I ran into the issue of the locking block failed on my light 12. it is the thin rail style. I know it was produced before 58. Looking at the serialization L 48726 it was produced in 1955. I was lucky enough to find on Ebay almost the entire assembly minus the locking block latch and spring. I removed the locking block, the rail and track were in what looks to me excellent shape. I cleaned and reassembled. I measured the original breach block and the purchased block. very slight differences (+/- .001) on points I measured on the block rails. I reassembled using the purchased assembly thinking from what I am seeing I should not run into any issues. I wanted to reach out to see if there is something I'm overlooking, and should I be using the original breach block and the locking block from the purchased assembly? Also, I replaced the action spring the block was hitting the back of the receiver. I'm thinking that was the root cause for the failure.
I agree with Rudolph. If you have them and they are in good shape re-use. If not go with what you got, and it will be fine. No need to measure. Can you post some pictures of the back of the receiver?
Thank you both for the feedback. The original breech block is in good shape. I will go with original on both of your advice. I tried to attach 2 pictures with to the reply post but I receive an error that I do not have permission to view or perform this action.
Good move on you changing the action spring. Saved yourself from later heartache that’s for sure. Not a clear image but looks couple of minor marks, like you caught it before it peined hell out of the back face. I have seen a B 80 that stretched the steel so bad it cracked.
The field manual lead me to the decision on changing it. I was reading through the manual and It mentioned impact marks on the back of the receiver.
