The record for fastest shots is held by SX3. The FN SLP is essentially a SX2.
From the Winchester web site:
"Many of you know that the Winchester Super X® 3 Autoloader shotgun has proven to be the fastest cycling shotgun in the entire world. This shotgun has set records for speed in cycling, firing 12 shots in just 1.442 seconds."
From Multigun Media web site article "The Practical Shotgun and The Need For Speed" BY PATRICK E. KELLEY
"David (Neth) amazed the small gathering at a 3 gun match in
Winchester, Idaho by firing those five shots in 51
hundredths! The splits were three .13’s and one .12.
This gun(SX2) is full auto fast! By the way, this was with
Federal 00 buck. No, not the low recoil stuff, this was
Federal MAX 2 3/4 Classic."
From Chuck Hawks web site, article by Randy Wakeman
"Cycle rate is touted as important. A fast cycling shotgun is supposed to be good. Is it? Beretta Xtrema2 advertising spots show Tim Bradley firing 12 rounds out of an Extrema2 in 1.73 seconds. Tom Knapp shot a then world record with a factory Benelli M2 in 2004, breaking ten hand-thrown clays with ten shots in about 2.2 seconds. That record didn’t last for long, as on July 6, 2005, it was eleven clay targets hand thrown, individually shot, from the shoulder and without assistance with a Winchester SX3 by Patrick Flanigan. Patrick Flanigan cracks off 12 rounds with a Winchester SX3 in 1.442 seconds in another widely seen spot, clearly, quite a bit faster than the Xtrema2 managed. I’ve met Tom; he’s quite a gentleman and a fine spokesperson. I know Patrick, like him, and consider him a friend"
BTW, the new record did not last long as after Flannigan left Winchester for Mossberg, a new record was set as noted on the Winchester web site:
"CONGRATULATIONS RANIERO TESTA -- WATCH THE VIDEO HERE. With his Winchester Super X3 (SX3) autoloader shotgun, Raniero Testa succeeded in beating the world record by breaking 12 clay targets (thrown by the shooter with his right hand and shot individually)."