I picked up a $25 Brinks sealed box from the Sun Trust bank to hand sort since I do not have a Ryedale. The first roll I opened yielded zero copper. I weighed the zinc roll which is 125g (2.5g x 50). I then weighed every other roll in box and was the same. So this means someone in my area is sorting for sure. If you have a digital scale, weighing the rolls can save you much time. The last few rolls I got from the Credit Union were much better, ended up with 9 Wheats and about 32% copper.
When I get skunked on my first machine roll of a batch I look at the coins at the ends of the other rolls. If it's all newer stuff too I just assume the coins inside are the same. Odds are if there were anything in there it would show on some of the ends. That happens to me with (cdn) dimes a lot (all post-1999 steel, no nickel or silver).
Yes, weighing the rolls can certainly save you time. Weighing the boxes is even better. An all zinc box will weigh about 14.08 pounds. If they are new, great! If they are circ, just deposit them on your next dump.. already rolled and boxed.
I get about the same percentage from Brinks rolls as any other rolls, including CWR. I actually trade several boxes almost every day to one of my banks for fresh Brinks boxes. I have gotten really good at opening Brinks rolls.
If your percentages are low.. just sort more. If your percentages are high.. just sort more.
Now selling Copper pennies. 1.6x plus shipping. Limited amounts available.