Here is some relevant info courtesy of Schuemann Barrels
. BTW, there is a lot of interesting information on that site if you look around some. Of particular note (to me), was the section on timing.
Ramped and Unramped barrels.
Both ramped and unramped AET barrels will be offered. A short history of ramped barrels is appropriate. When the 38 Super was first introduced into IPSC shooting, the barrels used were unramped which, combined with loading inexperience, caused cartridge case walls to occasionally fail because of the combination of high case pressure and insufficient case wall support. This led to Bar-Sto introducing a ramped barrel with Bar-Sto designed lower lugs. The Bar-Sto lower lugs were weak and failures led to the development of what we now call the Wilson/Nowlin lower lugs. This was a stronger design. About the same time Clark developed what appeared to be an even stronger lower lug design which ParaOrdnance incorporated into the ParaOrdance pistol design.
For a number of years barrels with the Wilson/Nowlin lower lug design outsold the Clark/ParaOrd lower lug design by two to one.
The Wilson/Nowlin design had less load carrying metal but a nice radius at the maximum stress point to reduce the stress concentration at that maximum stress point. The Clark/ParaOrd lower lugs had more load carrying metal but no radius at the critical maximum stress point to reduce the stress concentration there.
The actual strength of the two designed appeared equal because both the Wilson/Nowlin and the Clark/ParaOrd lower lug designs experienced a lower lug breakage rate of 1% to 2% per year, mostly because some gunsmiths haven't learn to properly time a 1911, and partly because the timing of a 1911 can change as it wears.
Lissner, a barrel maker in Australia, modified the Clark/ParaOrd design to include a radius at the critical maximum stress point. We introduced the Lissner modification into our Clark/ParaOrd ramped barrels in about 1997. Since that time there has not been a single Clark/ParaOrd/Lissner ramped barrel returned to us because of a broken lower lug while the slow steady stream of broken Wilson/Nowlin lugged barrels continues. I won't claim that the Clark/ParaOrd/Lissner ramp can never fail, but it is obviously stronger, and therefore inherently more forgiving of sloppy gunsmithing, than the Wilson/Nowlin ramp design.
It is easy to convert a Wilson/Nowlin ramped gun to use barrels with the Clark/ParaOrd/Lissner lower lugs. The conversion does not compromise the strength of the gun. Most gunsmiths eventually conclude that the Clark/ParaOrd/Lissner ramp is easier to install than the Wilson/Nowlin ramp. Our production, which used to be 2 to 1 in favor of Wilson/Nowlin lugged barrels three years ago has gradually changed to be 2 to 1 in favor of Clark/ParaOrd/Lissner lugged barrels today.
The growing popularity of the Clark/ParaOrd/Lissner lower lugs combined with the relative weakness of the Wilson/Nowlin lower lugs, combined with the fact that existing guns equipped with the Wilson/Nowlin ramp can be easily converted to the Clark/ParaOrd/Lissner ramp convinced us to offer the AET barrels only with Clark/ParaOrd/Lissner lower lugs, and in the unramped configuration where appropriate. The standard line of Schuemann barrels will continue to include Wilson/Nowlin lower lugs, Clark/ParaOrd/Lissner lower lugs, and unramped lower lugs, as it always has.
<font size=-1>[ This Message was edited by: Desert Dog on 2001-04-03 22:20 ]</font>