I sincerely hope the .025" to .030" MWT given for the forcing cone are gets corrected, or better yet, deleted entirely so nobody finds this Thread and gets the wrong idea.
For good quality fluid steel barrels, .090" is a safe conservative minimum for 12 gauge. 16 and 20 gauge guns and loads often operate at slightly higher pressures, so something like .095" minimum for the beginning of the forcing cones would be better.
That .025"to .030" MWT figure given for the forcing cone area is flat out wrong! .030" is about twice the thickness of a paper matchbook cover... and it's crazy to think that is a safe MWT for the forcing cone area. .025" would be a good minimum for the thinnest part of the barrels at roughly 9" behind the muzzles. Pressures are much lower at that point in the barrels. When you get down in the .020" or thinner range at the end of the barrels, they become much more susceptible to dents, or bulges and splits from very minor obstructions such as snow.
This is not to say you won't find guns with barrels a bit thinner than .090" at the beginning of the forcing cones. But many of those guns were proofed at pressures much lower than modern SAAMI or CIP standards. You may get away with shooting a gun that has a wall thickness of .075"to .080" or thereabouts, but you aren't leaving much of a margin of safety. Especially if using standard pressure loads.
It seems to me that if Mark can do Free Tagline Advertising in every post he makes here, he could have also posted his page of CIP minimums here for the benefit of everyone. He is another of the Free Tagline Advertisers who refuses to say whether he is paying Dave the $12.00 fee for each and every sale resulting from that Free Advertising of a For-Profit Business venture. I'd think any advertiser who is playing by the rules would be happy to say if they are paying the fee. I suppose it would be different if one had something to hide or be ashamed of.
