Just a heads up to anyone interested in using a BlueForceGear Redi-Mod on their WE - the mags will not seat correctly :(

The feed-lips of the WE mags hit the top of of the magazine housing and won't allow for the mag to fully seat and lock in place.

The only solution I see is cutting out a little "window" in the top of the magazine housing - but this would expose bbs and the mags feed-lip, negating a major positive aspect of the Redi-Mag -
which is keeping your magazine protected from the elements, dirt and overall damage.

It's running with an O-Ring in place, and it doesn't take too much force to tighten it even more, so I should be okay.

if my memory serves me right the WE AR platforms guns can use the following real steel parts without any additional modifications:

Buffer tube
Selector switch
Grip
Magpul ASAP sling loop and other similar things
RIS (?)
Bolt catch
Mag catch
Buffer tube spring and the buffer (not sure what it's called sorry)
Upper receiver
Charging handle

Just want to see if I am missing from my list. Any input is greatly appriciated. Im looking to upgrade my T91 with some real steel M4 parts :)

Some of your list is correct, but some isn't

You will need to modify the following if you want it to work correctly with a WE:

Selector switch ( I believe you have to modify the selector plate for it to work properly , Upper reciever (the trigger box needs to be cut down to allow for a RS upper to fit, the charging handle, and a real bolt catch wont work as the WE bolt catch is different from a RS bolt catch. You can use a RS buffer spring, but I don't know if your bolt will lock back, you probably wont get a full mag off and your cool down with be the worst.

A note on a few of the items you suggested for your WE.

Selector switch, no mods but most are semi auto only, if you use one, your WE will be limited to that only. You can purchase an auto/semi safety but you will need to modify your sear and auto sear.

Mag release, because the top of the WE mags are flat and not contoured like a real magazine, you will have to press the mag release to insert a magazine. Otherwise you need to grind or machine down some material off the mag release.

Upper Receiver, mechbox needs to be machined down, hop-up chamber 3 and 9 O'clock tabs needs to be shaved off.

Charging Handle, Eh, depends on brand, USGI/standard charging handles will probably need to have a pin inserted into it to properly grab the bolt carrier. I would pin the bolt carrier, a cheaper part. Ultor/BCM grabs the bolt with no problems.

Bolt catch, completely different design.

I need to replace my hopup rubber, any suggestions on where to get a replacement or sizings?

Just talk to frank at toronto airsoft, he usually has some canabolized guns that he can sell parts out of, that or jugglez may sell some of the AWSS hop ups still

Yeah, I should call them, it's probably about time I stuck in the RA-Tech upgrades as well, my gun is stock with the exception of that NPAS

Yea, I know that the stinger hop up that came with my Ratech up grade kit isnt supposed to be that good.. if you are looking to upgrade the hop up unit and inner barrel at the same time, apparently the falcon unit is supposed to be pretty good, I have no idea where to get it though... I keep my stinger rubber as a back up just in case though.

Open bolt I assume? If it is, VSR rubbers will work. I'm currently using a Firefly soft rubber.

Is the WE PDW ambi selector switch compatible with WE M4. Any know or have tried? Everywhere I look and ambi selector for WE m4 platforms are sold out. Only by looks I am gonna guess it is compatible. Correct me if I'm wrong here folks.

Tried it, it does work, but the PDW lower is thicker and the levers awkwardly sticks 2mm out each side.

You'd assume wrong, I got my WETTI way before the open bolts came out, and I have no interest in switching over to the Open Bolt system

Dammit. I guess I'll keep looking....
Not even airsoft global or ROSV has them. I might be SOL :(

You can always get the TSC ambi safety.

http://shop.ehobbyasia.com/t-s-c-amb...bb-series.html