Originally Posted by
kyratshooter
If you are scrapping a .223 upper for the .300BO you can use the same bolt, bolt carrier, extractors...
Personally, I would want to have both calibers available, so I would want a dedicated upper unit for each.
There are a lot of people slapping uppers together and getting away with it, for a while, but the barrel really needs to be head-spaced to the bolt, and most kitchen table builders can not do that properly.
Just like with any modern bolt action rifle, this is a high pressure round and head-spacing does matter. Most people would not even pretend to screw a barrel into a model 700 action and shoot it without proper head-spacing, but they feel they can slap a few AR parts together and call it a safe build. Just because it locks up, ejects, and the firing pin works does not mean it is safe.
As you cruise the internet you can find all sorts of blow ups that these people are claiming expose junk parts and bad manufacturing of parts, when the real problem is a bad build with sloppy tolerances and no attempt at head-spacing.