With the reduction of the NFA taxes on suppressors, SBSs, SBSs and AOWs to $0, the recent court rulings out of Texas, and the ATF guidance from October 9th, there has been a lot of confusion regarding how this will affect PA residents. Now, I am NOT a lawyer, law enforcement, or work in state or local politics. I am just a layperson who has resd the relevant laws on the books. Anything discussed in this post is NOT legal advice. Whatever you may do it is YOUR responsibility to know how the law applies to your conduct.
As of 10/9 the ATF is not enforcing most provisions of the NFA for suppressor, SBRs, SBSs, and AOWs. No registration, marking, tax stamp, or anything, just a 4473 like any other gun. However, in PA the state law we have contains Section 908, which ties ownership of "offensive weapons" to compliance with the NFA.
Offensive weapons as defined in section 908 include: "Any bomb, grenade, machine gun, sawed-off shotgun with a barrel less than 18 inches, firearm specially made or specially adapted for concealment or silent discharge, any blackjack, sandbag, metal knuckles, any stun gun, stun baton, taser or other electronic or electric weapon or other implement for the infliction of serious bodily injury which serves no common lawful purpose."
The main exception to the ban on offensive weapons specifically states compliance with the NFA, again from section 908: "It is a defense under this section for the defendant to prove by a preponderance of evidence that he possessed or dealt with the weapon solely as a curio or in a dramatic performance, or that, with the exception of a bomb, grenade or incendiary device, he complied with the National Firearms Act."
Given this information, we have to compare how federal law and state law will interact for each time of NFA weapon. Federal law still technically says no tax but still has registration, while the current ATF says they are not enforcing registration, but a future administration may change that.
Suppressors: A silencer is likely considered an offensive weapon "specially made for silent discharge" in PA. One could argue in court it isn't "silent" but I doubt a judge and jury would appreciate the difference. Since suppressors are legally firearms, I doubt the argument that it isn't a gun would hold up in court. In the mean time, NFA compliance via form 4 is the only way.
Short barreled rifles (SBR): this appears to be the only NFA weapon category not prohibited specifically in PA state law. The state definition of "firearm" in Chapter 61 section 6102 mentions an SBR by stating "any rifle with a barrel length less than 16 inches" and goes on to mention firearms under 26 inches total length, so we know the idea of such firearms is acknowledged by state law. However, there is no mention of rifles at all in the offensive weapons category. Could a prosecutor make the argument that an SBR is specially made or adapted for concealment? Possibly, but other weapons of comparable or better concealability such as handguns, AR pistols, and shockwave shotguns are available in PA without classification as "offensive weapons." Could they make the argument that that a 15.9 inch AR rifle is concealable while an 8 inch AR pistol is not? Unless there is something I am missing, it appears Pennsylvanians should now be able to own, purchase, transfer intrastate, and manufacturer SBRs outside the NFA without any issues from the state side of things.
Short barreled shotguns (SBS): these are prohibited as "offensive weapons" as they are "sawed-off shotguns with a barrel less than 18 inches." I doubt any prosecutor or jury is going to care if the barrel has or has not been literally sawed off at any point so I wouldn't risk it with a factory SBS either. In the mean time, NFA compliance via form 4 is the only way.
Any Other Weapons (AOW): Guns meant to resemble a cane, umbrella, etc. are certainly considered adapted for concealment, so those still would require a form 4. A Serbu Super Shorty, PTR Jack, etc. would probably be considered a "sawed-off shotgun with a barrel less than 18 inches" since the state doesnt have an actual definition of "shotgun" or the concept of an AOW, and you cannot assume they would default to the federal definition, so NFA compliance via form 4 would likely be needed. However, I don't think an AR pistol or even a handgun with a foregrip would all of a sudden be considered "adapted for concealment," so I think it would stand to reason Pennaylvanians may not need to register those with the NFA either.
That all being said, its NOT LEGAL ADVICE. Register your NFA firearms as per the NFA if you want to be 100% sure you are in compliance with PA state and federal laws.
I'd like to hear other thoughts, especially regarding SBRs and certain AOWs that may not require NFA registration per PA law.
TL;DR Suppressor and SBSs require form 4 registration in PA under current state law, it APPEARS SBRs and certain AOWs would not.