The ACC Premier Gen 1 was discontinued, but we do offer our ACC Premier Gen 2 for the CZ 457.
Defiance states that some of there actions will fit Remington 700 inlets and others will not. MDT makes a MDT ACC Chassis System for the Defiance XM Action however we currently do not have that particular model. If you have a different Defiance Action other than the XM model I recommend contacting MDT to see if the Remington 700 models will fit your particular action.
The MDT ACC Chassis System does come with the vertical pistol grip.
Yes, the MDT ACC Chassis System will work with the Tikka T3X CTR.
The MDT ACC Chassis System fits most Remington 700 rifles with a max barrel diameter of 1.350" . However, the forend length of the chassis is 17" - 18" depending on the model and will extend past your barrel. If you have a muzzle device with a larger outer diameter than 1.350" it will not work. You could always remove it but once again, the forend will extend past your barrel.
The CZ 457 does not have the exact same specs as the 455. It wiil not be compatible.
Yes, this will fit your Tikka T3X .308. You would need this specific model: 3JN-RS0-ACCCS-104073-BLK
No, MDT does not currently offer a left hand ACC model compatible with long action Savage models.