Yes and no. Yes, they work, but you are limited to three bullets total that are even decent- if you can’t find those, there are no other alternatives. And, in something like a 25CM- there is no factory ammo. The .257 is like .277- the support just isn’t there.
No, it doesn’t do the same thing because 133-135gr bullets causes enough muzzle movement to be noticeably less “shootable”. A couple of ft-lbs difference in recoil makes a noticeable difference in spotting shots.
8.5lb riles-
6cm 120gr= 11 ft-lbs
25CM 135gr= 13 ft-lbs
16% more recoil
6UM 120gr= 19 ft-lbs
25UM 135gr= 22 ft-lbs
15% more recoil and in cartridges like these it matters, as the 6UM is already at the limit of spotting one’s own shots for good shooters.