Bore Gauge questions
 

Hi folks.. Just received my Gary Bulley 10-12-16 bore gauge. Damn what a great guy and product and price. Now for my stupidity to show, since this is new. I have 15-20 pieces to measure but want to be clear about something.

I have the 18" dial model and insert to get the bore reading, then pull out looking at the amount of constriction.

First question is, if "nominal" diameter is .662 (16g) and I get .665 or something, is that usually from boring out, or are Parkers pretty much consistent in their stated diameters? I have other guns to measure too.

Second, when measuring the choke, do I take the gauge ALL THE WAY until the little bearings are ready to come out? The reason I ask is that I'm surprised how much constriction one of my guns has. Going from .10 to .22! in like the last half to three quarters inch it seems. Barrels are factory length. I expected a much more gradual taper.

Finally, as I got this late last night and not much time, can I expect to go from the breech end and find forcing cones in a Parker?

Any advice, thoughts...etc appreciated!

The more open the factory bored thr chokes, the shorter the length of constriction.





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Congrats on the new toy! I have a Stan Baker all-gauge set and love it. As far as "nominal" goes, it is just that. I don't think a couple thousandths either side will make any difference and would be in tolerance levels.

In my experience measuring the choke area, I do try to get right to the edge of the muzzle, but make note of where the most constriction exists. I have seen some chokes (not Parker) that had a "huge" difference in the last <1" and some that have a long parallel segment, then a gradual taper and a few that actually close then open up at the end. So, I guess you can find any type choking but as far as Parker chokes, I can't say one way or the other what a 'standard' Parker choke looks like.

It is fun to see how consistent those "good barrels" are.

I appreciate the comments! It's a cool toy.

Austin Hogan plotted the bore and choke tapers on many Parkers and I have several of his graphs. I will post them here on the forum whan I can.
He told us that the Parker Bros. chokes began with an ogee from the bore into the taper and ended with an ogee from the taper to the parallel terminal 1/8” - 1/4” at the muzzle.





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Would love to see that Dean.

Great gauge but the price for the custom case was hard to swallow.

https://i.imgur.com/xfgrvlM.jpg
https://i.imgur.com/BNLzG6i.jpghttps://i.imgur.com/8wuDzmS.jpg?2

Yeah I got the gauge only. The custom cases are gorgeous, they're un used stock blanks. I'll probably just go to Harbor Freight and get a case and some foam.

Bore diameters vary with maker and era. I have a 1929 LC Smith 16 that measures .646 bores. .650 +- was standard for their pre 1930 era 16 ga guns according to those who know. .662 afterward. Similar thing applies to some Parkers. Early 12 bores typically mic'd .750+- according to research done by AH while later 12's came down to .729. Within those parameters, there is some small variation I have observed of 1-3 thousandths. Outside of that, I would suspect honing, reaming, or backboring depending on the amount. I would not worry about your .665 barrels. Whether factory or honed, its not enough to make a difference IMHO.

Thanks Mike, appreciate it.