the last few decades...
There was one that was based off the .222 Rem Mag round, necked up to 6mm. Kinda before my time, not sure what the endearing traits of it were supposed to be - other than it (just barely) qualified for things like metallic silhouette (minimum 6mm bullet) and deer hunting in states that put minimum caliber restrictions in place. Fairly anemic as these things go - figure slightly more case capacity than a .223 Rem, but still less than a 6mm BR.
There was(is) a round called the '6x47 SM' or 'Swiss Match', which is AFAIK one of the rounds that D. Tubb looked very hard at when designing the 6X and then the 6XC. Dimensions and all that are *very* close between the two. Biggest problem was getting the brass stateside in any useful quantity proved to be dang near impossible.
Then there is the new/current '6x47L', or more properly '6-6.5x47 Lapua', i.e. a 6.5x47L necked down to 6mm. It is just a smidge under the 6XC in case capacity, uses a small primer and PPC sized flash hole, has factory available Lapua brass, and so far works out to be very, very capable. Think of it as a shortened, but hot-rodded, .243 Winchester. 105-107gr bullets running between 3050-3150fps with quite a bit less powder.
HTH,
Monte
