From my recollection the 6x42 is an older scope that came out in the 80s?, a time when 1" was pretty much the usual tube size.
Dont think I have come across a 30mm tube one but am curious now.....oh and I still have one on my Steyer-Mannlicher!
Swaro 6 x 42 was only made with a 1" tube. As Bryan said, if you get the chance, grab one. They are out there from mid £200 upwards. Swaro also do an 8 x 50 with a 30mm tube, again there are a few out there new. Try Bushwear or R Macleod in Tain, but expect to pay a fair bit more.
Thanks guys- I couldn't agree more. I have a 6x42 Swaro on a ruger Stutzen and love it so much I'd like one for my Ron Wharton of Rigby .275. Thing is it has fitted Redfield style adjustable scope mounts with......30mm tube. Sounds like I'll have to stick with the S&B on that one!
Also considering changing an S&B 8x56 for the equivalent Swaro on another rifle- but only if it is shorter and lighter (which I suspect it will be)- hence that separate query.
In answer to your question the Swaro 8x56 is both lighter and shorter than the S&B 8x56. The Swaro is 15% shorter at 13.25" vs 15.27" and lighter at 495gms vs either 560 or 605 gms (the S&B site is confusingly listing both weights for the non-ill 8x56) - that means somewhere between 13 and 22% lighter. I declare an interest in that I am selling my Swaro 8x56 on here.