So just a quick update.. After looking a little closer to why a pistol mag wouldn't fit into my G3 T97 I was able to figure out what the issue was
I tried a CPD (c products) Lar-15 mag and I was able to get it to go however it was extremely tight. So much so, I had to use a vice to pull out the mag. I examined the marking on the mag and inside the mag well and was able to determine the root of the problem. The spine of the mag is out of spec and rubs against the "rails" in the magwell. Using my vice I applied pressure to the sides of the spine to get it back to spec and now it's smooth as butter
Some tips..
1. Don't apply to much pressure to the spine. The amount you need to adjust is not measurable by the human eye or a measuring tape. It's probably a 1mm adjustment from both sides
2. Go slow.. Squeeze, try to insert into magwell and if it's still tight repeat.
3. Let the base plate hang out on one end to avoid any damage to it
4. Apply downward pressure with the palm of your hand as you tighten the vice, this will ensure it doesn't pop-out and pressure is evenly applied.
hope this helps!