doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Drilling caliber marking

2 Piper, the difficulty in tying down specific gravity of lead and need to go to 8 decimal places are all indicative of why this gauging system fell out of use in favour of linear rather than a spherical/weight/element combination in the latter 1/2 0f the 19c. It is viable for shotguns but once you get into rifled calibers, especially the smaller ones made feasible by smokeless propellants it was found not to be effective.Regarding s.g. measurement metric is the preferred base measure although even this has changed from measuring at basic room temp (60-75f) to a more defined datum of 1 atmos @ 4c. The purity of available lead will also have changed since gunmakers adopted this system.

Typical of drillings from the period, the following sequence of marks, beginning just under the forend lug on the rifled tube, will be found representing the proof events:

Imperial Eagle Crown over G
Imperial Eagle
Crown over U
plug gauge diameter(sometimes horizontal, sometimes vertical)

I haven't seen a pic yet but from what Jani describes the much maligned "248" holds the position of the diameter of the tube. If those are the only marks, by process of elimination the "248" would somehow relate to the tube diameter.

If not "248", where is the mark for the diameter of the tube?

As far as the value for lead, assuming pi to approach infinity, and using the published data from the British Gun Barrel Act of 1868, the value for lead can be calculated.

Kind Regards,

Raimey
rse

The Casio calculator I use is a 10 digit model so when I punch in Pi I am working to 9 decimal places. The figure I use which relates to the lead density of 11.365 grams per cubic centimeter corresponds with the cited '68 Gunbarrel Act chart in all 50 gauges 1-50 plus the additional 16 from 51.05 (.450")- 172.28 (.300") in .010" increments to the nearest .001". This is heavier than I have ever seen the density of lead given & would think it unlikely they had any adultrated with a "heavier" constituent. This is however heavier than I have ever seen given for the density of lead. Two possibilities come to mind
#1 They simply mis-measured the volume of their "Standard".
#2 It was suggested by another member, but don't recall now to give credit, that perhaps they used some method of bring the Standard to roundness which resulted in a slight compression of the lead leading to a smaller dia. This sounded very plausible to me.
At any rate & especially considering all their calculations involving cube roots etc had to be carried out by hand, their math was Simply Stellar.

Raimey wrote:
"If not "248", where is the mark of the diameter of the tube?"

This is my thinking also.

In the meantime I made a wax positive of the chamber and measured it. Not surprisingly it matches the 7x57R just fine.

Jani

Reading thru this thread I'm not clear that the 2XX mark is indicitive of bore diameter. My view/opinion is that the proof house had a cartridge number requirement for any particular drilling/DR that may have passed thru their doors. (This mark/number designator would of course be somewhat time period dependent) In other words the 2xx number might correspond to 7mm Rimmed (7x57R) Also and it needs to be noted here that the "181" mark on drillings and and ocassionally seen on DR tubes equates to .30-.30 Winchester not 303 British. (This from German guns that I have owned, handled and inspected) I currently own a Sauer Drilling with "181" on the barrel and it is most definitly chambered for .30-.30 In regards to the three digit caliber marks, thus far I have only seen the '181' mark but have been looking for others....so the 2xx mark is intriging to me. Does any one else have any marks similar to above stamped on barrel(s) for known calibers/cartridges? I am not discounting Ellenbr and 2Pipers work and thoughts on the barrel marks but until I see more evidence that it all pencils out (bore/gage), for a number of other cartridges/calibers I remain....curious. Jeff

Well, I'm pleased to see that a few read the drivel I post and call my hand at it. First, the plug gauge mark wasn't for a specific calibre and was just for a diameter which the plug passed the whole length of the unrifled tube. As I posted before, any calibre not listed in the law/articles/proofhouse data sets had to be submitted in writing to the proofhouse to determine the 1st and 2nd proof loads. Also as I've posted before I have a Buchel Stechespanner by Srba in 8.15X46R that has the "181" mark and I have seen at least 1 other target arm with that stamp. Mr. Cate gives double rifle serial #131857 as a 0.303 British and having the "181" stamp. So with Jeff's 0.30-30 double rifles and drillings, it futher supports the case that the proofhouse did use plug gauges less than the published 172,28 mark. Although for all non-standardized/early calibres there will be a range of diameters, 184,11 is the one that I've seen associated with 0.30-30(7.62X51(53?)R/30-30 WCF/30 Winchester). I've seen info suggesting a linking 184,11 with 32/20(32 Winchester/8.1X33R) and 32/40, but I've also seen 156,14 coupled with 32-40 Win. Then there are other bolt rifles and Kipplaufs in 25-35(6.5X52), 25-20SS(6.5X41R), .22"(5.6X15R), etc. which would have had a plug gauge stamp for their diameters also. I guess it would be best to convert everything to metric and get a range of plug gauges for each calibre. As always, there were exceptions to the rule.

Kind Regards,

Raimey
rse

Raimey;
I for one have throughly enjoyed this exchange & feel I have learned a lot from it. I had wondered on occasion just how bores smaller than 172.28 (.300"/7.62mm) were marked during this era but had not had opportunity of examining one.
Interestingly doing the conversions on these reveal;
181 = .2951"/7.5mm)
184,11 = .2934"/7.45mm)
To have followed the system adopted from the British with the larger sizes & dropped an even .010" to .290" (7.37mm) would have given a plug of 190,72 gauge.

Me, too - very educational and enjoyable. I'd gauge it a complete success!

Jani, 248 means Gauge and stands for 6,8 mm plug.

Geno:

Do you have addition "small bore" listings for gauges smaller than 172,28?

It's close and probably just semantics but I think it was for 6,75mm and 2-piper may have run upon something in that they were using 0,05 mm increments on the subgauge around the chambering, but this is just pure conjecture on my part. Also, I think PI to have been considered 3.14 and the mass of lead was some integer or 1/2 integer value like 708.5, 709, 709.5(lb/ft^3), that is if they used English units. I'm beginning to think the calculations were all in metric and they performed some type of mm to inch conversion. Really without a chart, or a lot of examples, all we can do is perform calculations using diameters that approach the prescriptive plug gauge value.

Kind Regards,

Raimey
rse