On sale at the Lawrenceville, Ga., Gun Show last weekend, one such bump-fire device is known to shake poorly built rifles apart from the racket they make. A video accompanying the small metal trigger device showed an assault-style rifle pumping out dozens of rounds in seconds. It retailed for $49.95.
To be sure, the ATF has been paying close attention to the devices, and have delineated a narrow line of legality based, in essence, on mechanics versus physics.
Assault-style weapons can't be mechanically customized to spray-fire, but a nonmechanical device that simply aids the shooter's own firing action remains on this side of legal, according to ATF.
In 2005, the ATF rescinded a "letter of legality" given to one such device, the Akins Accelerator, mostly because the actual product didn't match the model sent to the ATF for approval.
But the problem also arose from a mechanical spring used in the original Akins. The product, springless, is now on sale again, certified by ATF.
Reviewing Mr. Cottle's Slide Fire, a Guns America blogger noted last year, "There isn’t going to be any way to get around what this thing does and I think it is best to call it what it is," he writes. "The Slide Fire is a $369 replacement stock for your AR-15 that when used properly, simulates automatic fire."
“The Slide Fire simply allows you to shoot as fast as you want to,” Cottle told Guns America. “You can shoot one round, 2 rounds, 3 rounds, 15 rounds or a full magazine.… There are no moving parts in the Slide Fire and no springs. You hold your finger on the trigger rest and push forward to fire the gun. It is not automatic. Nothing is automatic. You actively fire every round, and if you stop pushing forward or you take your finger off the trigger the gun stops firing. It just helps you fire the gun in semi-automatic very fast."
So far, for gun owners, the bump-fire devices are largely regarded as cool toys, and salesmen were cutting prices on the devices at the Lawrenceville Gun Show in order to move them.