DIY: Convert Your SIG SAUER P320 Into an M17 With This One Weird Trick [VIDEO]

The SIG P320 is one of the most popular handguns on the planet. That’s due to a couple of factors. First is its modularity. Once you have a P320 fire control group, you can mix and match barrels, slides and grip modules of all sorts of designs and from dozens of makers to create exactly the pistol — or pistols — you want.

Second is the fact that the US Army chose the P320 as its standard issue duty firearm. That prompted military and law enforcement agencies around the world to adopt the M17 and M18 of one flavor or another as their designated duty guns, too.

Then, last year, SIG announced a new red dot sight, the ROMEO-M17, for use with the M17 and M18 pistols. The ROMEO-M17 is, it’s fair to say, overbuilt. It’s an enclosed, gas-purged design with a 2MOA dot, a 32 MOA circle (you can select one, the other, or both) and 15 brightnes settings including 3 that are night vision compatible. All that is packed inside a thick, low-slung 7075 aluminum housing that I suspect — but haven’t tested — you can actually drive a vehicle over.

It also has a two-dot tritium rear sight to replace the rear sight of the M17 or M18 that’s removed when you mount the ROMEO-M17. It co-witnesses on the lower third beautifully, so if your batter dies (its rated at 20,000 or continuous run time), you can still keep shooting accurately.

In short, this thing is built to stand up to the hardest use in the worst environments and keep on going.

While it’s not inexpensive — $799 MSRP — that kind of military grade build and toughness is obviously attractive to lots of gun owners. There’s just one problem. The ROMEO-M17 uses a proprietary mounting footprint designed to work with M17 and M18 pistols and it attaches to the slide from below.

In other words, if you don’t have an M17 or M18, you can’t attach a ROMEO-M17 red dot…as this graphic from SIG makes clear . . .

But if you’re already a P320 owner, you now have another option aside from buying a complete M17 or M18. SIG SAUER is selling full-length M17 slides with a ROMEO-M17 pre-mounted.

The slide comes fully equipped with barrel and spring so you just need a full-size frame…which I didn’t have when I got the upper.

That’s not a big deal if you’re a P320 owner as I was. I just bought myself a full-size grip module (in tactical peanut butter, of course), installed my fire control group, slid on the slide and I was ready to go (don’t forget you’ll also need a 17-round full-size magazine if, like me, you normally run your P320 as a compact).

A possible hiccup: SIG doesn’t always have the M17 slide/ROMEO-M17 combinations available. As you might imagine, they stay pretty busy fulfilling their contracts for the military. That means they don’t always have the slide/sight available for sale. In fact, they just took the option down from their sight in the last few weeks as all of their production is going to meet the demand from those military contracts.

But don’t worry, they’ll be back. The MSRP for the combination is $1099, which is a surprisingly good price when you consider you’re getting a complete slide with barrel and spring plus an $800 red dot. Keep your eye on the SIG SAUER sight if you’re interested and snag one when they’re back in stock.