Hi Guys. Well I tried a variety of .355 and .356 heads but still the same sort of grouping. A bit better but nothing startling. I did think I was onto something when my first 4 shots made one ragged hole but then had two fliers about 2 inches away in two different directions.
An interesting development though, I got in contact with Krieger Barrels - oh to get one of those - who gave me that according to the SAAMI the .357 should have a bore of .346 and grooves to .355. The question is that is this just for rifle barrels (mine is a Bergara rifle barrel) and should revolver .357 barrels be just that - .357 when shooting lead?
Krieger have offered to do me a barrel at .346 bore/.357 groove. Would that be too much groove and start shaving lead.
I note all your earlier comments. Although the forcing cone is 11 degree, should it be longer than the .075 it is now. The crown is also 11 degree cut straight to the rifling. Should I have a shallow flat recess around the exit hole or what?