I could go into something long winded here but I don’t want to. So let’s attempt to put Your mind at ease. You have measured Your current lug and it is certainly accurate enough for Your stated shooting purpose. You have asked the advice of a very knowledgeable and helpful person, and he suggested using the lug you have. I agree. Put Your rifle together and start shooting. The target will tell You if something is wrong. And I’m willing to bet right now it won’t be the recoil lug.

Getting more long winded, for Your(big game) hunting purpose, You only need to hit a 10” pie plate at what ever distance You are shooting. Easily achievable. For 500 yard target, that kind of accuracy gets boring fast. A hunting rifle is a hunting rifle and a target rifle is a target rifle. I and others here have been where You are. Put Your rifle together and go have fun. Your targets will tell You what You want to do next.

I could go on but hopefully this is enough JMO