Quote Originally Posted by RCCrawler View Post
If this is true why do they ask for specific barrel lengths and specific calibers?
Don't shoot the messenger, it's the ATF's rules. You have to list the configuration that you're making, you can't just make a generic SBR lower (no matter how much sense that would make). As someone mentioned, keep the original upper around, otherwise it's a permanent change which isn't a big deal, you just have to file paperwork declaring the change.

O2