As a follow-up, I should note that there are many reasons why you may not find a pension file for a Revolutionary War ancestor. Pensions were initially granted to veterans, their widows or their orphans, only on the basis of death or disability while in service, or because of a minimum length of service. Most of those records were destroyed in an 1800 fire, and more in an 1814 fire. Congress, in a series of acts in later years, expanded the number of veterans eligible for pensions. The most liberal of those was the act of 1832 which authorized pensions for all who could demonstrate at least six months of service, regardless of need. Most of the extant pension files that I have read are either earlier applications based on need or disability, and describing the financial condition or disability of the veteran, or later applications under the act of 1832. Applications under the act of 1832 represent only that small percentage of veterans and their widows who had survived to a very advanced age.
As it turns out, there are undoubtedly more documents in the pension files than what I have. The full series of Revolutionary War pension files microfilms is publication M804, whereas what I have is from publication M805 which contains selected records.
The best descriptions of National Archives microfilm series are found in booklets published by NARA describing those series, which are downloadable in PDF format. The way I have been accessing them is a bit convoluted - if anyone knows of an easier way please let me know. To access those booklets you will probably need to use Internet Explorer, as Firefox does not work correctly on that part of the NARA site. You will need to know the publication number, such as M804 or M805 for the pension files, or, say, M432 for 1850 census returns. Go to:
and click the "Use Our Microfilm Search" button, and on the next page the "Advanced Search" link to the right of the search button. Enter the publication number in that field, then click the search button. Now select any of the publication titles and the next page will have a link to the PDF booklet describing that publication. The descriptions vary by publication - those for the pension records provide an excellent overview of those files, while those for a census merely list the enumeration districts on each roll of film.