I agree with Frank and Ed. I have yet to measure a 12ga Parker with fluid steel barrels that are .729, they seem to be in the .731 to .734 range. The majority of 12ga pre S/N 60000 are in the .740 to .760 range, these are top action guns.

Dean, I thought Becker back bored the guns he worked on. Did he over-bore them too?

TPS says that the Std size for 12 ga was .729. Maybe Parker didn't worry about being exact? Seems there are a lot of guns in the .734 range. I guess a few 1000's over made no difference to the machinist. It doesn't seem to me that .005 over would really make much difference. That size is hardly "over bored". Although in these modern times Beretta calls it's gun .005 over bored?

From what I understand, Becker lengthened forcing cones (reducing the angle) and over-bored barrels as well.

According to Michael McIntosh's A.H. Fox book "Becker's Super Fox forcing cones are 3/4-inch long and obliquely angled... Early on, Becker and Askins overbored their 12 gauge Super Fox barrels by .020-inch, from the standard .730 to .750... Eventually, in order to accommodate the widest possible range of ammunition, they established .740-inch as the standard Super Fox bore."

Cheers
Marcus

I believe that over boring to .740-.750 would make a difference. The modern guns that are backbored and overbored, ie Browning (backbored to .742) and Mossberg (overbored to .759), definitely pattern better in my opinion.

I can't see how .734 would make much difference so it may not have been done for any specific purpose.

Over bores
 

I have an under lever 2 frame with .765 bores that deliver beautiful patterns. It's great for long range shots when I do my part. Years ago I had a Stan Baker Perazzi single barrel with an .800 bore I shot trap with.
Cheers, Tom

That Perazzi barrel must have been paper-thin!

Perazzi Barrel
 

No, Stan Baker made the barrel himself, as he did many. I don't remember the wall thickness but it was standard thickness. I don't think the wad had a proper seal as the shot made a goofy sound. The pattern never was real good. Cheers, Tom

I kind of line up behind Researcher on this. It has been my observation that Damascus barrels in particular are oftentimes overbored, and not to anything that smacks of a common dimension. Having reamed out some light pitting myself, I am hesitant to think I am the first.