One of the accomplishments of the system was solid cast cannons bored to precise tolerances which allowed the walls to be thinner than cannons poured with hollow cores , but because cores were often off center the wall thickness determined the size of the bore .
One of the accomplishments of the system was solid cast cannons were bored to precise tolerances , which allowed the walls to be thinner than cannons poured with hollow cores . 
 However , because cores were often off center , the wall thickness determined the size of the bore .