I would put a post on the armed forces board about the military details that you have for James Snook and ask whether anyone could do a look up in the regimental muster rolls for you at The National Archives or could recommend a researcher.
A look up in the muster rolls may not give you sufficient details and a researcher may be able to find other information in other military records at TNA, for instance if James bought himself out of the army there would be more information, but a look up in the muster rolls would at least be a start.
You need to be as specific as you can about dates for your request, because the musters are quarterly books detailing the names of the men in the regiment and their pay. So to follow a man for a year you have to order four separate books. They will tell you nothing about a man's background. Only the quarter where he leaves the regiment or where he enlists might give you further information. If you can give a specific date for him leaving the regiment you can request a look up in that muster quarter (that one hopefully would also give a date for his enlistment, so then that quarter can be checked). Even if the musters reveal nothing more than when James enlisted if that was pre the date of the 1851 census that would eliminate the James born Buckland Ripers.
Since there are military experts answering posts on the armed forces board (and some who aren't) they may also be able to give you further advice or be able to tell you further information about James' regiment. If they are able to give further information, please post the link onto this thread so we can all read the information you are given as it may further inform searches in Dorset records for you.
I am not sure what you mean by is Buckland Ripers the closest to Weymouth. Closest in comparison to what other place/s?
Put Buckland Ripers into Google maps and then click the
- (minus) button twice to pan further out. You can then compare the distance for yourself, bearing in mind Weymouth will have grown a little since 1851. On the 1851 census James was in nearby Broadwey which is also shown on the map.
Google maps (in its get directions section) states (on modern roads and not as the crow flies) Buckland Ripers is 5 miles away from the central point of Weymouth (which won't have changed since 1851) and that today it would normally take about 12 minutes to get between the two points.
http://maps.google.co.uk/maps?hl=en&ie=UTF-8&rlz=1T4HPEA_en-GBGB236GB236&tab=wlThere are death registrations for James Snooks in Dorset after 1851. Since the age on death in the index doesn't start until the 1860s it is difficult to know whether any of those death registrations could be for James Snook born Buckland Ripers, so no mention of this man after the 1851 census doesn't necessarily mean that he is your James Snook. It just means he disappears after 1851 in the English censuses either because he has died, emigrated, changed his name etc.
Regards
Valda