Hi
is it worth to try or buy a bushnell banner 6-20 x with mil. dot reticle?.
regards
yes

depends on your use and pocketbook - actually i've had pretty fair luck out of them, just never tried one with that much power. got one in 5-15 thats pretty good, only complaint is the crosswires are a bit heavy, but i find that with most mildots

The cheaper Asian-made leader line scopes are iffy at best in any variable, and the higher the power the more marginal their performance. I would say that spending money on such a scope would in all likelihood be tantamount to kissing your money goodbye. Check what such a scope is bringing in resale on ebay and you'll probably opt for something else.

I think they are pretty good if you don't have them on a big kicker. I have owned a 4-12x and 6-18x, and have used a couple more on other people's rifles. The 6-18x 50mm seemed particularly good optically. Better than the 6-18x 40mm or 4-12x 40mm. I used them all on rimfires at not more than 125 yards.

Adjustment worked fine, held zero okay, optics were pretty good, not great. AO adjusted well and went as close as 10 yards. I am not a big fan of cheaper scopes from parts of asia other than Japan. Usually it is money wasted. These seemed okay though.

And I own some Nikon Monarchs, have owned a Zeiss, Elite 4200's etc. I do know what more money gets you in scopes. So if not using on a large caliber probably okay. Considering the lens and glass quality I might drop back to the 6-18x or 4-12x.