doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com So what gage is this?

No, I don't think too much progress was made as I switched the track at the juncture and all but derailed the hijacked train in pursuit of the gauge rabbit. 0.717" would calculate to 12.65 gauge which would put it well between 13 and 12 bore. I assume that the longarm is Damascus and dates in the 1866-1875 period. For "correct shooting" a "first class" set of tubes would begin as 13 bore and this was determined thru empirical data. Also, the Old English unit of an ounce(possibly direct definition-Roman influence while all of Europe but South of France and Italy considered 1/16 of pound as ounce) gave it as 1/12 of a pound and that coupled w/ empirical data could have lead to the choice of 12 bore. I would venture to guess that yours didn't require as much finishing as some. But I'm still puzzled how they made the made the lead spheres to get the plug gauges. So many advances(well about all) in gunnery occurred during the 19th century and as PeteM noted the barrel boring is very interesting.

Kind Regards,

Raimey
rse

Being of the machining trade, I'm puzzled as to why would anyone make a plug gauge out of lead. The first use would damage it. By the post Civil War era, machining had gotten pretty sophisticated. The Colt SAA and even some of the muzzle loading predecessors were machined nicely and have some difficult machine cuts in them. The history of measurement as it applies to inspection gauging is very interesting to me. Although I haven't found any particular evidence to support it, I think measurement methods were getting pretty sophisticated by the post Civil War era as well.

So as to not continue to derail this thread, I'll start another on the measurement subject.

It's a T. Newton of Manchester back action top lever hammer gun with nitro proofed steel barrels. I would guess from the 1890's.

With a bore of .685" the gun was a 14.47 gauge. The undetermined part is what shell was it chambered for.
Your bore of .717" is a 12.62 gauge but undoubtably was proofed as a 13.

2-piper:

What temp are you using for the density of lead? At room temp the density should be 707.937 lb/ft^3. I've taken a random sample of the gauges and calculated the diameter and if only varies a thousandth, if any, compared to the English proof charts.

Kind Regards,

Raimey
rse

Are You Sure it's a Shotgun & Not a Smoothbore Rifle? could be any # of Rifle Chamberings for a Smoothbore close range dangerous game rifle.

Raimey;
I took the 707.7 figure from a metals table in a Machinery's Handbook, temp was not given, assumed standard ref.
Interestingly though the same chart gave specific gravity as 11.342. Calculating out this gives a lbs/ft^3 of 708.
Burrard states ""In proof Acts & Rules the dia's of all bores have been calculated on the basis of a specific gravity of lead of 11.352. So if N is the number of the "Bore" or "Gauge", & d the dia of the bore in inches we get:
d^3 = 4.6578/N""
He then gives a chart showing bore dia's from 4 through 32, which are the same as found in the proof house charts. If his formula is followed for all those sizes several "Miss" by .001".
If however the formula;
d^3 = 4.65148/N
is used, all sizes from 1 through 50 + those 16 sizes from; 51.05 through 172.28 fall within ±0.0005 (round to three place dimension)to exactly match the proof charts. This however gives lead a specific gravity of 11.364. Admitttedly no sizes will "Miss" by more than .001", which is insignificant. Since however a figure (range) can be found where every size fits precisely, I can only conclude they did calculate with the same accuracy & number of significant decimal places.
I even considered "Perhaps" they did not round but "Dropped all digits beyond three decimal places. No luck, no number could be found that would bring all gauges no larger than chart sizes by .001" without having a few drop by .001" to a smaller dia. I can thus only conclude they calculated to the same precision I am using but used a figure for lead heavier than the SpGr of 11.352 Burrard stated, even though at the time of his writing he undoubtably obtained this figure from a proof house. Definitely heavier than the 11.342 most present sources seem to indicate.
The point is though, even though so slight as to be of no practical significance, there is a slight variation which indeed exists.
The Specific Gravities would give dia's of a 1 lb ball as follows;
11.342 = 1.6704"
11.352 = 1.6699"
11.364 = 1.6693"
Proof charts give the lb ball (1 gauge) as 1.669".

2-piper:

Interesting info and calucation. Most use the 11.342 at 293°K or 68°F or r.t.(room temp.). Thanks for the direction and I'm going to revisit Burrard on bore.

Kind Regards,

Raimey
rse

Maybe you should invest in this...

http://cgi.ebay.com/ws/eBayISAPI.dll?Vie...A:IT&ih=004