I just purchased a SP-1 lower and was wondering is this a good preban lower?  Also if I can legally install a M-4 16" upper and collapsable stock? Someone who has any advice or opinion please respond.  
Thanks!

According to a recent BATF letter ruling, if you purchased the lower either stripped or without an upper receiver, it has lost it's 922(v)(2) exemption and is no longer a "preban" because, as a lower-only, it cannot qualify as an assault weapon under 921(a)(30).  If it isn't an assault weapon, it can't have a 922(v)(2) exemption.  Assembly into 921(a)(30) configuration, or even back into SP-1 configuration would be illegal.  That's the BATF opinion on the subject.

If it is marked "Colt AR-15," it should retain it's 922(v)(2) exemption even as a stripped lower.  

All Colt SP-1's are marked "Colt AR15"

Hence, they retain their legal grandfathered assault weapon status by name, regardles of how they are transferred.  It does not matter if it was transferred stripped if it is a Colt AR15 marked weapon, according to the code.

All SP-1's are preban (made before 1994 and sold as complete rifles) as well.

And yes, you can legally install a M4 16" OAL upper and collapsible stock.  Of course, you will probably need a conversion pin if you are installing a new upper receiver, as it will most likely be a small hole design.

I am looking for the source of this ruling:

"According to a recent BATF letter ruling, if you purchased the lower either stripped or without an upper receiver, it has lost it's 922(v)(2) exemption and is no longer a "preban" because, as a lower-only, it cannot qualify as an assault weapon under 921(a)(30). If it isn't an assault weapon, it can't have a 922(v)(2) exemption. Assembly into 921(a)(30) configuration, or even back into SP-1 configuration would be illegal. That's the BATF opinion on the subject."


I am looking for a link to or a location where i can view a copy of this ruling.  Although I am familliar with the laws which apply to semiautomatic assault weapons, I have never seen the source for this in formation.

Thanks,

Rob

Thanks Shadowblade, I was wondering why I couldn't find the authority for it, now I see its more of an advisory than a rule.  I wonder how the Bureau of Arbitrary Technical Findings came to its conclusion?

I have the letter right here on my desk.  It's a letter ruling from the Chief of the Firearms Technology Branch and constitutes the BATF's opinion on the subject at the time that it was written.  It appears to be a straight-forward, strict interpretation of the law as it is written.  I personally believe that Congress intended the law to mean "once an AW, always an AW," but that's not the way they enacted it.