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P320 - Barrel Measurements

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One of the most asked questions on this part of the Sig forum seems to be around barrel swaps. There is a very nice thread showing the C slide on a SC frame and vise-versa.

People have very different opinions about swapping barrels vs using a x-change kit. Comments vary from Sr. Mix-a-lot to bring out your dead. Just to be transparent, I'm in the Sr. Mix-a-lot camp.

I got out my digital calipers and took some measurements.

My digital calipers is a Milutoyo Model CD-6" set to mm and zeroed with jaws together.

My measurements in mm include:
  1. OD near breech
  2. OD near muzzle
  3. width across breech

Below are my findings.
  • Sub-Compact 40sw: 1-14.45, 2-14.49, 3-16.63
  • Sub-Compact 9mm: 1-13.95, 2-13.98, 3-16.65
  • Compact 40sw: 1-14.45, 2-14.49, 3-16.65
  • Compact 357sig: 1-14.47, 2-14.49, 3-16.67
  • Compact 9mm Threaded: 1-13.95, 2-13.99, 3-16.64

I am making no statements of what this data means or doesn't mean. I'm simply providing the data for others to draw their conclusions about how to use the investment they have made or are about to make.

Attached are some pics to go along with the above data.
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604 Posts
Discussion Starter · #5 · (Edited)
I've been mulling this over and over. I have a P320c in .357 SIG, along with a .40 barrel. I mainly shoot 9mm, so I've been on the fence on getting a 9mm barrel or an x-change kit. This helps a lot. Thanks for taking the time to put this together.
I did a write up on my 9mm barrel swap. Check out the below thread with how its working for me.

Overall I'm very happy with the barrel swap. I feel the 40/357sig recoil spring is a big heavy but my spring would still be considered 'new' and hasn't been broken in. Worst case I may bur a 9mm recoil spring. Even if I buy the spring, its still less than 1/2 the price of an x-change kit. All my mags (12 in total in various sizes) are 40/357sig and they work great with 9mm.
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