A QUALITY firearm will shoot any ammo!
A gun designed for steel case? Really? And what unique parameters would that require? Chrome chamber? Certainly a good idea but the Mosin Nagant never had it and has shot many millions of rounds of steel case. Same for the 1911 (WWII issue was often steel cased.) or my Thompson. Adequate chamber size? Decent extractor?
Damage a transferable HK - how? Wear a barrel? So does any other ammo. That can be replaced - the receiver is the registered part. You shoot it, the barrel wears. Any gun, any ammo. The only HK rifle extraction issue I have ever had has been an aftermarket barrel that was not made right.
I'm sure if I buy high priced ammo my barrel wear wwill be less as I can't afford to shoot it nearly as much - duh. Side note - much hunting ammo is unsuitable for machine guns! Primers are MORE sensitive and not crimped in place. CAN lead to slam fires and blown primers, both of which CAN lead to a KB. From that one MIGHT make a case to ONLY shoot surplus or Wolfe.
I have found Wolfe less consistent than top quality ammo - duh! Still good enough for man sized targets at reasonable range. If you want a sniper round, handload it. Buy the cheap Wolfe and PRACTICE. (If your gun is of adequate quality to shoot it!)
Right now, Wolfe is second choice in .308 because there is still plenty of cheaper surplus on the order of $.12 a round.