The weight of the frame is not what really makes the weight of the bike. 20% is probably accurate. Any given decent quality frame no matter the material will vary by a mere pound or two at most. I have a Giant Rincon that started life as a 35lb bike and with high end components now weighs in at 24lbs. When I stripped the the bike to the frame and weighed it. The frame, while a little more heavy than my other frames, was still only barely 4lbs. My Mamasita was 3.5 lbs (24lbs whole) and my Fisher Superfly is 2.5lbs. (23lbs whole same components as the Mamasita) All in 20in size.
Pretty much any frame is going to be between 4 and 5 lbs. So what you really have to decide is how much you want to spend and what geometry you like. I think I'm going to order a Gunnar Rockhound if for nothing but it's pretty reasonably priced for a handmade and custom painted frame. Someone posted that they are 853 Reynolds but that isn't true. Waterford/Gunnar uses True Temper OX Platinum.
Now this is a $900 frame. Is it better than a bike that uses 4130 steel? An On-One frame is going to be around $300 and is made of 4130. Is the Gunnar worth the extra $600? If it's just for the steel and weight I'd say no. 853 or TTOX is going to be a little lighter; a pound at most. It could be stiffer, but that depends on the quality of construction and geometry IMO. The both IMO feel like steel. Softer than aluminum. Also consider geometry. Do you want an Race bike, a little more relaxed XC bike or something that wants a longer travel fork? The nature of the average hard tail rider puts them into XC with an 80mm fork and most high end steel frames have more aggressive XC race geometry.
I say also to avoid the retardation that is worrying about the static weight of your bike. Too many people put IMO to much emphasis on weight. Many will sacrifice performance for weight. Nevegals are heavy tires but they are freaking awesome. Save weight were it actually might count, like the wheels. I say might because I think some people who say they climb better on 1500G wheels over 2000G wheels and they can really feel it ETC are exaggerating at best and it's placebo at worst. I mean one 1lb of rotational mass might make a minute difference, but a difference that you can feel? Can you tell the difference between a bike with a waterbottle and one without?
