you mean they glued it all together? do they have a shorter one available.. if not there's a way around it.. machine a new adapter and turn off the original one.. I can't imagine that if it is just the threads that you would loose more than half a inch of barrel.. far as that goes, it's likely that the adapter could be re-machined on the barrel and rethread and if it is done correctly you won't notice any difference in accuracy.. unless it is a choked barrel.. that could be a different story.. but if it is not choked 1/2" isn't going to change accuracy more or less.. nothing noticable.. but it has to be recrown perfectly or you will have all fliers..
I still can't believe that I was able to shorten my notos barrel 4" and put inside the shroud a after market moderator and it's more accurate and quiet than factory.. I still need to out of curiosity check to see if the factory barrel was choked.. but you have to admit that taking 4" off the 11" barrel is a lot and yet it shoots better.. honestly I think a good even clean crown makes a big difference..
I'd offer if you could get a replacement barrel, so you are not out one to machine the end for you and then you could compare and see if you can tell any difference other than meeting the rules..
but I don't know the OD of your barrel.. my lathe through hole is 3/4 + and to get it perfect I work right at the chuck.. so I don't know if your barrel would fit..
id be happy to help you with it if I can, and if you can't get a barrel that's ok for the competition.. if you want help pm me and I will let you know if I can get it done in a reasonable time before my surgery.. I just don't want projects sitting around and someone wishing they had the part.. I'm very cheap, because I am retired and disabled and the machining is almost as fun as shooting.. and I am open to doing trades too.. actually I have lately only been doing trades or just for fun.. so if it's something I can help you with, the parts you order and shipping is going to be most of the expense.
glad to help if you want and if I can..
Mark