The 673 is made to look like the older 600 series but is built on the model 7 action. 1 1/2" for an average new shooter is not bad.
Most everone that makes a barrel can make one that can be used on your rifle. A quality barrel is not a simple bolt in job. It will have to be fit by a quality gunsmith.
Why do you think your rifle is not accurate enough. It may need a better cleaning. Maybe your rifle has a preffernce for one brand over another or of a different weight.
You have used how many loads, any 165 gr loads. Try some quality ammo compaired to standard basic ammo.
What do you have on it for a scope and are you shooting from a bench with front a rear rest? Put that rifle in the hands of a skilled rifleman and see what they can get out of it.
For a barrel change to a quality barrel if all your shooting is factory ammo you could still get 1 1/2" group with 1 or 2 factory labels, then one may shoot 1/2" Still have to find what it likes best.
Skill level ,your trigger pull, ammo used and the rifle rest you use can make a great rifle shoot like junk.