For anyone thinking about undertaking the Sig P320 80% I wanted to document the required tools and and steps required to complete the JSD Supply 80% insert. The insert and jig to complete are available directly from JSD as well as F &F Firearms, as well as others I am sure.
-Deadblow hammer or mallet
-Drill Bits: 9mm, 3mm, #22, #39, #40, 7/32 (these should come with the jig)
-Misc files (small flat file and needle file at a minimum)
-Dremel with small diamond tip and cutoff wheels
-Benchvise (not required but makes it much easier)
-Drill Press (not required but makes it much easier)
Here is how the JSD P320 80% insert starts:
I will try and go step by step to keep the process simple. You can click on any of the pictures to enlarge them for a better view.
1. Insert 80% insert into the Jig. Make sure that the insert is sitting below the tabs on the jig. These tabs make sure that the insert stays put during the drilling and bending operations.
2. Pre-bend the tab down so that they’re started before inserting the top half of the jig. According to JSD this step may not be required, but it was simple and could save a lot of frustration or galling of the jig later. One end of the upper portion of the jig is beveled to start the rails bending. A few light taps with the hammer is all it takes.
3. Insert the top half of the jig and then either hammer it down until the rails are bent as far as they will go, or I found that if you turn the jig sideways you can use the vice to actually compress the two jig pieces together and bend the tabs. Using the vice or a hydraulic press was by far the easiest and most controlled way of bending the rails. One thing I noticed though is that the rails do not bend completely, granted the factory sig P320 inserts don’t appear to have the rails exactly horizontal either. After completing a couple of frames different ways, I found that tapping the rails down so that just sit above the jig yielded better results in the final product, ie less play in the slide. A couple of light taps with a brass hammer or bunch is all it takes.
4. After the rails are bent, there will be excess length in the rails that needs to be trimmed. To trim the rails, a hacksaw worked really well. Utilizing the top of the jig as the guide you simply cut down until the excess part of the tabs is removed, careful to cut evenly to avoid cutting down into the jig. Other options for cutting were brainstormed such as dremel with cutoff wheel, or even using files, but it seemed like both of those options would likely result in jig damage. The hacksaw worked really well and took all of 5 minutes to complete.
5. After the rails are trimmed using the jig, you should measure the rail width against the frame. I found that the after cutting the jig left the rails slightly oversized still (likely due to the hacksaw not cutting clean straight down). Using a flat file I carefully took additional material off the rails until the rail width is .002″ or so smaller than the slide. You will need to be careful here though and make sure equal amounts of materials are taken off each side in order to keep the slide centered, and not cause issues with the ejector. After the rails are filed to the correct width, all rail edges should be broke to remove any sharp edges. That includes the top, bottom, front, and back. A few light strokes with a fine flat file or stone should be sufficient. Please see below for a picture of a factory Sig P320 insert to see how the rails look from the factory. The factory insert is on the left, the 80% insert is on the right.
6. Drill the holes. As you can see in the jig pictures, the holes are all clearly marked with the required bit size. There were a total of 9 holes to drill and using a drill press took about 10 minutes. Take note that two of the #40 holes do not go all the way through. They eventually will be combined into a single notch for the Takedown Safey Lever to go through. All other holes go through both sides. If using a drill press you can drill the holes through from one side.
7. The takedown safety lever notch needs to be completed. In order to do this you cut out the area between the two #40 holes noted earlier. I used a Dremel with a diamond bit (7144) to cut this piece out. After using the Dremel to knock out the small piece of metal between the #40 holes, I used a small needle file to clean up the slot.
Link to the dremel bit: https://www.homedepot.com/p/Dremel-3-32-in-Diamond-Wheel-Taper-Point-Rotary-Bit-for-Wood-Jade-Ceramic-Glass-Hardened-Steel-and-Semi-Precious-Stones-7144/202263212?MERCH=REC-_-PIPHorizontal2_rr-_-203362654-_-202263212-_-N
It’s worth noting that in my experience these bits only last through one insert maybe 2 at the most. If you have multiple inserts to complete you may want to pick up a couple.
8. It is recommended that after the holes are drilled, you go back over the holes with a flat file to remove burrs which may cause difficulty with installation of the FCU components. I experienced that there were large burrs left after drilling even using brand new sharp bits. The frame should feel flat and smooth around the holes after you file and clean them up. If there are burrs on the outside of the insert, it will be difficult to insert in the grip module.
9.Trigger Pocket cut: The 7/32″ hole drilled on the right side of the insert will need to be cut to allow for passage of the trigger through it. The jig shows this required notch and can be used as a guide. To cut, I used a hacksaw (carefully since you are only cutting the notch on one side, the right side) and then used a file to get it to the final dimensions. Due to space constraints a needle file, or small triangle file will likely be needed.
As a reminder again, ONLY CUT THE RIGHT SIDE. If you cut both sides you will have an issue with the slide catch.
10. If using gen 2, post-recall parts, you will need to cut off the tab in front of the right rear rail.
To tell if you have post upgrade parts, you can look at the Safety Lever. You have pre-upgrade parts if it looks like this:
I’m sure there are other indicators, but these are the ways that I found to identify the difference.
And that’s it folks. After completion you can assemble the fire control unit, and assemble the grip and slide.