 Some, such as the Heckler & Koch VP70, will only fire in semi-automatic when the stock is removed because the select-fire mechanism is incorporated into the stock.The VP70 also introduced a three-round-burst limiter to improve controllability.The Beretta 93R not only uses a detachable shoulder stock and a three-round-burst limiter, but also a folding forward hand-grip to improve controllability in full auto.