Sig P320 80% Frame Rail Calculator
In doing the Sig P320 80% Build I had to do some math to cut the frame rails down to size. Yes, the top plate of the jig got me close but I still needed to remove some additional metal. I created this calculator to help me with the math based on my measurements to fine-tune the rail size based off of a factory Sig Fire Control Unit.
Learn More
We have the most complete coverage of the P320 80% build process on the Internet. Make sure you visit our P320 80% Frame Completion, P320 80% Parts Kit Install and P320 80% Range Testing videos. Also, visit our P320 80% Build Adventure article to read about the problems that we ran into during this build.
Our videos and articles will help you complete this build and show you some of the areas that can be problematic. The P320 80% build is not hard to complete and we consider it an intermediate skill project.
If you would like to know more about the tools that we used on the Sig P320 videos visit https://trb.fyi/tools-used-in-the-p320-disassembly-and-reassembly-videos and visit our troubleshooting guides at https://trb.fyi/troubleshooting/ while you are at our page.
Other P320 Videos that are not 80% builds
If you are not interested in building the P320 80% pistol but would like to know more about this firearm, visit our P320 Field Strip, Slide Disassembly, Slide Reassembly, FCU Disassembly/reassembly, as well as our Fire Control Unit Removal and Grip Module videos.
P320 80% Frame Rail Calculator – How to use
To use this calculator measure your front and rear slide rails after you have trimmed them down to the size if the top plate and plug them into the highlighted area of the calculator and it will calculate how much you need to remove from the frame rails.
Choose which frame rail to file down and trim it to that size. For instance, Side 1 Front Rail measurement after material removal, this can be either the Front Right or Front Left. Trim that rail until you reach the measurement below before moving to the other rail.
These measurements may not get you exactly to the size you need but will allow you to get close enough to do some final tweaking to match your slide.
 | |||||
| Front Rail Measurement 80% Frame | Front Rail Measurement Sig Frame | Total to remove on 80% Front Rails | Total to remove each side of 80% Front Rails | Side 1 Front Rail measurement after material removal | Side 2 Front Rail measurement after material removal |
| 0.8921 | 0.857 | 0.0351 | 0.0176 | 0.8745 | 0.857 |
| Rear Rail Measurement 80% Frame | Rear Rail Measurement Sig Frame | Total to remove on 80% Rear Rails | Total to remove each side of 80% Rear Rails | Side 1 Rear Rail measurement after material removal | Side 2 Rear Rail measurement after material removal |
| 0.8855 | 0.8595 | 0.0260 | 0.0130 | 0.8725 | 0.8595 |
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