Snaplock 12GA Ammo Box + Expanding Tray

Updated version of my expanding ammo trays for 12GA Shotshells

… now with a Snaplock box for more secure transport. The original model can be found here. 

Multiple size options now available (2026/03/07 update):

In keeping with compatible box sizes for stackable storage, I've created some additional versions that fit the Medium and Large box footprint. To get a full box of 25 rounds, you'll have to use the Large box footprint which does not have the expanding trays. The Medium Box footprint will accommodate the expanding tray but is limited to 18 rounds.

Box Stackability Matrix

Box Size	Calibers	Round Count	Expanding Tray
Small	9 mm 5.7 x 28 mm 380 auto 357 Magnum 38 Special .223/5.56 300 BLK	50
Small	22 Long Rifle	98
Medium	45 acp 44 Magnum 40 S&W 10 mm 6.5 Creedmoor 6.5 x 55 Swedish 8 mm Mauser 308 WIN 30-06 Springfield	50
Medium	20 GA	25
Large	12 GA	18
Large	12 GA	26 or 28
Large	338 Lapua 45-70 Govt 6.5 PRC	50
Double Wide	12 GA 20 GA	25
Double Wide	9 mm .223 / 5.56 / 300 BLK	100
Double Wide	22 Long Rifle	256 or 272

Design features:

• Store your ammo in a tight and compact package
• Expand the rows to get your fat fingers in there for easy extraction
• Trays are easily removable.
• Latches can be customized in the slicer with caliber and bullet weight text
• Inner label is larger allowing more text.
• Pouch behind inner label to store original manufacturer packaging like LOT numbers or load details.
• These Snaplock boxes will stack on top of the original boxes.

Stacking ring is optional if you don't need that feature. Or glue them in place on the bottoms:

The stacking rings are compatible with the small caliber boxes. Larger caliber boxes will not sit side-by-side.

Inner label lets you store original packaging details like Lot Numbers or powder charges.

I started with the parametric Snaplock V1 box originally created by @Hugo but have added my own improvements:

Lid height has been meticulously calculated to ensure bullet clearance when opening and closing. The lower height of the bottom and side cutouts make removing the inner trays much easier.

Assembling the hinge:

There is a groove on the underside of the hinge on the bottom half of each box. You slide the lid half hinge into those grooves to assemble the hinge. It can be a tight fit, but once you get it started just advance it a small bit on neach side until it drops into place. A piece of filament can then be inserted in the hole of the hinge to keep everything aligned.

Check out my other models in this collection:

Here is a look at all the stackable boxes together: