This came out of a long discussion at M14 Firing Line Public Forum about why some barrels are more accurate than others and why some lengths (even in the same caliber) just never seem to equal another length. Basically it started out (I believe) as a question about the lesser accuracy of the SOCOM type M1A rifles vs. the longer barreled rifles.
I thought about what was being passed back and forth by the various contributors to the the thread (several of them knowledgeable M14/M1 match armorers) and came up with this. When I posted it no one disagreed and some stated it pretty accurately described what was going on (vibration wise vs. accuracy) as barrel length changed. While some folks will say shorter barrles are stiffer than longer barrels the trick is to have the muzzle at the same spot each time the bullet leaves the muzzle.