Need some quick advice please

I have a brew in the boil pot right now. OG is SUPPOSED to be 1.039 +- I have a 7 gallon preboil and I am at 1.040 already before boiling down. I posted earlier about my mash tun not being great.. I made a new one today and the same recipe I have done twice has a much higher OG than the previous 2. Can a mash tun make THAT much difference, and is there anything I can or should do?

I feel some designs may be more forgiving with various brewing methods. Some might just require a certain finesse.

You may want to start taking your pre boil SG (temperature adusted) and use it to figure out your brewhouse efficiency. If your equipment and methodolgy remains constant, you can use your efficiency number vs the one you see in a recipe to adjust grain amounts so that it comes out the same. Or you can just "live" with having higher numbers.

This is driving me crazy. I swear I cooled the preboil wort down to 70. And it was 1.040.......... I collected MAYBE an extra half gallon of wort and added that in during the boil hoping to up the volume to hit the OG. Put 5.5 gallons in the primary(what the recipe was calculated at) and hit 1.040 dead on at 70 degrees(1.039 expected). That is twice now that the preboil and post boil gravity did not make sense.

Perhaps your 1st runnings and sparge runnings weren't well mixed? Since the sparge runnings are less dense, you'd get a lower gravity measurement if you took the sample from the top. The boil would equalize things.