Parker 12ga bore diam.

[Bruce Hering]

Just checking my bore sizes. I have a GHE 12ga (1925) with Parker Special Steel barrels that shows bore sizes R .737, L .736. Do these sound-like original bores or have they been "honed".

Thanks

[Randy G Roberts]

Bruce I believe that TPS will tell us .729 is the magical number. However I do not have any 12 gauge guns that actually measure that. The smallest bore that I can find in my group measures .731 in each bore. In looking at a half dozen or so others they all seem to range in the .733 to .736 range. Based upon my selection I would have no issues with the measurements you cited. Some of the guns I cited above are minty and undoubtedly never messed with so I feel comfortable using them as a guide.

[Bruce Hering]

Bruce I believe that TPS will tell us .729 is the magical number. However I do not have any 12 gauge guns that actually measure that. The smallest bore that I can find in my group measures .731 in each bore. In looking at a half dozen or so others they all seem to range in the .733 to .736 range. Based upon my selection I would have no issues with the measurements you cited. Some of the guns I cited above are minty and undoubtedly never messed with so I feel comfortable using them as a guide.

Thanks Randy.

[Garry L Gordon]

Bruce, I most certainly agree with Randy. It is seldom that my gauge measures exactly .729. I don't know just when Parker stopped overboring, but my older guns -- hammer guns and hammerless -- as I recall have larger than current nominal bores. Some may have been honed somewhere down the road, but I still think older guns are likely to have bores larger than .729.

Do you know the wall thickness at various points of the barrels? I like to know those more than the diameter. If you were closer...

[Bill Murphy]

Duplicate post

[Bill Murphy]

More likely than "been honed" would be "your micrometer isn't quite accurate" or "you didn't quite measure correctly". No big deal, that's just the way it is. What brand of micrometer are you using, or is it a micrometer at all? I'm guessing your bores are just fine.

[Andrew Sacco]

If someone was to shop for a tool to measure this on the used market, what is the best tool?

[Kevin McCormack]

If someone was to shop for a tool to measure this on the used market, what is the best tool?

For my money, Hosford's gauges hands down. They are expensive but they are incredibly accurate. His bore/choke gauge uses tiny collapsible fingers (3). I have run some comparison tests against a c. 1970s ball gauge which uses 3 small spheres on the brass head, which has proven to be very accurate. The range between the ball gauge and the Hosford gauge has never varied more than .003-.005 for the some 50 guns I have measured with them. No mystery using his instruments (he also makes an incredibly accurate barrel wall thickness (BWT) gauge.

[Mike Poindexter]

Austin H. put out an analysis of 12 ga. bore diameters on this forum years ago. He found that prior to S/n 70,000, there was a distinct "node" or cluster of guns bored .750-.755 , with a lesser node in the .730-.735 range. After 70,000, the large diameter node disappeared. I am attaching what I copied from his post back then.

[Bruce Hering]

More likely than "been honed" would be "your micrometer isn't quite accurate" or "you didn't quite measure correctly". No big deal, that's just the way it is. What brand of micrometer are you using, or is it a micrometer at all? I'm guessing your bores are just fine.

Bill: Yes, its a bore mic, Skeets. It seems pretty reliable checking against bore sizes measured with one of the "fancy" ones.

[Bill Murphy]

I also use a "skeets" type micrometer that I bought from Galazan years ago. I also have a great instrument sold by Galazan that measures 10 to 28 and sells for more than $400. I don't know if this one is still in Tony's catalog or not. It works without any springs and is very accurate.

[Daryl Corona]

I've got the Galazan gauge and find it is accurate enough but it won't fit into the muzzles of my 28 Parkers or my Pieper 28. Those I use the Bore Master which once you learn to use it is accurate enough.

[Garry L Gordon]

I checked my record log which has bore diameter listed. My gauge is the one sold by Brownell's. I'm listing the date of manufacture for that reference.

.754/.754 1884
.753/.753 1886
.751/.756 1889
.761/.762 1889
.752/.751 1890
.753/.753 1891
.753/,753 1893
.734/.736 1896
.735/.734 1904
.732/.732 1912
.733/.731 1923

A small sample size, but it is suggestive. All of these guns measure with sufficient wall thickness (in my estimation and based on advice gotten from members here), and all have been shot numerous times.

[Arthur Shaffer]

I don't know how to reference a thread number, but I started a thread on 12/8/21 titled "11 gauge" on this very subject. You can go to my profile and read the 2 pages of comments. I brought up this issue of 10 vs 9 gauge and 12 vs 11 gauge. I found reference in the Parker Story that the writers believed that the standard 12 gauge had 11 bore barrels and the standard 10 gauge had 9 bore barrels. Their writeup stated that with paper shells coming into play, there was a mixed market and it was mot until March 1892 that the stock book contained a note that henceforth, unless the barrel was stamped with an "O" that it would be a normal 12 gauge barrel. I presumed that the "O" was meant to indicate oversized or overbored. They further stated the same notice concerning 10 gauge was included in the stock book "a few months later".

Chuck joined in and said he had never seen these notes in the stock books and asked for a detailed reference, I went back to TPS and posted the actual page numbers in TPS and the date called out in the order book. I was (and still am) hoping that he can either confirm these notes or disprove the accuracy of the discussion. To date I am not aware that this has been done. Since no one else has access to the records, the research people will have to do this.

This would settle a couple of the long standing issues collectors have, including the honed/not honed and 12/11/10/9 gauge discussions that go on, and the other is the meaning of at least a lot of the mythical "O" stamp questions.

My main concern then was that most people don't own bore gauges, and when someone finally had access to one, they immediately decided that they own a very rare and desireable gun. A lot of collectors, even some acknowldged experts, seem to take the position that if the barrel is 11 gauge, it is an 11 gauge gun. This was/has not been true in other countries with proof laws and was not wholely true with Parker until around 1900. There are scholarly articles in Double Gun Journal that take this position. I personally think that the term used should be chambering instead of the improperly used gauge when refering to a shotgun. You commonly see an English proofed gun that has 13 gauge barrels with 12 gauge chambers, and are marked as such. Unfortunately, the Serialization Book lists the column heading as B for bore but I suspect that more often the data there is the chambering.

Read the entire original thread to see more comments on this question.