Bill The takeup ring is a very small part . It,s how the bolt locks up in the reciever . Most model-12,s will if not fix,t ruin a reciever if it does not lockup well . Alot of the time it,s a worn out action rod that does the damage I sent you a PM
The very first test I do on a mod. 12, is feel the recoil lug machined into the top of the receiver. If it's flared at the bottom with a lip you can hang a fingernail on, it's pretty worn. Mainly due to what Alf-99 said above, a worn out action rod not properly seating the bolt in the cut-out lug when the gun was fired, many times.