Parker Bore Diameters
This topic arises several times a year. I think the attached table was posted on the old forum, but I have annotated it with pertinent numbers. The table is based on measurement of bores and chokes of 58 Parker guns with s/n from 284 to 241000 plus. This was prepared after many discussions with Charlie Price and others; Charlie indicated in TPS that Parker boring changed at around s/n 70,000 in 1892. This frequency analysis verifies this; Parker choke boring changed again with the move to Ilion. This was covered in PP articles on the closing of "The Parker operation".
The barrels measurements in the table are from 12 gauge guns. Each was tested for 12ga chambering from being listed as such in "Serialization.." ; by chamber diameter of .810 +/- .005, or both in some instances. The bores were measured at several places with a Stan Baker gauge. The individual bore diameters at mid barrel (15 inches from breech and /or muzzle) are listed in .005 inch classes in the table. A pattern began to emerge as the data was tabulated; there are definite modes of the numbers of barrels found with respect to bore diameter. A mode is a (bore) size class where more items are found than in adjacent size classes.
There are no modes in the diameters of barrels bored prior to s/n 5000. Damascus and laminated barrels are not homogeneous and are very difficult to machine with uniformity; King's mastery of tooling minimized these difficulties. Prior to King's innovation, barrel boring was cut and try, and reaming and polishing continued until the barrels were smooth.
There are two distinct modes of diameter in barrels 5000 to 70000; one in the .735 - .740 inch class, and a dominant mode in the .750 - .755 inch class.
There is a single dominant mode in the .730 - .735 inch class in the barrels made following serial 70000. "Emery out barrels" is a frequent note in early Parker order books, as Dave indicates. Were barrels of larger that .730 diameter the result of cleaning out, we should expect to find many barrels, in the .740 - .750 diameter classes; that is .010 - .020 polished away. The measurements show a minimum mode here in both eras.
There are two conclusions one can draw from this tabulation; Parker made few 12 gauge guns prior to s/n 70000. The shooters loaded 11 ga loads in available 12 ca cases.
OR
Parker's tooling was based on American industry of the time which worked in increments of 1/64 inch. Barrel blanks were pilot drilled to 11/16 (44/64) (.6875) inch ID followed by a rough boring of 23/32 (.718) inch, leaving 6 inches behind the muzzle .6875 to accomodate finish choke boring. This was followed by a 47/64 inch reamer. Some barrels cleaned up with this first reaming and polished to the .735 - .740 range, acounting for this mode. Those that did not clean up were reamed 3/4 inch and polished out to make the .750 - .755 mode. The convincer about this is Parker's nut borer which scraped metal away in an ogee curve to allow barrels to be choked to deliver, independent of bore or choke diameter.
It is evident that Parker's boring changed after s/n 70000, as a clear and distinct mode at .730 -.735 appears, and the .750 mode is absent. This may have been a result of the revolution in steel making at that time; or to production of ten times as many shotgun barrels with the appearance of the W93/W97 that made specialized barrel tooling readily available.
I have absolutely no idea of the speeds, feeds, and cutter designs used to machine damascus. I have discussed this with master tooling engineers Dave Suponski and Larry Frey. I hope that enough material will be found to support some comprehensive coverage in Parker Pages.
Best, Austin
Last edited by Austin W Hogan; 10-01-2009 at 09:54 AM..
Reason: Grammar and Punctuation
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