Caliber as bore gauge

[lanedh]

Who has, and can post, a table of conversion between balls-to-the-pound and diameter in thousandths (or hundredths)? One of my antique rifles has a number stamped on the face of the muzzle which should correspond to the old practice of stating caliber as 'gauge' numbers.

I think Ned Roberts' 'Muzzle Loading Caplock Rifle' had such a table but I can't seem to find my copy. Another brain f---t.

Thanks, guys

\\PS: the numbers are definitely not serial numbers, which appear in several places elsewhere on the gun and are different from the number on the muzzle face.

 

[Norskie]

You might outa try "Member Resources" I believe there is a chart converting caliber to grain wieght. If you know how many grains in a pound (I do not) then it's just math.
Moose

 

[Rebel]

Check in the members resources. I think there is a chart there.

 

[xxgrampa]

hi-ho moose-o,

it's 7000gr/lb.

..ttfn..grampa..

 

[paulvallandigham]

O jave a list copied off an old post here. Just tell us the number, and what you think your bore caliber is, and I can tell you if they are the same, or close.

 

[N6398]

Corrrect, 7000 grains to a pound and 437.5 grains to an ounce. The English system related gauges to the number of round balls of a particular diameter that could be obtained from one pound of lead. Hence, a 16 gauge (about .69 diameter or caliber bore) was a bore size that would yield 16 round balls of one ounce (437.5 gr) each. And a
20 gauge (.62 diam. or cal.) would yield 20 balls of 350 gr each--and so forth--you can do the math. You've probably seen references to even 4 gauges, i.e., 4 balls, each weighing 1/4 pound (1750 grains) from a pound of lead!

 

[renovato]

While the chart will come in handy, realistically, you should slug the bore to fit a ball to it. You never know the real bore size until you measure it. They did vary.

 

[almrl]

Hmm... Does the gauge refer to the diameter of the bore or to the weight of the ball and therefore diameter of the ball?

A .50 cal. shoots a .490 or 495 rb, a .54 shoots a .530, etc

I'm so confused.

Oh, 7734. Like Plink said, just slug the bore and get it over with.

Old Coot

 

[lanedh]

The Gordian Knot untied....(google Mythology).

Maybe I wasn't clear enough in my original post. I know about the chart in Member Services which gives the weight in grains of various sizes of pure lead balls. What I am looking for is a similar chart which has bore diameter expressed as gauge (so many balls to the pound as stated above)in one column, and in the opposite column is the approximate diameter in hundredths of an inch. That is, a bore size of 20 gauge would have an equivalent diameter of .62 inch.

This is more for out of idle curiosity than anything else; the rifle is a Nicanor Kendall underhammer with a bore so rusted out that if I upset a lead slug in there I'll have to drill it out. The bore is too far gone to use as is, and probably there's not enough metal left to bore out smooth and rerifle. It's consigned to being a wall hanger. Damn, but that would be fun to shoot, tho'....

Brgds to all,
Bluejacket

 

[paulvallandigham]

Gauging is a system of measuring the bore of the barrel by the number of round balls the diameter of that barrel's bore, that weigh one pound. A .50 cal. barrel is roughly 37 Gauge in size. ( Actually .501"). But if you are shooting a rifle in .50 caliber, you will probably shoot .490 balls, and those will be about 39 gauge( .492").

Here are the Gauges for common calibers of rifles.

.32 cal. ( .320) - 142 gauge.
.36 cal. ( .360) - 100 gauge.
.40 cal. ( .401) - 72 gauge.
.45 cal. ( .450) - 51 gauge.
.50 cal. ( .501) - 37 gauge.
.54 cal. ( .531) - 31 gauge.
.58 cal. ( .579) - 24 gauge.
.62 Cal. ( .615) - 20 gauge.
.66 cal. ( .662) - 16 gauge.
.69 cal. ( .693) - 14 gauge.
.72 cal. ( .729) - 12 gauge.
.75 cal. ( .751) - 11 gauge
.77 cal. ( .775) - 10 gauge.
.83 cal. ( .835) - 8 gauge( or Bore)
.92 cal. ( .919) - 6 gauge( or Bore)
1.0 cal. ( 1.052)- 4 gauge( or Bore)
1.3 cal. ( 1.355)- 2 gauge( or Bore)
1.7 cal. ( 1.669)- 1 Gauge( or Bore)

Now, as I noted above, about what the gun actually shoots being a round ball that is a few thousandths of an inch smaller than the bore diameter being a different gauge holds true for all the calibers listed above. I did not attempt, obviously to list all possible ball diameters you may use in a given caliber rifle, much less a smoothbore of that diameter! If you have a particular gun, and are shooting round ball, the easiest way to determine the " Gauge " is to weight your round ball, measure its diameter with a caliper or micrometer, so that you have a reference to THIS table, then divide 7000 grains( one pound) by the weight of your ball. The result will be the Gauge of that round ball, whatever size it might be. Don't be surprised to get numbers on the right side of the decimal point. If you check my table, the actual diameters of these " gauges " is close, but not exact for each " Caliber ". They are two different systems of measurement. They were not intended to relate to each other.

