I had a look at a 4-16x44mm Sig Optics Tango 4 for the NZ Guns & Hunting magazine about a month ago. It reviewed very well I thought given the feature set, price point and the market it is aimed at. It came with the voucher for the free Sig Ballistic Turret (SBT, bdc as you mention), dialled well, zero stop, good reticle, great illumination, awesome warranty and had a bunch of other cool features. Low light performance of the glass wasn't as good as I had hoped and it wouldn't really be good for a long range set up where you might want to dial more than about 3MIL of windage. As I said though for the feature set, market and price point I thought it reviewed very well.
No experience with their Whiskey or Romeo range though.
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