Bore sizes

[Austin J Hawthorne Jr.]

Hey Guys, I'm looking for some input regarding Parker 10 gauge bore sizes. I tried wrapping layers of electrical tape around a 3/4 inch dowel one strip at a time....measuring the diameter.....and then inserting it into the breech end of an 1875 10 gauge lifter. If it slid all the way down the bore to the choke area, but did not exit the muzzle I figured it would give me the approx. choke for that barrel. Then I would add another layer of tape....measure it again... and slide it down the bore again. I repeated this until I had a snug fit midway down the barrel. This, I think, gave me an approx. bore size. What I found was a bore diameter or approx. .790 inches. I know that Parker overbored their early barrels but my question is was there a standard early 10 gauge bore size? Has anyone taken more precise 10 gauge measurements, and if so, what were the results? Thanks in advance for any info you would like to share.

[B. Dudley]

10g nominal bore diameter is .775"

Given the variation I have seen in Parker 12g bores, the amount that your 10g is oversized (using the electrical tape method) does not sound against the norm.

[Big Friend Ten (BFT)]

Early 10 bores were .790" approximately.

Mark

[10 bore]

I had a 1870's lifter 2 frame with .802 bores with .050 wall so i would say factory dia.??? my 1889 2 frame EH has .783 and my 3 frame 1890 EH has .780 dia bores. i would say you are very close to wright size on yours.

[Pa SxS]

One of you 10ga. guys should gather information and plot it on a graph like Austin did for the 12ga. The oversize bores on the 12ga. ran till approximately the 60k range, then went down to the nominal .729 range. That would be an interesting study.

[J. A. EARLY]

The 10 lifter on a 2 frame I just got is way over .792 (the highest my Skeets gauge will go where the gauge starts hitting the three inches of choke) and has barrels averaging .050 at the very thinnest spots. Where my gauge starts measuring to the end is .030 choke each so if I allow for the overbore I can't measure the overall constriction is pretty tight. 1878

[Austin J Hawthorne Jr.]

Thanks for all of the replies so far. Would anyone hazard a guess as to whether or not the bore diameter would/might be based upon frame size. My lifter is on a # 3 frame, and it has the step from chamber to bore ( no forcing cone ). Sometime today I will measure the chamber diameter with my High Tech Tape and Dowel, and will post it later

[10ga Hammer]

Posted this on another thread. 1878 10ga 2 frame. Can still see reamer marks in the barrels, has CC on 90% of breach face and roll joint. Gun was shot very little, both bores measure .792 with .23 choke. Many early 10's were overbore by todays standard.

[Pa SxS]

Robert, what does the rib inscription say for barrel steel? Your gun shows as PT (plain twist) in the stock book.

[10ga Hammer]

Yep, Plain Twist. Love the hand engraved rib.
Double click to enlarge.