Post-ban semi-auto rifle with detachable magazine + collapsible stock (evil feature #1) + pistol grip (evil feature #2) = it's an "assault weapon" in NYS and a violation of NYS AWB to possess. Sorry. Here's the text of the relevant part of the statute (NY Penal Law section 265.00 - Definitions):
22. "Assault weapon" means (a) a semiautomatic rifle that has an
ability to accept a detachable magazine and has at least two of the
following characteristics:
(i) a folding or telescoping stock;
(ii) a pistol grip that protrudes conspicuously beneath the action of
the weapon;
(iii) a bayonet mount;
(iv) a flash suppressor or threaded barrel designed to accommodate a
flash suppressor;
(v) a grenade launcher; or
(b) a semiautomatic shotgun that has at least two of the following
characteristics:
(i) a folding or telescoping stock;
(ii) a pistol grip that protrudes conspicuously beneath the action of
the weapon;
(iii) a fixed magazine capacity in excess of five rounds;
(iv) an ability to accept a detachable magazine; or
(c) a semiautomatic pistol that has an ability to accept a detachable
magazine and has at least two of the following characteristics:
(i) an ammunition magazine that attaches to the pistol outside of the
pistol grip;
(ii) a threaded barrel capable of accepting a barrel extender, flash
suppressor, forward handgrip, or silencer;
(iii) a shroud that is attached to, or partially or completely
encircles, the barrel and that permits the shooter to hold the firearm
with the nontrigger hand without being burned;
(iv) a manufactured weight of fifty ounces or more when the pistol is
unloaded;
(v) a semiautomatic version of an automatic rifle, shotgun or firearm;
or
(d) any of the weapons, or functioning frames or receivers of such
weapons, or copies or duplicates of such weapons, in any caliber, known
as:
(i) Norinco, Mitchell, and Poly Technologies Avtomat Kalashnikovs (all
models);
(ii) Action Arms Israeli Military Industries UZI and Galil;
(iii) Beretta Ar70 (SC-70);
(iv) Colt AR-15;
(v) Fabrique National FN/FAL, FN/LAR, and FNC;
(vi) SWD M-10, M-11, M-11/9, and M-12;
(vii) Steyr AUG;
(viii) INTRATEC TEC-9, TEC-DC9 and TEC-22; and
(ix) revolving cylinder shotguns, such as (or similar to) the Street
Sweeper and Striker 12;
(e) provided, however, that such term does not include: (i) any rifle,
shotgun or pistol that (A) is manually operated by bolt, pump, lever or
slide action; (B) has been rendered permanently inoperable; or (C) is an
antique firearm as defined in 18 U.S.C. 921(a)(16);
(ii) a semiautomatic rifle that cannot accept a detachable magazine
that holds more than five rounds of ammunition;
(iii) a semiautomatic shotgun that cannot hold more than five rounds
of ammunition in a fixed or detachable magazine;
(iv) a rifle, shotgun or pistol, or a replica or a duplicate thereof,
specified in Appendix A to section 922 of 18 U.S.C. as such weapon was
manufactured on October first, nineteen hundred ninety-three. The mere
fact that a weapon is not listed in Appendix A shall not be construed to
mean that such weapon is an assault weapon; or
(v) a semiautomatic rifle, a semiautomatic shotgun or a semiautomatic
pistol or any of the weapons defined in paragraph (d) of this
subdivision lawfully possessed prior to September fourteenth, nineteen
hundred ninety-four.
If you have the stock permanently pinned at a particular length, so that it is no longer collapsible, then the stock is no longer an evil feature.
Of course, if your receiver was made pre-ban (9/14/94), then you are free to customize the rifle as you see fit.