The system began when guns meant cannons, and cannons were made by casting the barrel around a mandrill or casting form to create the barrel. ( Think Mortars) Much of the early barrel making was done at foundaries that were already making church bells for hundreds of years, so that the similarity between a " bell " and a mortar, and later a cannon is obvious. When they got around to shooting small, single projectiles, that were not hand cut out of stone, they came up with the gauging system. Remember, that there was no agreed system of weights and measurements until the reign of Henry the Second. Gauging was a system created before we had millimeters, or inches, and fractions thereof. We use calibers, which are measured now in both inches, and millimeters, because they give a more precise measurement needed to create a barrel that can handle the kind of pressures we demand of it today.

MY thanks to Musketman for printing this table here on the forum back in February , 2006. ( Post #234540 )

 

[Norskie]

Have you considered having it lined? I know lining would be an expensive option if you just want to shoot it for fun, but it's the safest option.
Guess it just depends how loud the eagle screams on payday...
Moose

 

[lanedh]

Thanks Paul--exactly what I was looking for. The number stamped on the muzzle face of my rifle is "7(?)2"--somewhat obscured by rust and wear but pretty close I think. Actual bore size at the muzzle is considerably larger than what 72 bore/gauge equates to. This rifle saw a lot of use, and not very good care was taken to clean it (inside or out). Still in all, it's an attractive piece, with a really nicely figured rock maple stock.

Bluejacket

 

[paulvallandigham]

Be real careful when you measure bores on old rifles. Almost all old guns, made in the 19th century and before, have coned muzzles, so that if you measure the bore diameter at the muzzle you get the idea that it is very worn, when perhaps only the outer 1/4 inch has been worn oval through use. Cutting that barrel back a 1/4" or even more is not going to hurt the gun, but can restore its accuracy. have a gunsmith look at the barrel and tell you what you really have. I would hate to see you junk a perfectly good .40 cal. barrel, when all it needs is a little tender loving care.

My brother bought an old parts gun made in the 1870s or '80s, using a barrel that dates back to 1800. The stock was torn up, the hammer was missing, and someone had made a back action, left handed percussion gun out of it. He sent the barrel to Bobbie Hoyt, at Freischultz in PA. to have the breechplug removed, and the bore examined to determine its condition. Bobbie called him and told him he needed to open the bore up to at least 40 caliber because of severe pitting near the chamber. He called back a couple of days later, and told him that there was still a very deep pit that he needed to remove, but thought he could get buy opening the barrel to .42 caliber. He then re rifled the gun. However, the muzzle was not coned. Peter restored the stock, bought a replacement hammer from Dixie Gun Works, and got the gun back into firing condition. He found a .410 ball mold, and cast up some balls, and showed up at Friendship with it. We shot at practice targets off-hand at 25 yards. His first 5 shots scored a 48-2X. using 45 grains of FFFg powder. He later experimented and found it shot tighter groups with 50 grains of powder. He has been shooting that gun for the past 25 years, and more than one shooter has stopped by to look at that old gun, and learn about its history. I think what he did with that old gun did it far more honor than if he just hung it on the wall somewhere. He now has a .45 cal. rifle, with a De Haas barrel, that is super accurate, and is completeing another .40 cal. rifle, and underhammer. I told him the other day that I thought he should give some thought to having that old barrel lines and return it to its original .36 caliber, with a coned muzzle. He's thinking about it. He doesn't have a .36 right now. And like all of us, those .36 tend to seduce him.

 

[N6398]

Thanks for the chart; I have a similar one but couldn't locate it quickly. I also misspoke, equating a 20 gauge with .69 v. .62 cal.

 

[Claude Mathis]

Here's another chart.
[url] http://www.muzzleloadingforum.com/fusionbb/showtopic.php?tid/197045[/url]

 

[tg]

"A .50 cal. shoots a .490 or 495 rb, a .54 shoots a .530, etc'

untill probably toward the end of the ML era a gun with a .50 bore size would nave shot a ball of abot .47-.48 and would have been called a gun of about 42 balls to the lb. the caliber method we now use is a modern one compared to how the originals were refered to. Sometimes the gun was refered to as a gun of 42 caliber or 42 balls to the lb and would have the corresponding larger bore size.