I have a PSA PA10 but might want to upgrade barrels. It's reasonable to see the crush washer as a one-use item. It might not be, but if it were, I wouldn't be surprised. I understand the bolt isn't necessarily going to head space properly with a new barrel, particularly with an AR-10, so a new bolt might be necessary. The rest of the BCG would likely be fine I suspect, unless the bolt or gas rings just don't fit.
My current barrel has an adjustable gas block I really like, so as long as the diameter is the same, I figure it's reusable too. As long as the new barrel's gas system is the same, the gas tube should still work as far as I know. I'm just getting into upper building, so I don't know what sorts of things are of limited use. The other thing is AR-10s are not as universal as 15s. Changing brands could cause some issues, so caution is warranted.