OT: Realistic expectations for DoD Engineer grade

I'm now looking at DoD engineering jobs and the advertised GS levels are spread pretty far. I've got a BSME and was a licensed PE (mechanical) until a couple years ago. After graduating, I worked for a company as field service, project manager, sales and I&C design; approximately 9.5 years total. For the last 3 years, I've been on my own doing manufacturing and fabrication, mostly of in house products. So my question is for anyone who might have gone through this process or just happens to be familiar with it. How could I expect to be classified given my general experience (which was water and wastewater in nature) when applying for a general or mechanical engineering position?

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