For those moving the 783's to a Chassis or other DBM to use a AICS pattern mag, understand that the action opening is one of the very few sized to fit the AICS mag pattern properly... and includes many custom actions.
The ramp angles, and other dimensions of the bolt/chamber/boreline could not be more perfect for feeding out of AICS mags. Big reason why I continue to run this action in mag fed competitions.
If you have a feeding issue, check that the action is sitting properly in the chassis/stock and that the mag is presented properly to the action. Doesn't always fit properly and will need slight tweaks.
If the rd is not being picked up, push up on the mag until it bottoms on the action.... that is correct, the mag WILL bottom on the action at the right height for function. If there is a bunch of upward movement, the mag latch is too short for that mag used. When properly fitted, the mag latch will lock with a few thou of vertical play so you can remove the mag easily.
If the bolt hits the case but the bullet nose dives, you have a mag issue and/or the mag is tilted in the mag well. With a DBM, you need to raise the front of the unit. With a chassis, check the inletting and how the action sits in the chassis.... .likely will need manf intervention.
If running steel mags, try opening the front lips a bit more so the bullet tip is more elevated as viewed from the side. Could be a follower issue as well????
that will get you started. The 783 is one of the very few factory actions designed to run with AICS and AW mags. I wonder what long term plans big green has for this action?????
Good luck.
Jerry