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Enjoying Sig P320 Modularity

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We've played a bit with the P320 and P365 modularity. This recent build of a P320 was meant to see if I could tame the "compact" size of pistol the same way my P365XL build did for a magazine article. I didn't have a true "compact" (roughly 4" barrel and 15-round capacity) size of P320, but thanks the the modular system I didn't need to purchase a complete additional firearm. Just a grip module, slide, and barrel.

Taming: Without going to extremes I wanted to take advantage of the aftermarket to make this build shoot softer that other guns of the same size class. Perceived recoil can be countered in a number of ways. This attempt attacks felt recoil with four approaches:

  • Reduce reciprocating mass: Slow-motion footage of dozens of pistols firing has shown us that most of the felt recoil in a pistol comes not from the detonation of the round, but from the mass of the slide slamming fore and aft. The less mass we have in the slide, the less weight will be tossing to and fro with each shot. There is a fine line to this as the momentum of the slide moving forward is also what strips a round from the magazine and shoves it into the chamber. Between the rcoil spring and slide mass there needs to be enough energy to accomplish this. I don't have a facotry slide to compare against for total weight, but the L2D Combat slide certainly has more material removed than a standard slide and the fluting on the barrel can't hurt either.

  • Increase non-reciprocating mass: The weight below the slide acts as a shock absorber when it comes to recoil. The more weight the frame has, the ore it resists to being moved by the recoil impulse. This is why steel-framed guns shoot softer, and why brass brackstraps are popular among competition shooters. Another trick often employed by "influencers" is to mount a giant flashlight to the rail of the gun. This adds to total weight and at a leverage point to resist the pistol's effort to rotate in hand. The Icarus Precision aluminum grip module doesn't add a ton of weight, but does add some and accomplishes another goal.

  • Change Spring Rate: Over the years we've experiemented with a number of DPM Systems recoil assemblies. With some guns they didn't do much (regular P365 and AK) but on others they've had incredible effect (P365XL, Walther P99, AR15). So we found the right size for this slide length and gave it a try. The DPM System uses three springs that work to progressivley declerate the slide's rearward travel, and progressively accelerate the forward travel. In many cases it also prevents the slide from bottoming out against the frame; the biggest source of felt recoil and muzzle flip.

  • Enhance Ergonomics: What can't be mechanically enhanced can be manually. Friction between flesh and gun can help, but what helps the most is a good hand fit. Sorry there's no universal answer here, you just have to learn what works for your hands. For my hand this Icarus Precision. The double-undercut of the trigger guard has to be one of the most under-rated enhancements a pistol frame can have. It's likely only a milimeter or two, but by permitting the support hand to be higher on the gun control is greatly enhanced.


Once it was all together I could think of no better way to check functionality than the classic GBGuns Shooting Impressions format. Having performed this procedure on hundreds of pistols I already have a good mental baseline of what to expect. You can see this battery of experiences in the video below:

Ammunition seen in our Shooting Impressions video was made possible by our Patrons and supporters of our ammunition savings account through Ammo Squared.

Parts Used:

Fire Control Unit: This is legally the "firearm" of a Sig P320. We pulled this one from the P320 XCompact we reviewed previsously. If you're unfamiliar with the modularity, all one has to do is remove the slide stop lever and this module pops right out of a P320. From there you can swap to any grip module you'd like of the same or compatible saliber. It's a handy feature to be able to construct different build types without necessarily purchasing another "firearm". This also lets you start off with a basic model and upgrade over time. You can pull one from a P320 you already own, or purchase the fire control unit separately.

Slide: This beautiful piece is the Odysse from L2D Combat. I don't have a standard 3.9" Sig slide to weight this against, but as you can see there are significant weight reduction cuts on the front of the slide. The slide comes fully assembled with extra-tall (suppressor height or co-witness height) sights and is cut for an optic with the RMR footprint. The finish wore quicker than expected, so we're on our way to a "battle-worn" finish with touches of 17-4PH stainless steel peeking out from high spots. Machining in impeccable on this slide.

Sights are also from L2D Combat. Intended as a co-witness height for the RMR, they're very nicely constructed and produce a clean sight picture. If you do plan on co-witnessing you may want to consider selecting a color that contrasts your optic. Out of the box mine

hit slightly low and right. The verticle

may be height over bore, the horizontal is easy enough to adjust thanks to the Real Avid Sight Tool; it's nice to have finally found a good one.

Barrel: After the excellent experience I had years ago with an L2D Combat Glock barrel I was excited to give their Sig barrels a try. Accuraccy seems excellent, but for some reason this barrel tests lower in velocity than others. I don't know what's causing that, but calculated energy is still acceptable. I appreciate the fluting and cuts on the barrel hood for both style and possibly shaving a little weight (remember, this is a project about the end result, not one part miraculously changing the game). The friction marks from cycling are typical, but also serve as a visual reminder that this barrel makes less ocntact when cycling, and those flutes would be an egress path should any debris enter the slide. (<--this comment made for all the critics who fear getting into a grappling fight inside a grain silo and so fear slides with windows).

Spring: I've long been a fan of DPM Systems recoil assemblies. They use three springs to progressively decelerate the slide, often preventing it from bottoming out on the frame (where most of your perceived recoil comes from), then aggressively return the slide into battery. We've used DPM Systems products in AKs, ARs, and several pistols with varying degrees of success. It seems the improvement potential depends on the platform.

In the box are typically three different main springs so that you can tune the gun to run on the load of your choice, or to your shooting ability (yes folks, having a limp or slightly-limp wrist will cause problems if the spring is too stiff). I started off with the stiffest of the springs and made it through the What's For Dinner™ Test, so that's what I'll run with. Note that I have experienced a few wrong-item issues when ordering these, so cross check the part number with DPM System's own listings before purchasing. These won't make your gun look any cooler, but they can definitely change the shooting experience.

Grip Module: We've tried a few different grip modules and although hand fitment is a personal preference, there's also no arguing against the benefit of added weight. For me the Icarus Precision grip module simply fits best AND adds the non-reciprocating weight I was looking for. The double-undercut trigger guard also does wonders for getting the support hand higher for even better control of the pistol. These modules can be tough to find as it seems no matter how many Icarus Precision makes they're out of stock.

The Results: As with all things modified from what a team of well-funded engineers created, this home project may not be done yet. The pistol feel in hand like something of a totally different class of gun. I accomplished the goal of taming and already shootable platform into something very easy to shoot. I just need to figure out the low-right impacts and this will effectively become my cheater gun. Size and shape like a compact, handles like a race gun.

If you've tinkered with the P320 platform please let us know what you've tried and what the results were in the comment section below. If you've never tinkered I recommend starting with either the grip module or the recoil assembly as those two can give the most cost-effective improvements.

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Well done, sir! I’m not sure why there’s so much hate around P320’s. I own 4 and none have ever done me wrong and even have the added bonus of cycling everything I feed them, including my “chipper” practice handloads made with Missouri Bullets TEK-coated truncated cone lead bullets. Which, by the way, will not feed in my P-01, Agency and P80 Gen 3 clones. Note, they will also cycle in my P365XL, FM9 and VP9 (GASP, you ran lead through an HK? BLASPHEMER! Relax, it was just a quick test.). Anyway, 3 of the P320’s went back for refitting during The Great Drop-fire Scare of the mid-teens (which I now liken to Covid 19) and they came back, not…

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