SBR Full auto?

[fightingquaker13]

Yikes! Great info guys! Still, another reason for me not to own full auto. I mean price aside, it just seems like there are WAY too many potential land mines there for me. If you're comfortable with it, I wish you luck. Still, it seems like you better have a good lawyer's phone number and the green to pay him. You don't need to be convicted, just prosecuted and it seems things can get pretty pricy and exciting in a hurry. It ain't right, but it seems to me that in any endeavor where an entire governmental agency seriously doesn't want you to do something and the burden of proof is on you, with vaguely worded laws and rules; the reward better be worth the risks. Here? I'm not so sure.  
FQ13 who will stick with semis, but is glad that other people aren't. I wish you well.

[Magoo]

I've been wondering about this for awhile. Can you own a rifle that is both short barreled and full auto or is this illegal under the NFA? Just as a for instance I’m talking about submachine gun or a personal defense rifle?

1st. things first. Everything depends on more information than what you provided. 
Some States outlaw SBR & SBS. What State are you in?.
A Firearm that is Registered as a Machinegun is not under any restrictions as to Barrel lengths. Lets say you have a HK "Registered Sear".
It is by itself an "NFA Registered Machinegun." If you put it into any HK Rifle with a Full Auto Carrier, the Barrel length can be under the 16" Federal Requirement until you remove the "Registered Sear." Once The NFA Item is removed from it's Host firearm, the Host now has to follow the Reg's. If you wish to retain the Short Barrel on the firearm, before the Registered Item is removed, you would complete 2 "Form 1's" to Register the Firearm as a "Short Barreled Rifle". You send in 2 Completed Form 1's Filled out along with 2 Finger Print Cards and a Cert. of Compliance, along with a Check for $200.00 made out to the BATFE. Once the Approved Form returns, you will then be required to engrave your Information onto the Firearm as required and will then be "Legally" able to remove the "Registered Sear" from your Now Registered Short Barreld Rifle Host with no problems. It sounds complicated, but it isn't.
If you need help, let me know and I'll do what I can.