The basic details of what's been kept are on http://www.nationalarchives.gov.uk/help ... p-to-1913/
Initially, at the time your chap entered the RN, :
"The Royal Navy did not keep individual service records on ratings before 1853, nor did it maintain comprehensive registers of personnel, so records before 1853 are particularly patchy."
So it doesn't look like the admission form is likely. But have a read through that Guide to see if there's anything that you haven't tried yet. Some of those things, like Allotment Registers, we have found, unless I'm getting mixed up with another case. Maybe you should print it off and tick off the bits that you've done.
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