I recently purchased a Marlin Camp 9 that had a destroyed barrel. I was able to locate a replacement barrel at a reasonable price (which is surprising since they are long out of production). Upon receiving the replacement I was met with a finer thread pitch than I was expecting. As you can see in the photo, the original barrel on the left is 20TPI and the replacement barrel is 28TPI (Thread diameter is 0.745")
I need to come up with a solution and am looking for advise/suggestions.
1) Wait around until I can locate a replacement barrel with the proper threads.
2) Cut 20TPI threads over the 28TPI threads and hope there is enough "meat" left.
3) Weld over the 28TPI threads and turn it back down, then cut 20TPI threads.
4) Save the ~10" of usable original barrel and weld on an extension to get over 16".
5) Apply for an SBR with the ~10" of usable original barrel.