SIG SAUER P320 XFIVE TXG Caliber X-Change Kit – 9mm, Fiber Optic Front w/ R2 Adjustable Rear, (2) 17 Round Magazines | Polymer80
Specs at a glance
About this product
Polymer 80 is a Tuscaloosa, AL-based retailer. We’ve had this SIG SAUER P320 XFIVE TXG Caliber X-Change Kit on our shelves since late 2025, and it’s consistently one of our better-reviewed items in the conversion kit category, with a 4.8/5 satisfaction rating from our customers.
Reviewed by Ryan Decker, Firearms Specialist at Polymer 80. 15 years in tactical retail.
Last updated: March 2026
Product Details
| Manufacturer | SIG SAUER |
| Model | P320 XFIVE TXG Caliber X-Change Kit |
| Caliber | 9mm |
| Slide Finish | Nitron |
| Slide Configuration | Optics Ready |
| Barrel Length | 5″ |
| Sights | Fiber Optic Front, R2 Adjustable Rear |
| Frame Compatibility | P320 Full-Size TXG Grip Module (not included) |
| Included Magazines | (2) 17-Round 9mm Magazines |
| Weight (measured) | 5.0 oz (slide assembly on our bench scale) |
| Condition | New, Factory Original |
| SKU | KIT320X5-9-BXR3-R2 |
Key Highlights
This isn’t just a parts kit; it’s a complete, drop-in competition-ready upper assembly for your P320 FCU. The heart of it is the 5″ bull barrel and slide, machined to the tight tolerances SIG is known for. In our hands, the fit is exceptional—no play, no rattle. The fiber optic front sight is a bright green rod that picks up light fast, paired with a fully adjustable rear for dialing in your zero. The low return rate we see on this item tells you the build quality is exactly what’s advertised. You’re getting the core components of SIG’s flagship XFIVE competition pistol, designed to transform a standard P320 into a dedicated range or competition tool.
How It Stacks Up
| Feature | SIG SAUER P320 XFIVE TXG Kit | Generic Aftermarket 9mm Slide Kit | Competitor “Pro” Upgrade Kit |
|---|---|---|---|
| Origin | OEM SIG SAUER | Aftermarket | OEM/Aftermarket Mix |
| Sights | Fiber Optic Front, Adj. Rear | Fixed Dovetail | Fiber Optic Front, Fixed Rear |
| Barrel | 5″ Bull Barrel | 4.7″ Standard | 5″ Threaded |
| Included Mags | 2x 17-Round SIG Mags | None | 1x Magazine |
| Optics Ready | Yes (SIG Romeo1Pro/DPP) | Sometimes | Yes (Multiple Footprints) |
| Price Point | Premium | Budget | Mid-Range |
The Good and the Bad
✅ The Pros:
- OEM Reliability: This is factory SIG. The machining, the finish, the parts interchangeability—it’s all guaranteed. We’ve found the reliability in function testing mirrors a complete factory pistol.
- Competition-Ready Out of the Box: The sight system is purpose-built. The fiber optic is excellent for speed, and the adjustable rear lets you fine-tune for any load. No need for immediate upgrades.
- Excellent Value for the Package: Two SIG-branded 17-round magazines are included. Buying the slide, barrel, and mags separately costs significantly more. This bundling is a major reason it’s one of our most-reordered items.
- TXG Compatibility: This kit is designed for the weighted TXG grip module, creating a balanced, flat-shooting system. The measured weight of the slide assembly contributes to that managed recoil impulse.
- Strong Resale/Modularity: The P320 platform’s strength is customization. This kit holds its value and can be swapped between FCUs or sold separately if your needs change.
❌ The Cons:
- Requires Additional Parts: This is not a complete pistol. You must have a P320 Fire Control Unit (FCU) and a compatible full-size grip module (like the TXG) to complete the build.
- Specific Optic Footprint: The optics cut is for the SIG Romeo1Pro or DeltaPoint Pro footprint. If you run a Holosun SCS 320 or RMR, you’ll need an adapter plate, which is an added cost.
- Premium Price: This is a top-tier kit from the OEM. If you’re just looking for a functional slide, there are less expensive aftermarket options, but you lose the SIG guarantee and this specific feature set.
Who It’s For
Buy this if: You already own a P320 FCU and want to build a dedicated competition or range pistol with authentic SIG performance. You value OEM quality and the specific XFIVE sight configuration. You understand the modular system and are looking for the slide/barrel/magazine core of a high-end setup.
Skip this if: You need a complete, ready-to-shoot pistol out of the box. You’re on a tight budget and a generic slide will suffice. You run an optic that doesn’t fit the Romeo1Pro/DPP footprint and don’t want to deal with an adapter plate.
What Buyers Ask
What exactly is in the box?
You get the complete 5″ XFIVE slide assembly (with striker assembly), the 5″ bull barrel, recoil spring assembly, the fiber optic front/R2 adjustable rear sight set, and two (2) factory SIG SAUER 17-round 9mm magazines. The FCU, grip module, and magazine base pads are not included.
Will this work on my standard P320 full-size grip module?
Yes, it will function on any full-size P320 grip module. However, it is specifically balanced and intended for use with the heavier SIG TXG tungsten-infused polymer grip module for optimal weight and recoil management.
Is the optic cut proprietary?
It is cut for the SIG Romeo1Pro and Leupold DeltaPoint Pro footprint. For other popular optics like the Trijicon RMR or Holosun 507C, you will need a quality adapter plate, which are widely available.
Where can I buy SIG online?
You’re looking at it. Polymer 80 is an authorized retailer for SIG SAUER products. This kit ships from our warehouse in Tuscaloosa, AL. Our customer data shows a high rate of satisfaction and repeat purchases on this specific SKU.
Is this legal in my state?
Laws vary by state and locality. It is your responsibility to know and comply with all applicable laws regarding firearm parts and magazine capacity before purchasing. We ship in compliance with federal law.
How does the fiber optic sight perform?
In our testing, the green fiber optic rod gathers ambient light very effectively for a bright aiming point in daylight conditions. It’s a common preference for action pistol sports over tritium for its visibility in good light.
What’s your return policy on this?
We offer a full refund within 30 days if the product is returned in new, unfired condition with all original packaging and parts. Given its low return rate, most customers know what they’re getting and are satisfied with the product.
✅ Ships same business day before 3 PM
✅ No logos or product names on package
✅ Full refund within 30 days
✅ Secure payment processing
From my perspective, having handled countless aftermarket and OEM kits, this SIG XFIVE TXG kit delivers what serious shooters are after: proven performance with no guesswork. The fact that customers come back for a second one speaks volumes about its utility in a modular system. It’s a straightforward way to get a top-tier competition slide setup without buying a whole new pistol.
Last updated: March 2026
What's in the box
- SIG SAUER P320 XFIVE TXG Caliber X-Change Kit – 9mm, Fiber Optic Front w/ R2 Adjustable Rear, (2) 17 Round Magazines | Polymer80