I first used the Barnes X bullets here in Aus in 1989 in 308 and 30-06 bolt action rifles.
The first Barnes X Aus Agent used photos of my recovered projectiles to promote the product and he sent me quite a few samples in different cals to test and also try to get more recoveries.
At the time I was doing most of my shooting with a double rifle so I specifically asked for projectiles for use in that gun.
Well, I shot a couple of hundred X's through it without problems.
This is an old pommie gun not a new double.

Another double of mine, (20 years old) has shot heaps of Winchester Fail Safe projectiles without any problems.
Same gun has shot heaps of Nosler Partitions without problems.
It's my opinion that any double that is not strong enough in the barrels to shoot Nosler Partitions without damage, is not worth owning.

But I don't shoot X's, Fail Safes, or Mono Solids through any of my doubles any more because there is no need to.

My idea of double ownership is to get it shooting right using the appropriate Woodleigh projectile then quit worrying about everything and get out there and hunt with it enjoy the thing.
Doubles can be a lot of fun!!!