Just make it cosmetically better.
Check it out:

The manufacturers of the popular AR-15 rifle have made some slight cosmetic changes that have made the gun legal in New York state. The actual firing power of the gun has not changed, but the gun no longer includes a pistol grip and now resembles “an odd paintball gun.” The modified gun also lacks a bayonet lug.

At least one gun shop has received a letter from state police saying that the new AR-15 style rifles should be legal in the state as long as they don’t have some of the features that the law prohibits.

The new gun law bans all kinds of semi-automatic rifles that have been labeled with the “assault” term even though these are very common rifles and are no more powerful than the average hunting rifle.