I'm about to build a pump mag. What do I need to know?

[Nobody]

The one thing to remember is that, when the pump breaks (99% pump breakages are in the wave spring), you end up with a semi. Albeit a Lvl7 mag, but a semi none-the-less.

Thanks TK! Even when you fail, you still give us a better than most gun.

[luke]

But the tolerances are so tight that bending it into the exact right shape is very difficult.

Then you're doing it wrong, because it's actually very simple.

[Walking Stick]

OP, maybe this will help you in getting the angle and length correct.

[luke]

Just assemble the marker without the body and you can see exactly how much to bend the rod.