The most common error here is the result of changing the buffer tube and or spring. For instance, if you change from a collapsible carbine stock to a precision adjustable stock, you may need to change your buffer tube and or spring as well. This is a very common issue we see as folks typically prefer a different stock due to the recoil of the .458 SOCOM when upgrading a 5.56 rifle. Remember, if it’s too strong or too weak, it may not be able to push the round into the chamber thus causing a failure to feed.