[Bill Murphy]

A pocket size wall thickness gauge would only measure the barrel for a length as long as your pocket. The Manson wall thickness gauge, sold by Brownell's is more than a foot long, works well, and is as cheap as any gauge that does what it does. About a hundred bucks, will more than pay for itself with the first gun you measure with it. More expensive alternatives, less portable, are Tony Galazan's bench mounted gauge and Jon Hosford's set which is a bit more convenient than Tony's for use outside of the home and shop.