New to forum. Of coarse I didn't come without a question

Recently acquired a New M1A Super Match, Pre-Ban. I was helping a friend sell some weapons and I couldn't resist this one for myself, as I've wanted one for years.

I took it to the range a week ago. Shot some Winchester factory ammo threw it. I noticed the the Op-rod showed some brassing, where the rod was obviously hitting the empty shell casings as it was moving forward. Even nocking some of them into the walnut stock, marring the wood.... grrrrrrrrrrrr.

First thought was the factory loads were to heavy.
I loaded some of my own last week, using a military match 173 grain BT, and 40.3 grains of 748. Pushing it about 2275 fps. Figured it was slow enough. Went to the range today, and I still am seeing this marring.

Whats up? any help would be apperciated.

By the way,,,,,,,,,beautiful rifle!!!! Never skipped a beat and really groups. I have a new addiction!

Scott