Cylinder exit holes

[crabo]

I ordered a lap kit, book, and push through slugs yesterday.  I am wondering about opening up the cylinder holes.  I assume you would want to do this before you start firelapping.    How far do I go with this?  Just so the bullet I use will push through with minimal resistance?  (I am sure it will tell me all of this in the book, but I am wondering)

Thanks

[Veral]

The book was written a couple years before I developed the push through slugs, so doesn't describe their use.
However they come with very detailed instructions.

In brief.  Open cylinder throats if necessary till they are at least .001 larger than barrel groove diameter at the largest point.  Lapping will increase the largest diameter only a few 100 thousandths of an inch.
You can order a mold from LBT based on slug diamethers, or even send me the slugs for measuring, and I'll cut the mold to what your gun will need after alpping.  You can lap with bullets from that mold, or another mold you have on hand if it casts bullets large enough to fit your guns needs.