Click here if you are having trouble viewing the gallery and video on your mobile device.

var _ndnq = _ndnq || []; _ndnq.push([’embed’]);

For the second time in less than a month, San Francisco 49ers star linebacker Reuben Foster has been arrested, this time on suspected offenses of domestic violence, threats and possession of an assault weapon. The incident played out early Sunday at a Los Gatos residence.

So what kind of weapon was it?

According to an archived police dispatch radio recording of the 911 call, “the RP (reporting party, apparently Foster’s longtime girlfriend, whom he is alleged to have assaulted) advises there should be at least two AR-15 weapons in the house.”

But multiple sources familiar with the investigation told this news organization that police found a single SIG Sauer 516 short-barreled rifle, or SBR. Foster, who was released Sunday after posting $75,000 bail, was booked on a single count of possession of an assault weapon.

The 516 is a relatively new model based on the AR-15, the civilian version of an M16. According to the gunmaker’s website, “the tactical world is full of ARs. But only a select few are tough enough and accurate enough to be called a SIG. The SIG516 is the natural evolution of the platform, with a host of enhancements designed to survive anything, anywhere.”

And there’s more from firearms maker Sig Sauer that would titillate any hard-core aficionado of semi-automatic weapons: “An adjustable gas valve allows operators to increase the flow of gas when using lower pressure ammunition or when adverse conditions require additional energy,” says the weapon’s description. “Reduced flow and the off-position enhance the use of suppressors. Barrels feature an A2 flash suppressor and are threaded 1/2×28 TPI, allowing the SIG516 to adapt to a number of aftermarket accessories and suppressor mounts.”

You can pick one up for $1,799 at sigsauerguns.com.

So is a 516 legal in California? It depends. While the 516 does not appear on the list of illegal AR-15 variants at the California Department of Justice website, that would be because it’s a recent release (the list hasn’t been updated in more than a decade; the 516 has been produced since 2010). State law also includes generic characteristics that make a gun illegal — if it has the capacity to accept a detachable ammunition magazine and at least one of a list of military-style characteristics including, for example, “a pistol grip that protrudes conspicuously beneath the action of the weapon.”

On the sigtalk forum, there’s a discussion about how a Sig Sauer can be modified to make it legal in California — removing the grip is one such modification. Other weapons manufacturers looking to sell in Cailfornia used to outfit semiautomatic rifles with a “bullet button” which requires a special button to be depressed — fittingly, by the tip of a rifle round — to release the clip, to meet the state’s fixed-magazine requirement. But that workaround was outlawed last year by the state Legislature.

By the way, that flash suppressor that the Sig Sauer website raves about apparently would also have to be removed in California.

Here’s a video overview of the 516:

Here’s a YouTube video showing how a 516 can be modified:

And here are some views of the 516 in action: