doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Reproofed English 12 bore diameters

Just a quick question for the masses, would a nitro reproof Damascus barrel measured at 18.8 mm make you nervous about purchasing. .740 is quite the jump from .729 or 8.

Without knowing the wall thickness it is hard to say, .740" would be a loss of .0055" per side if the gun started out at .729". If the walls were .030" plus to start, then no worries. If it was struck up thin originally, and many were, then it may be of concern.

I would certainly want to know the actual current measured wall thickness before purchasing. But, for a bizarre illustration of dimensions, I had an 1879-ish Greener hammer gun that was proved at 12 and then presumably imported to the US near the time of manufacture. In the intervening 100 plus years the bores were enlarged to .783 i.e. 10 gauge with 10 gauge 2 7/8 chambers. However, the MWT in the distal third of the barrels was about .021 and it had approximately .110 at the forcing cone. Must have had a lot of wall thickness to begin with...

Also, what's it weigh? I would think something over or approaching 7 pounds with otherwise normal game gun dimensions might have slightly thicker barrels. Again, I would rather have the measurements or pay what it would be worth presuming the necessity of sleeving.

Agree with Dan. Current .740 is nothing to worry about—just an over bored 12. Heck, I have some totally original Parker’s with bores at or even greater than that. But wall thickness is everything. I see it still has original 2 1/2” chambers—that’s good. But what is wall thickness in front of forcing cone? And on down the bore? A lot of guns will pass proof with very thin barrels on down towards muzzle but be aware that they dent very easily and there’s not much metal remaining to repair.

.740-.729= .011. Had it been just .002 less it would not have needed reproofing. Any alteration greater than .010" requires reproof. Also recall that .011/2= .0055 wall removal. So if the walls were .035 to begin with they are now .0295. You do not know what they started out as so the need to measure is very much the only real way to know. Also that proof measurement is taken at 9" so at that point it has had .011 removed. You do not know if more has been removed elsewhere. Again measure the wall thickness for the barrels from end to end.

.740 wold not bother me in the least, if the walls are still .025" or greater. I would get more concerned if the walls are .020", concerned about possible future dents as much as anything. Again I want to know where the thinnest area is and decide then. At 20+" I would still shoot it with reasonable loads, but that is just me. And I have put a lot of worry into the math, the measurements and what "reasonable" loads are, which is as much a personal thing as anything. I shoot a 20 bore Pape that has a barrel with .017" wall, but that is 27" on a set of 30" barrels. Still I keep pressures down low and am careful about any actions which could dent it. It is a lovely hammer gun and a nasty dent might be the end of shooting her.

Have you weighed the barrels? My Webley 600 with 30" barrels weighs 1440 grammes (sorry about the Metric units...) whilst my Jeffery hammer gun, Farmer's Model, and shown as a 13 bore on the Proof marks weighs 1540, also 30 inches long.

HB

I don’t know the barrel weight, but the guns total weight with 30” barrels is 6.4.

If it's In Proof and the right cartridges are being used I would give it a second thought. As to overbored barrels I once had an English single barrel gun with Damascus barrels that started life as 16 bore and Proofed for Black Powder and later re-bored out and re-chambered to 12 bore and passed for nitro. Lagopus.....

to be safe, shoot 75 grains or less of 2f black powder and one ounce of lead shot, over fiber cushion wad...

when test firing, spread a bed sheet on the ground, in front of muzzles...if a lot of unburned powder is found on the sheet, reduce charge by five grains, until just a little amount of unburned powder is found on the sheet...that is your optimum load for this gun...

when pin hole leak appears in barrel wall, time to stop shooting and hang gun on wall...

Why would you shoot Black powder in a gun recently proofed for a nitro? That makes no sense at all. The Birmingham Proof house told me a gun I had which was reproofed for Black powder should be fine for 2 1/2” nitro loads. Sane loads would be fine. It seems there was not significantly more pressure in nitro proof in the 1930. Then gun is still well in proof. Guns can’t tell what powder you use only how high the pressure is. So keep the pressures down to 7,000psi, or if really conservative 5,500 psi and shoot the darn gun. There are a lot of sub 7,000 psi loads to pick from so why bother with Black?