well guess what.
to review, I have an original configured 243, with the monte carlso stock that I sent the recvr in for the new barrels, and a buff classic with the straight stock. When I got the BC, I tried for grins trading the barrels between the 2 recievers, and neither fit well in the wrong one.
Now, I tried my new 357 (fitted to the 243 receiver) in the BC receiver, and it fits well. Locks up tight, opens nicely.
So, yesterday I gave it a try. Shot the new 223, and then replaced barrels to the 357 in the factory fitted receiver, they both did well. THen I mounted the 357 on my BC reciever, and no problems at all -locked well,opened, and ejected on command.
I have, for the near future, solved my sight/scope issue. I am going to use the 357 with the open sights and the BC reciever stock. I dont mind putting a different barrel on it, I just was not interested in trading stocks and barrels on a single receiver. I know I would end up with stripped butt plate screws real soon doing that in addition to the un-handiness of the process.