I hate to use Hollywood as an example, but, every once in a while they do come up with some truth.I have read and heard say to use the same weight bullet that you practice with, is this a truism or falsehood ?
In the movie, The Outlaw Josey Wales, they talk about getting "an edge".
An edge is anything that gives you an advantage over your opponent.
If using the same weight and velocity bullet for practice as you use for defense delivers more consistent shot placement, then you've gained "an edge".
Granted, it's very slim, but, it's just that much more than the other guy has.
Put enough of them together and you just might overcome one of those pesky Murphy type things.