Crown area: Not good enough. You really want to see deep down into it if you can. CVA makes those little battery bore lights. Or they did once? Maybe check around for one. EBay is a good start. Might be able to catch a "Buy it now auction" on one. Oh almost forgot those lights came in different color luminances. Yellow / lime green is the best for checking a barrels bore with.
"Do not follow where the path leads, rather go where there is no path and leave a trail for others to follow."