A post on the Upland Journal site
http://www.uplandjournal.com/cgi-bin/ikonboard312a/ikonboard.cgi?act=ST;f=1;t=11527;hl=brian+meckler described a test of a 20 gauge M37. Forcing cone opened to 2-inches to start, choked 0.020-inches . Bore dia 0.615. Pattern tests with Remington loads from light field throught 3-inch Nitro Mags (#6 shot, if I recall). Tests were run as the barrel was opened 0.005-inches at a time with choke adjusted to remain 0.020 constriction.
Patterns at 0.615 were poor with all loads tested. At 0.620 patterns were better, but not good, even with the lighter loads. At 0.625 the ligher loads were much better, and the 3-inch loads were good. At 0.630 the patterns were excellent plus. Buffered 1-1/4oz Nitro Mags (6's and 4's) at over 80% - never want to trust my memory, so, the post is better for details.
Part of the explanation seemed to be that the wads were very hard to push through the 0.615 barrel. So hard, they were damaged by the effort. If narrowerer wads are available, the tighter bore may be able to do better.
The author of the post said he had difficulty getting 20 gauge to perform well. The test was done to see if bore size is a significant factor. Based in his results, I would say it is, at least, with modern wads. Used the M37 because the barrel is thick enough to take the overbore.
So, a 20 gauge can shoot very well, but the barrel at the start was very poor, and that is what many would use. We would not pattern test and see how bad it is.
Other than Invector Plus, Ruger RL and C. Geurini, I do not know what 20 gauge guns come overbored.
Last edited by J. Hall; 01/03/07 07:22 PM.
