Robin,

I've had no issues with a wandering zero in six years that I could attribute to the tube. Tube comes off for storage/cleaning, collar stays on. Tube goes back on in thee same place.

RE your wife's Valmet, lopping 6in off the Free rifle barrel would still give 23in of barrel, almost as Wuch as her Walther. Was she shooting it in UIT competition? I'd though that Standard rifles were mandatory for women until '97.