Well, I used to use 147 bullets (ACME coated) and was happy with them. Read a lot of posts saying that 124/125 bullets are more accurate through the X-fives so I had to test 124 bullets. Sure, a bit more accurate and my splits seemed unchanged. So, last fall, I switched.
Today, I found some leftovers with the 147, went to my club for some practice and curiously shot 124s and 147s back to back. My finding today was the red dot returned more quietly with the 147 and I liked that. I did not notice this difference when I tested the 124 last year but it kind of makes sense.
I will get some 147 bullets and test them for accuracy. If good enough, I will switch back.