SIG Sauer P320 .40 S&W, .357 SIG Magazine, 18-Round


An 18-round extended magazine for the SIG Sauer® P320 chambered in .40 S&W or .357 SIG. The magazine may differ slightly from the image pictured. These are original OEM magazines.

State and regional magazine capacity restrictions apply. Therefore, we cannot ship this item to California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Maryland, Massachusetts, New Jersey, New York, Rhode Island, Vermont, Washington, Washington, D.C. and Cook County in Illinois.
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This OEM SIG Sauer P320 18-round magazine is for use with the .40 S&W or .357 SIG cartridge.

P320 18-Round Magazine Features

  • 18-round capacity
  • Works with .40 S&W or .357 SIG ammunition
  • High-lubricity finish for reliable function
  • Removable sleeved base plate for enhanced comfort and function
  • Rear witness holes in increments of five to display the remaining rounds in the magazine
  • Removable base plate for easy maintenance
  • High-tensile spring for unmatched reliability and service life
  • Durable polymer follower
  • Complete steel body construction

Images may differ slightly from the actual product. These SIG Sauer high-quality magazines are sourced from multiple manufacturers and made to SIG’s exact specifications. Because of this, there may be slight differences in stamping and finish color.

18-Round Magazine Fit Guide

  • Fits P320 models chambered in .40 S&W or .357 SIG
  • It also fits the SIG P250, chambered in .40 S&W or .357 SIG

The 18-round extended magazine will fit all P320 models, including those with XSeries grip modules with or without the magwell installed.

Additional information

Weight N/A
Dimensions N/A


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Many parts sold by Grayguns - including but not limited to triggers, trigger kits, internal components and spring kits - are intended for installation by a qualified armorer or gunsmith who is familiar with the firearm.

Although kits fit with no issues in a great majority of pistols, Grayguns cannot guarantee perfect functionality in every instance.

Due to varying tolerances present in all mass-produced firearms, professional fitting by a qualified armorer who is familiar with the pistol's action may be required.

Grayguns offers installation services for all parts kits we offer. If you have any issues or questions about the installation process, STOP IMMEDIATELY and contact the Grayguns Customer Service Team.