Chamber Dimension

[Austin W Hogan]

This is in response to some other current posts, but I am starting a new post to narrow the discussion. I was invited by the Fox Collector's and Julia Auctions, to examine the Super Fox to be auctioned Monday, and to prepare a Czar gun style article for the Fox Collectors Newsletter. My goal was to examine the legendary boring of these barrels. I prepared for this by rebuilding the jig I used for measuring choke profiles for Parker Pages about 10 years ago. This time I incorporate a "precision slide" that allowed me to measure barrel/choke/forcing cone/chamber diameter with respect to distance from breech or muzzle. The instructions for my Stan Baker bore gauge indicate it will measure a maximum diameter of .784 inches. I found that by seating the gauge in the barrel from the breech end, it would measure reliably to .788 - .792 if the movement of the gauge toward the larger diameter was controlled. Although the diameter measured was repeatable the distance from the breech to the point where maximum diameter was found was variable by about .060 inch due to the diameter of the measuring balls.
A photo of the measuring jig is shown. I measured 8 Parker barrel sets and 1 Fox barrel set at home to examine the resolution of this jig. A copy of my measurements is also shown. I measured the inside diameter with respect to distance from the breech end of the barrels at 1/8 intervals to a point four inches from the breech, and at 1/2 inch intervals to 6 inches from the breech.
The three Parkers at top have 32 inch barrels and trap gun like stock dimensions. 136683 (.790)has no safety and was made to measurements by DuBray, and included in the order "retarget before shipping. 170789(.787) is not in order books, but has a btfe, monte carlo no safety. 207489(.792) has a splinter, two triggers and an automatic safety.
The Fox is a C(.787) without ejectors with a BTFE and trap dimensions.
The three Parkers tabulated below the Fox are a 28 inch DH 216639(.775), a 30 inch VH 214194(.774), and a P hammer 159157(.775). The numbers in parentheses are the chamber diameter 2 3/4 inches from the breech.
The profile of the inside of the barrels of the gun ordered to Du Bray's measurement are shown in the sketch. My working sketch of the Super Fox is in green.
I have a plug type chamber gauge; it is .792 at the end. Note that all of these guns except 207489 measure less than .792 at 2 3/4 inches from the muzzle, including the 3 inch chambered Super Fox. The three Parker field guns measure .775; they are clearly 2 5/8 chambered guns. The sketches show that the plug type gauge is stopped where it engages the chamber taper NOT THE FORCING CONE.
The last time this subject was discussed on the forum, several of us made the joke that we had guns that were lengthened twice by the same gunsmith. This is the reason; a plug gauge can be stopped by chamber taper or forcing cone; but we can't tell which.

Best, Austin

[Dean Romig]

Thanks Austin. You always go beyond the norm in your analysis' of these old guns and how they were bored and choked and I find your findings fascinating. What conclusions may we draw about these guns you have examined and measured, especially the Super Fox in this case?

[Austin W Hogan]

Thanks Dean. I have the SAAMI manual here, and will post some of the figures when I have a chance. The current spec for 2 3/4 twelve gauge shells is 2.75 - .100 LOA, minimum 2 1/2 inches. I measured about 20 red and green fired cases and most are 2.66 LOA. That translates to 2 5/8 cases in 2 3/4 chambers.

Best, Austin

[Bruce Day]

Useful information Austin, and your 12ga fired shell length measurements are consistant with the shell length post I recently did. We get so many questions here " can I use 2 3/4" inch shells in my ........." The response is what 2 3/4" shells did you find to use?

[Terry Schraner]

I am trying to research the 20 ga. 3 in. cham. Parker guns, and shells available for them.What can you tell me about the history of the guns, and approximate availability. Thanks for a reply.Terry Schraner