Bill,
That depends, sorry to be vague, on how the insert was put in. Some are pressed,some are soldiered (soft or silver) and some use an adhesive such as Black Max. Also I beleive the 7.65 Argentine is a longer cartridge than the .308 as well as the bullet diameter of the 7.65 is .313 and the 308 is well .308 so you would want to slug the barrel to see if if has been replaced. Finally you don't know how the bushing was inserted, did they bore the chamber out to a cylinder or make the bushing the same dimension as the 7.65 round. In other words you might remove the bushing and create a larger problem.
If the bore is the correct size for the 7.65 round it might be easier to recut the 7.65 chamber but you will want to check the dimension of both cartridges.
Its not mine but personally, if it shoots well, I would live with it. If it is not grouping well and the gun was not rebarreled a thought might be to try a slightly larger diameter bullet to see if that improves groups.
Good luck...
WBLDon
