it's a brand new 18v DeWalt DCD950KX hammer drill, $300.
If it's brand new, and putting a normal twist drill into it shows that you're not hitting metal, maybe you can take it back to the store for a refund. That's what I'd do.
Calling a tool that can't drill a 5/32 inch hole more than 1/4 inch deep into concrete a "hammer drill" isn't just misleading advertising, it's fraud.
You might just have a defective product, too. Any hammer drill, even a cordless one, should be able to do what you're wanting to do.