Hello Everyone. New here as of today!
I wanted to post here to help anyone that might have the same issues the original poster was having. I recently purchased a new Winchester 1873 SRC through cabelas (5/2023). It's the "competition carbine" same as original posters rifle. 357/.38sp
I was also having the same jamming problems, and my carrier block looked the same as in his pics. If I ran it slow or fast I would have hang ups. I ended up removing the carrier block and filing/sanding down the right side of the block so it actually had a beveled edge/contour. This helped with my ejection issues. I hope this helps anyone in the future!
-Thanks