euroarms tend to have the same chamber dimensions as Pietta. .375 should be good if there is a tight swage-down upon loading whether or not ring gets shaved. Uberti has somewhat larger chamber mouths and often prefers a .380". I've found that Speer balls are round and their .375s work in my ubertis. Hornady balls are often a bit lopsided and will slip into the chambers with no friction.