Mossberg 500 12 Gauge Shell Saddle

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Mossberg 500 Shell Saddle You can purchase these for $57 at Mesa Tactical or you can print your own. Mossberg 500 6 shell carrier with integrated rubber tubing (similar to Mesa design) that keeps the shot shells in place either brass up or brass down. I’m including the Fusion 360 files because you may want to adjust the tightness of the tubes before printing. I’ve provided detailed instructions for this but you’ll need Fusion 360 (available for free on their site). I tested the tubes for tightness in cold weather by putting a test print with 00 buck shell in the freezer. Shells didn’t come out, but your results may vary based on printer, filament, etc. So to help you out I have included two (optional) test prints you can do before you print your own. Print out the HoleSeparationTest.stl test print, thin edge on build plate and bolt hole faces parallel to the build surface. Use this print and a small square (optional) to check the alignment of the trigger pin hole and ejector screw hole. If they are off, you’ll have to adjust the hole separation dimensions on the fusion 360 saddle component, BackPlate sketch. Print out the ShellHldrTest.stl (top of saddle to build plate when slicing). This is a print of one shell holder with critical features. The saddle will take about 6-7 hours to print so the test print might be worth it. Use this print to test several things: 1) Nut recess fit for the #8 and #10 machine screws. Screw hole size. Adjust as needed for your preferred nuts on the BackPlate sketch for the saddle (not the test print). 2) Tubing fit. Note you may need to use a rat tail file and/or a 5mm rod to clear the tube of stray filaments. The top of the tube holes at each opening tend to sag into the space. Alternatively you can use supports selectively (when slicing) where the tube holes open up to the shell tubes. 3) If you have time, leave a shot shell installed with rubber tubing in place over night. This tubing has memory so shells will loosen with time. Be sure you adjust the tube hole positions accordingly based shells being in place overnight. My preferred setting is already set in the Fusion360 file. Adjusting tube tightness before printing saddle 1) In Fusion 360, in the Mossberg500Saddle component, go to the SideTubes sketch and open it. 2) Open the picture TubeAdjustment.jpg in the downloads to see field d321. 3) Field d321 is a calculation based on shell holder and tube diameters. The value at the end can be adjusted (typically increments of 0.01 inches) to tighten (increase the parameter) or loosen (decrease the parameter) the shot shell fit. I prefer a setting of 0.07 as seen in the jpeg. You can alter the value and see the tube holes adjust to the left and right, thereby adjusting the amount the tubes extend into the shell holder space. Additional Materials Required: 1) #10-32 1-3/4” machine screw. I use the expensive option of the #10-32 1-3/4 in. Stainless Hex Button-Head Cap Screws from Home Depot due to the low profile and easily torquing hex head. (Sub a #10-24 coarse thread if you need to, philips head is least expensive). 2) #10 nut I used a #10 stainless nylock nut also from Home Depot 3) #8-32 5/8” machine screw with regular nut. Again, I went with the Home Depot stainless hex button head. You’ll need to modify this screw! See directions, below. 4) 3/16” OD micro fuel line/rubber tubing. Find a hardware store that sells this by the foot as you only need about 1 foot (2 sections cut to 142 mm or 5-19/32”). Picture is in the downloads for reference. Print the saddle top facing build plate for best results. Post Processing: 1) Unload the shotgun. Did I need to tell you that? 2) Check screw holes for fit against shotgun receiver. 3) After printing the saddle and two plugs, I take some emery paper to the inside of the tubes to remove strings and imperfections. 4) Note that shotgun shells installed BEFORE installing tubes will simply fall out. The fuel line tubes keep the shells in place, just like in the Mesa Tactical design. 5) Clean the tubing holes using the methods described above. 6) Use some emery paper or a file on the plugs as well as where they will install in the tube holes. They fit rather tightly so glue is not necessary, but both surfaces must be deburred. 7) Cut and install fuel line tubes and test shells for fit. 8) Install plugs using some force. 9) Remove trigger pin and ejector screw from shotgun. 10) Measure height of #8 screw head and threads. You’ll need to grind/sand/file the top of the head down to around 0.06” and the total screw thread length to about 0.55 to 0.6”. This is the low cost option rather than trying to purchase a low profile socket head screw (you can purchase this type of $crew at McMaster Carr if you insist on perfection$). The choice of button head is already low profile compared to pan head, so only a small amount of grinding is needed. 11) Install the #10 1-3/4 screw into the trigger pin hole. It will chatter a bit going in as it rubs against the pin retaining detent. 12) Apply Loctite where you are not using nylock nuts. 13) Attach the saddle and #10 nut and tighten, but not all the way. 14) Install #8 nut inside the saddle. Screw the #8 screw from the inside of the receiver. DO NOT TIGHTEN because the receiver is threaded, and the screw must catch both the receiver and the nut threads together. 15) Now align the saddle, push down on the #8 nut, and continue screwing until the screw catches the saddle’s #8 nut. DO NOT FORCE THE SCREW as you may strip the receiver threads! This might take several attempts. Once the screw catches the nut, tighten everything down. Remember the Loctite! 16) Now Rock & Roll!