Once my stuff is up to temp I don't have trouble filling a brass mold up to 700gr bullets. They are flat point and hollow point for 50cal.
The lee pot has no adjustment for flow.
I also found my 10 pound Lee pot leaked no matter what I did
Didn't see if you had the venting rectified. But! Older Saeco moulds only had vent grooves on one half of the mould block. From what I have seen for responses, "most " have been good. Casting is and should be fun! Start with clean alloy, And yes Range scrap is just fine. If you are focusing on 32 full wad cutters both pressure and velocity are going to relatively low, preheat your mould ( I use a Canuck Rubber ) hotplate run your alloy just hot enough that it takes a couple of seconds for the sprue puddle to solidify. When you are at casting temp with both the alloy and mould a gloved hand is all that is needed to open the sprue plate. When pouring , allow the alloy to hit the side of the sprue plate opening and flow into the cavity, that should help if you think there is a venting issue. A little tin added is always a benefit for mould fill out( BUT) with too much tin and heat when your pot is full you can end up with finning or wiskers from the part line or vent lines. As mentioned casting doesn't just happen ! It is trying sometimes and it s best just to walk away!!! Any mistakes made are easily erased and re attempted till the perfect silver pills start dropping from the mould.You may have hit on the problem. I compared my Seaco mold with another one that I have and there are no grooves on one side of the mold. It looks like someone sanded the surface down, removing the grooves.
After looking up this mold on yahoo, it definetly should have grooves on both sides.