whats with all this scratches

[cst]

During load development I put a dummy round at the bottom of the mag to keep a consistent feed. When I extract the dummy round from the chamber I noticed these consistent spiral scratches around the whole diameter of the ojive and above. The dummy is a factory 123 SST round 2.250 and loaded a 123 scenar round out to 2.270. this first SST round, the marks are more pronounced since I used it all day but the scratches line up..the second pics are the ones I did at home trying to replicate it..the scratches are mild....No pressure signs
Lilja 319 barrel, ASC mags, Precision firearms bolt, Mega MKM upper.





I removed the extractor and hand fed the round and let it slam forward and then pushed out(with no effort) the round out with a cleaning rod......no scratches

it only leaves those marks when fed from the mag...

accuracy is not effected but a little disconcerting...4 round group at 100yards


Any ideas why this is happening? its a perfect spiral if you were to spin the round..