Originally the barrel of the Ross Mark III was 30.5 inches and very heavy.

If you take one apart, you will notice that the action, apart from the actual lockup area, is very lightweight construction; all the weight of the rifle was in that barrel.

Most of the PLYmouth RMLI rifles in circulation have had their barrels cut back to 24 or 26 inches. This would DEFINITELY upset the original vibration pattern.

Hope this helps.