Deciphering barrel thickness

[Rick Riddell]

Had a set of barrels checked, but not sure what I’m looking at? Any help would be great!

[OH Osthaus]

I cannot read all the comments- "overboring" might be factory on an early gun

i am surprised the serial number an steel type is not mentioned
,
over all, a through set of data points,

good meat in the critical back end - 33 as a minimum 9 inches from the muzzle would please most folks,

if these are unpitted barrels - it all looks good to me

[Rick Riddell]

Oops I thought that was on there, GH Damascus barrels, no pits , it was a family gun ( not mine) from 1903, sent back to Parker in 1913 for work, I had it opened (my bad) but there was no other family work history on it.

[Mike Poindexter]

The only point confusing to me is the item listed as "Minimum Thickness" under the Left barrel, where it says 0.142" @ End of Forcing Cone". Based on the data points above it, it appears that he measured the thickness at the end of the forcing cone on the Left barrel to be 0.103." It appears that he lists the recommended minimums for each location on the left column, much like your bloodwork report at the physician's office shows the recommended values for different enzymes, etc. in your blood. Your gun's values appear to fall within his recommended limits, except possibly for the Right barrel at the end of the forcing cone, which shows a value of 0.076", which is less than the recommended 0.100." You might give him a call for a better explanation, and his opinion whether the barrels appear safe to shoot with lower pressure loads. Best.

Mike

[Dean Romig]

I would be more interested in the wall thickness at the BEGINNING of the forcing cones.





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[Rick Riddell]

So the confusion was with the form I got online, I spoke with Mr. Fey, the .170 -.076 is the span of the forcing cone which is about 10 inches, so .170 at the start and .076 at the end. the left was 7 inches respectively. So somewhere between the original owner, the work that Parker did and the gentleman who inherited the gun, the right cone was lengthen. If I keep it at low pressure loads it should be fine, if that makes sense

[edgarspencer]

Originally Posted by Rick Riddell

So somewhere between the original owner, the work that Parker did and the gentleman who inherited the gun, the right cone was lengthen. If I keep it at low pressure loads it should be fine, if that makes sense

Another possibility is that the right barrel had some honing done to remove pitting in front of the forcing cone.
Don't quite understand the figure for the left barrel "Minimum wall Thickness"

[Drew Hause]

The barrels have been honed and possibly the chamber lengthened from 2 5/8" to 2 3/4".
At least an estimate of the length of the forcing cone would be very helpful.
The "end of the chamber" is clearly the breech end, not the forward end immediately before the forcing cone; and that is the critical number.
I can only assume that the thickest part of the F.C. is .169" and .170" and the toward the muzzle end of the right (I'll bet lengthened) F.C. is .076". If that number is actually the end of the chamber the barrel should not be used, with any load.

This helps show that the WT of the F.C. is usually greater than the end of the chamber because the angle of the cone is greater than the external taper of the barrel



I would confirm
1. What was the WT at the (forward) end of the chamber? (which BTW is that .105" recommended number)
2. What is the estimated length of the F.C.? (After looking down the bore of lots of barrels it's not that hard to tell the turn-of-the-century 1/2" - 5/8" cone and a lengthened cone.)

The CIP recommendation for "standard steel" (something like 4140) at 4" is .075", but pattern welded tensile strength is a little more than 1/2 of 4140 so .076" would certainly be considered low, and 4" is pretty close to some important body parts. I would most certainly only use low pressure loads in the right barrel.

[Rick Riddell]

2 3/4 for the chamber, the bottom narrative on the paper got cut off, yes .170 (chamber)at the start and .076 (muzzle)at the end, 10 inches in length for the right barrel. Those other numbers at the description are from the form on your site. The left minimum thickness at the bottom should be .103@end of the 7 inch forcing cone. Wow we really are deciphering this!

[Drew Hause]

OK. Was thinking and typing before the length of the F.C. clarification. .076" at 10" is certainly adequate.
And I agree with Edgar that these looooooong cones are the result of honing; pitting is usually worse into and just past the cones.

Looking toward the breech from just past the cones (barrel has been cut)



Again - please confirm the forward end-of-the-chamber WT, and please let Mr. Fey know that the "end-of-the-chamber" recommendation of .105" is the forward end; not the breech end.
And BTW: .200-.210" is typical breech WT for U.S. 12g chambers