UK Working Standards recomended minimum wall thickness measured 18" from the barrel breech from Double Gun Classics p. 56, Vol. 1, No. 4 Jan-Feb, 2006:
2 1/2" 12g - .028
2 3/4" 12g - .032
Re-proof recomended minimum - .024
The Hunter's Encyclopedia - from the German proof house: minimal wall thickness at the end of chamber, regardless of length, for 12, 16 & 20 gauge guns should be 2.3mm (.0906") for 'Ordinary Good Steel' or 2.1mm (.0827") if a 'Special Steel' was used.
For the 24 & 28 gauges, due to their higher pressures, 2.4mm (.0945") was recommended.
Minimal wall of .6mm (.0236") was recomended in the "forward third" of the barrel.
Last edited by Drew Hause; 01/12/11 08:21 PM.
