You can use a large Crescent wrench, with a pipe extension for more torque. However, never force a barrel on a receiver, as this will distort the chamber. You should have the barrel shoulder cut down on a lathe, but if this is not possible, you can file it, but be very careful to get it even. Sears sells ($38) a 7 inch digital torpedo level with a LED readout, which is accurate down to 1/10 of a degree. You will need a barrel timing gauge , available from Brounells inc, item #093-200-010AD, $71.50.