The short answer to you question is, it does fine. Here is part of the long answer at least how I see it:
There are plenty of posts on this site where Civil War buckles and mini balls have been found with the 250. I would say the answer to your question depends more on your technique, the site you are hunting, and what your definition of a relic is. Would I show up to an organized Civil War hunt with an Ace 250? Probably not. Does this mean if I did I wouldn't find anything? Again no.
I found a post on this site where there was a group of detectorists in Alaska shooting nuggets. They were pretty much getting skunked and then serious prospector's wife goes out with her trusty Ace 250 and finds a half ounce nugget a few steps from her tent! I think if you asked how is the Ace 250 as a nugget shooter, any serious gold hunter would tell you it isn't the right machine. That day it was enough of a machine. As Uncle Willy has said more than once (I paraphrase), if you want to find a gold ring, you have to first pass your coil over a gold ring.
If you are patient, as you appear to be, someday an item you do not expect will pop out of the ground where you least expect it. My first, with my Ace 250, was a civil war mini ball at the local freshwater beach (stuck under the root of a tree.)
Chris