Nothing except the stock 7.62 x 39, sorry. Caliber conversions are not just a matter of changing barrels. I recently did a custom barrel for a customer that wanted something a little different. The O.D. of the ribs are as wide as possible while still being able to use the original lower hand guard :
We had it Nitride finished after machining and it came out as one of the nicest I have done.
Leigh