Have seen a few previous post on here about trap guns having barrels that shoot at different heights on patterning ie 70/30 bottom barrel and 50/50 top barrel! just wondered if this is standard on all trap guns?
That isn't barrels shooting at different heights. That's the pattern placement percentage of the shot charge in relation to the point of aim.
A 70/30 comment means 70% of the shot pattern is above the POA and 30% below it. In comparison to the 50/50 mentioned the 70/30 would be a higher shooting gun.
All trap targets are rising in order to meet the height criteria specified in the rules. that's why most trap guns are designed to produce something like a 70/30 pattern.
My Miroku trap guns shoots both barrels in pretty much the same place as does my Perazzi MX8.
Daniele Perazzi had a theory that the first barrel was always shot at a rising target, but in some instances a second barrel was fired once the target had ceased rising and possibly a second barrel shot with a pattern placement the same as the first would miss over the top.
Whether his theory was put into practice by making the top barrel shoot lower I don't know.
I think that this becomes a classic case of doing a shooter's head in.
My only concern with a pattern plate is to confirm the pattern is going centrally, neither to the left or right. An 80/20, 70/30 or 60/40 pattern really doesn't worry me.