I have a M17 I re-welded ears back onto. Luckily like yours, enough of the base was left to mill off for receiving the "ears" and then they were wire fed welded back in place.
The donor ears came from the rear portion of a destroyed receiver half and luck was in my favor because the holes for the rear sight leaf were still intact on both parts. So I only needed the very top portion of both sides.
The hardest part was the long taper on the port side at the rear on the m17. The inside was kind of hard to do cleanly too.
Your rifle appears to have a little bit different construction at that portion evidenced by the pictures.
I notice some blind pins that can be seen in the picture, could you tell what they are for if you don't mind?
Also it would be interesting to see how the clip loading slot is manufactured into your rifle.
I never had the opportunity to see a 276 rifles up close.
I think the progress you made so far is impressive and a worthy effort.![]()