Does anyone know if I can replace a pinned NYS compliant version stock with a different kind? I am thinking I should be able to as long as I repin it in place correct? Also if I choose to shorten the legnth a little I should be able to, as long as its in a fixed position correct?
THanks

NY State gun law:

Miscellaneous:

It shall be unlawful to possess any "assault weapon" or a "large capacity ammunition feeding device". So called "assault weapons" lawfully possessed prior to September 14, 1994 and "large capacity ammunition feeding devices" manufactured prior to such date are grandfathered. A license shall not be issued for a handgun defined as an "assault weapon." Any person lawfully in possession of a firearm, rifle or shotgun who suffers the loss or theft of said weapon shall within twenty-four hours of the discovery of the loss or theft report the facts and circumstances of the loss or theft to a police department or sheriff's office. It is a crime to possess any rifle, shotgun or handgun in or upon the building or grounds of any school, college or university in the state without the written permission of the institution. It is a crime to possess a fake or imitation handgun with intent to use it unlawfully. It is a crime to intentionally point any firearm toward another person (except in self defense), even if no malice is involved. It is a crime to deface or alter the serial number or any other distinguishing number or identification mark on any handgun. Possession of any handgun that has been defaced creates a legal presumption that the possessor committed the offense. The presence of a firearm in a vehicle is presumptive evidence of its possession by all persons occupying the vehicle except if: the firearm is found upon the person of one of the occupants; the firearm is found in a vehicle operated for hire by a duly licensed driver, then the presumption will not apply to the driver, or the firearm found is a handgun and one of the occupants has in his possession a valid license to have and carry concealed. Note: In this digest, the word "firearm" is used in its general sense, i.e., any rifle, shotgun, or handgun. However, readers of the New York law should be aware that the term "firearm," when it appears in the text of the statutes, has a special meaning, being applied only to handguns and other firearms "of a size which may be concealed upon the person."

An "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 non-trigger 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 ****mat 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 Streetsweeper 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 1, 1993. 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 14, 1994.

"Large capacity ammunition feeding device" means a magazine, belt, drum, feed strip, or similar device, manufactured after September 13, 1994, that has a capacity of, or that can be readily restored or converted to accept, more than ten rounds of ammunition; provided, however, that such term does not include an attached tubular device designed to accept, and capable of operating only with, .22 caliber rimfire ammunition.

Source: Firearm Laws for New York