I've used them, yes they work, but expect more fouling and loss of accuracy. Lubed is a far better choice. Besides loss of accuracy and more sticky guns, cleaning the rifle bore is more of a chore. The fouling is like cement, not soft or softer like when using lubed.
If you swab the bore's every couple of stages it will help. The only reason I used them is because it's what I had on hand at the time, Now I still have a bunch loaded that I hesitate to use since going to lubed bullets for BP.
All that said I've been able to shoot local 6 stage matches with closer targets clean using poly coated bullets and no lube, but on a hot day with more distant targets.......ouch....I couldn't hit a thing!
Tully