JSD Supply P320 Insert Completion

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.



Tools Needed:
-JSD Jig
-Deadblow hammer or mallet
-Drill Bits: 9mm, 3mm, #9, #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
-Drill Press

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 punch is all it takes.


The image below shows how the rails should look after bending them more as noted above with a punch or hammer. If you don’t bend the rails flush as shown below it could result in excess slide movement (vertically) when the trigger is pressed. Please take care to ensure the rails are bent beyond what the jig will do alone.

4. After the rails are bent, we need to trim the excess length from the rails. With the top if the jig inserted, use it as a guide for hacksaw and slow cut excess rails off. I recommend using a hacksaw, although you can scribe the lines and use a dremel with a cutoff wheel later. You only want to cut deep enough so that the excess rail length pops off, don’t keep cutting down into the jig.

If you use a hacksaw, after time the jig will show wear on the tops of the sides, this is superficial and won’t effect function. I know of a jig that has at least 30 inserts completed this way and it is still total functional.


5. Drill the holes. When drilling the holes, make sure that the top of the jig is inserted and that the whole assembly is squeezed tightly by the vice to keep the insert locked down. As you can see in the jig pictures above, 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 Take-down Safety Lever to go through. Drill all the holes from one side and then flip the jig over and drill all of the holes from the other side. Do not try and drill the holes all the way through from one side.

When you remove the top of the jig after drilling, you may see holes in it where the drills hit it, don’t worry about those, they are superficial, and I have seen a jig after repeated holes where you could see through the top insert.

A couple of notes:

  1. You MUST use cutting oil. It lubricates and cools the bit. Smoke should not be coming out of the hole you are drilling! Use cutting fluid liberally for all of the holes. You can’t use too much, but if you don’t use enough the drill bits will dull quickly.
  2. Peck drill the holes. This means drilling a short distance then backing the drill out part way to clear the chip from the hole. So drilling in and out until the hole is complete. Don’t just try and drill the hole all in one motion.
  3. Let the tool do the work. If you have to use a lot of pressure to drill the hole, something is wrong. The bit is binding somewhere or more likely is worn out and needs to be replaced. You should apply light even pressure though to make sure the tool cuts.
  4. Use a drill speed of about a 1,000 RPM, if your drill press has slower speeds about 750 RPM would work even better.

6. Remove the insert from the jig and trim the rails, you should measure the rail width against the frame. In my experiences a little more width had to be trimmed off to fit the slide. 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.

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 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.

Cleaning and De-burring the holes. After drilling all of the pin holes will need to be de-burred in order to allow the pins to fit easily. A tool like this works really well for that, or can use the bits and run them through by hand. Also, you will need to file the inside of the insert to clean up the rough edges on all of the holes to make sure the internal components will fit and not get hung up.


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.

11. If you have one of the first production runs of the JSD insert you will likely need to file the rear of the insert to allow the safety to fully depress. The images below show the the area in red that you will need to follow. The insert on the right in the first picture is a factory sig insert that you can see the area that needs to be notched. After filing it is important to make sure that the safety lever depressed completely as shown in the image  below. If it doesn’t see where it is hitting and file more.

And that’s it folks. After completion you can assemble the fire control unit, and assemble the grip and slide.

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