can an sbr ar-15 be registered as multi caliber?

[Hawkeye]

Originally Posted by ar15dave

I was told by BATFE that you can only put one caliber in section 4c of the Form 4 and list additional calibers in section 4h of the Form 4 along with any engraving wording and other additional information about the item being registered/transferred.

That is correct, for the time of registration.

However, you are perfectly able to change the caliber to whatever you want after it is registered. The ATF "requests" that you notify them of any permanent (read, you can no longer or no longer have the parts to return it to the registered configuration) alterations to the configuration of the SBR, but there is no legal requirement to do so.