In July 2006 I contacted Roger Hancox, Proof Master at Birmingham and asked for a comparison of 850 bar and 3 1/4 tons per square inch. The reply I received was detailed but beyond my comprehension. Perhaps someone with an advanced degree in maths and/or engineering could come with a practical comparison chart, so that so that we ordinary people can be confident That we are selecting shells that develope pressures suitable for safe use in our English guns. Mr, Hancox E mail address is ACVOKE@aol.com.

PS. Here are the conversion factors that apply:
1UK. long ton =2240 pounds. 3 1/4 tons per square inch =7280
1 Bar =14.50377 p.s.i.

As you may have already guessed a strict mathematical comparisons is not applicable.

Roy Hebbes