.729 the magic number

Rick Riddell · 06-22-2018, 07:12 AM

Now I know not all Parkers measure this number, is there a time frame when barrels would deviate from this standard? What range of numbers would you consider acceptable for Parker variation in bore diameters? Would there be any indicators that would suggest the barrels had been honed if the diameters were larger than the standard?
Thanks guys!

B. Dudley · 06-22-2018, 07:43 AM

It went up and down over the years. The late 1880s had some of the larger bore diameters that i have seen. As high as .755+.

I woild say that things did not settle down into what we consider normal siameters today until the 1920s.

Wall thickness and the overall appearance of the bores are indications of any issues.

Rick Riddell · 06-22-2018, 08:14 AM

Brian, thank you. Would it be uncommon to see a gun from the early 1900's with different bore diameters in the same set of barrels? I have a set that measure .736 and .740. Thickness averaging out to:
RB .041 and LB .054.
I had them inspected and they were safe to shoot. I just want to learn more about the whole process.

B. Dudley · 06-22-2018, 09:58 AM

Usually the bore diameters from tube to tube will be close. But a few thousanths is not out of the ordinary.

Harry Collins · 06-22-2018, 11:45 AM

Away from my notes, but this is what I remember:
VH two barrel set .728 .015
.729 .025

.734 .030
.733 .042

Trojan .734 .030 .737 .040
1881 Lifter .751 .013 .752 .013

Kevin McCormack · 06-24-2018, 05:44 PM

I once miked a 1911 CHE pigeon gun that measured .750 in both bores at midpoint.

J. A. EARLY · 06-24-2018, 10:12 PM

I picked up a basket case 12 gauge Crescent Arms gun and had my brass gauge with me. It told me there was still choke left in the gun, being modified and modified. The barrels were stamped "Choke Bored."

When I got home I measured the bores and both were .710 all the way to the end, cylinder and cylinder in cut barrels. I am wondering what advantage did they gain by deviating from the standard .729 and the gun is hammerless so it had to be made when there was some standardization in the 12 gauge bores.

I wish I could have know how much choke was put into the gun to achieve a hardware store gun with probably full chokes.

Harry Collins · 06-25-2018, 08:29 AM

Many European guns have bores in the vicinity of .720