CREATE TABLE table_29159 ("Chambering" TEXT, "P1 diameter  ( mm ) " TEXT, "A external  ( cm 2  ) " TEXT, "P max  (  bar  ) " FLOAT, "F bolt  (  kgf  ) " FLOAT, "F bolt" TEXT)

What is the p1 diameter (mm) when .300 lapua magnum is the chambering?
SELECT "P1 diameter (mm)" FROM table_29159 WHERE "Chambering" = '.300 Lapua Magnum'
SELECT "P1 diameter (mm)" FROM "table_29159" WHERE "Chambering" = '.300 Lapua Magnum'