12 Gauge 2X Stack Undershot Insert

Sometimes with the CB1138 (the WAA12R clone) you will have a wad failure with 2X5 stack of buckshot. This is because a the payload is pushed back under acceleration as all of the payload weight is on the bottom two pellets. Sometimes a pellet breaks thru the bottom of the wad and only 9 pellets group. Some wads are so distorted by this that they do not like they ever were wads. Assuming the base seal is destroyed velocity will dramatically suffer.

The idea behind these inserts is that the stack height is unaffected and that the second row of pellets from the bottom have a “shelf” to stand on so that when fired four pellets are more evenly supported on the surface of the wad. If your wad has a flat round bottom, there is a good chance these will fit. These will not fit in say an RXP12 wad,: rounded bottom. This insert is designed specifically for the CB1138 wad.

Printed with PETG HF, 0.2mm standard setting, 100% infil. PLA work, but PETG is said to be more temperature stable. My application is .32, but .33 will likely fit.

There are 5 heights of inserts, the first is the basic design, the others add height, the “(0.XXX”)”. I liked the “0.050””, second from the bottom row of pellets just touching the top of the insert, taller seemed to have them sitting on the top of the insert (slightly effecting stack height), lower sitting on the bottom row of the pellets. Somewhat, when fired the column of pellets is crushed, I just want to insure the insert helps in the support of the four bottom pellets as best possible.

I’ve done this before with PLA and RXP12 wads, and others and it worked well, 2X5, 23gr Unique, fairly tame but wads would fail all the time. But to work with that wad the insert ends up being fairy complex and fragile to fit well.

For me, this is just an economy plinking load, but what if it is the King Zombie? Crap! Ten pellets, ten pellet, ten...