I had a 452 which was a lovely action, however it was the older one with the action screw going into the lug on the barrel. Along with the cost of upgrading the trigger and stock I decided to move it on and get a 457 Varmint.
As Ultimitsu says, it improves all of the aspects of the previous rifles that could have been better. The trigger is night and day better from the factory.
I've never had any thought of switching barrels for the same reasons as above - just not practical.
One aspect of the 457 that is a con compared to the 452/455 in my opinion is the shorter bolt open/close - in combination with the shorter, stiffer firing pin spring it is stiffer to cock on opening. I'm going to put a bigger and longer bolt knob on to add some leverage to help flicking it open with the back of my hand.
When I got mine there was the choice of the walnut stock or synthetic. Now there are more target/range shooting type stocks available I think that I would probably have preferred.
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