The good news - my SBR just came back in..yaye

The bad news, the only mags it will seat are the aluminum 40 rounders. The steel HK, 20/30, Promag and MKE's will not seat. Ive tried every solution.. bringing the shelf block down a bit , modding the mags a bit.. everything.  I pulled the mag catch tab out and it looks super worn and rounded. Ive concluded that i should try ordering a brand new GERMAN mag catch assembly from HK Parts (20 bucks). Anyone had this issue?

Thanks - It sucks because i really like the platform =(

I have a hk53 clone.  The Hk 40 rd mags fit fine, the MKE needed a little bit of filing to fit, and the pro mags fit just fine...  All of them function 100%.  Rumor is that magpul will have some avail soon too...

Not even metal hks fit, must be something with the mag catch tab

Tried all the mag fitting to no avail

Correction, Aluminum 40rd mags do fit fine in mine. I'd guess its a mag catch issue?  On my mke mags, I had to file the ledge on the mag that fits flush with the mag well. I did not adjust the mag catch on the mag itself.

You may have too much bottom length on the mag well itself. Check against a known in-spec receiver if possible. You can use lipstick to mark (rubs off) the contact points. If it looks like the bottom of the mag well is preventing them from inserting all the way, use a big bench stone or a file to take some off and make/keep it square. Compare the angle of the bottom of the mag well to the mags' external stop tabs when the catch slot is parallel to the bore axis to keep that angle correct. (I know that last part sounds crazy without a picture.)

Thanks