Haven't been following this thread but just read thru the last 15 pages, I do gotta say that if this was happening to my rifle after 300 rounds it would be sent back to where i bought it from for full money back refund, or at least in store credit, imagine what is going to look like after 3000 rounds? 10 times the damage pictured. I'd get out before this rifle literally eats itself and your pocketbook up completely
You are late to the party, as we have already beat this topic to death. Those marks are all cosmetic in nature, aside from the peening which is occurring to the aluminum Action Cover at the corner with the ejection Port and Cocking Slot. I expect that the peening will soon subside. In any case, nothing whatsoever is being "eaten up". Take a look at a Swissarms rifle after 300 rounds without protective tape around the Ejection Port and you will see similar cosmetic "wear and tear". The only difference is steel casings hitting a steel Receiver on the Swissarms, versus steel casings hitting an aluminum Action Cover/Handguard on the M10X.