You're talking to a Reformer. Have you known any of us to say anything in 25-words that we didn't take 250-words to explain? :O)
But I'll try:
oyu wanna see if it shoehorns - or, rather, why it doesn't into my "expiation/sacrifice" category?
I think a very powerful phrase about blood and atonement is "washed in the blood of the lamb" -- and what I think about again is that it seems in the Levitical system that the blood of the sacrifice is about sort of releasing or making available the life of the sacrifice - as if we didn't have enough life in us. Further there is the covenantal use of blood, to sprinkle on the people and on the altar - we are united in the blood of the sacrifice.
I'm just sort of reporting images here, trying to circle around the idea, and see what it looks like from various vantage points. And certianly Hebrews is the letter to go to for this stuff. What a great letter!