My 159 is currently at 1mm oversize but could do with a rebore as there is some light scoring after the small end spacer broke up. Is there a bigger oversize than +1mm or will that mean a new liner or scrap the barrel?

For the M159 onwards, the liner is thick enough to use the 340 piston, so you have up to the 340 standard size of 85mm plus oversizes

For the M159 onwards, the liner is thick enough to use the 340 piston, so you have up to the 340 standard size of 85mm plus oversizes

Thats assuming you can get hold of one. I was told by Dave Renham they are special order only from Spain and you know what that means. 1 expensive and 2 might arrive sometime. So good luck although if you only need a std size you may have more luck than oversizes.