I had wanted to hold some of the good stuff for a future article, but realized there is a LONG way to go for a reasonably complete summary SO I went ahead and added what I have here
https://docs.google.com/document/d/1dnRLZgcuHfx7uFOHvHCUGnGFiLiset-DTTEK8OtPYVA/edit Many thanks to Dave Suponski, Ron Graham, Bro. Raimey and Bro. Walt for their contributions, and Adam W. Haskins, P. E., Metallurgist at Metals Engineering and Testing Laboratories, METL in Phoenix, Arizona.
If someone 'harvests' the information, an attribution would be nice, since some of the data cost me.
IN SUMMARY
what we know about pre-WWI guns and loads:
1. The gun makers said the guns were safe with the shells available in that period, the ‘rough forged tubes’ were proved in Belgium, and the finished gun was proved by the U.S. maker.
2. Smokeless powder shells were in no way “low pressure”:
20g 7/8 oz. 2 1/2 Dr. Eq. Bulk Smokeless pressure was 8000-9000 psi; 7/8 oz. 2 1/2 Dr. Eq. Dense Smokeless was about 11,000 psi.
12g 1 1/4 oz. 3 1/2 Dr. Eq. pressures were
well above the modern SAAMI 12g 2 3/4” maximum pressure of 11,500 psi.3. We have a pretty good idea as to the wall thicknesses the makers chose.
4. The makers had a “safety margin”. In the Birmingham Proof House Trial there were NO dimensional change in the 19th - 21st barrels, all Pattern Welded, until more than twice the Definitive Proof Load (DP about 11,000 psi) charge. In the Second Phase destructive trial, the 12th barrel (because of ties) Foreign Pointille’ Twist failed at 5.77 times DP and the 13th (last) Foreign Four Rod Crolle’ failed at 5.74 times DP.
5. My study, and one unpublished, showed NO evidence of the “because of low cycle fatigue, barrels get weaker over time” or “damascus barrels are a mass of rusting, delaminating welds” myths.
6. Fluid steel barrels DO have a bit less than twice the tensile strength of Pattern Welded and Decarbonized Steel barrels.
7. The safety margin for small bore doubles is less because the shell pressures are (in general) higher, and the wall thickness less for proper barrel weight. This may also apply the barrels of light weight 12b British game guns.
8. Bad things happen to barrels over 100 years through misuse; inappropriate loads (3” steel shells in 2 3/4” chambers), lack of cleaning, being dropped and dented, etc. and NO barrel, or any composition, can be assumed to be “safe” without a careful evaluation; which takes the time, interest, expertise, and tools to be done properly.
9. There is NO definitive NDT for pattern welded barrels, but we are getting much better at evaluating their integrity with bore scopes and wall thickness gauges.
