Author Topic: Barrell wall dimensions (Read 719 times)

Buckshotliam · « **on:** February 06, 2003, 04:39:08 AM »

Howdy,
I've got a curiosity question. Why are BP rifle barrels so thick? We shoot heavy loads in our shotguns (ex. 100 gr FFg and 1 1/4 oz) and the wall thickness on my 12 ga is ~.025", and obviously strong enough. But the rifles are much more, my .50 rifle is 1.125 acoss the flats so wall thickness is .312". Is it tradition? Balance, to make the rifle "hang" out there in offhand shooting? Inquiring minds want to know.....

Buckshot Liam

River runner · « **Reply #1 on:** February 06, 2003, 05:44:47 PM »

I believe it has to do with making the rifle look period correct more than anything. The reason the original barrels were so thick, it was believed they needed that for the heavy charges of BP they were shooting. They didn't have the technology to determine the pressures; or the steels available to make them as strong as today. Also it was common to have their barrels freshed out, in other words a .54 bored out to .56 etc. This was probably due to the rust problem, as they didn't have the rust preventatives we have now. The shotgun being smooth bore was easier then as it is now to clean, so the tickness of the metal probably wasn't as crucial, however the few original muzzle loading shotguns I've seen had pretty thick barrels much more so than today. Maybe somebody else can add or detract from my theory. RR

P-J · « **Reply #2 on:** February 06, 2003, 08:19:52 PM »

I just measured my Navy Arms 12 gauge. Barrel wall thickness at the muzzle is about .050, at the breech it's three times that at .160 inch. The muzzle doesn't see much pressure so doesn't really matter. The major pressures of firing exist at the breech end.

That breech thickness isn't much smaller than minimum rifle dimensions. For example 13/16 is the smallest .45 caliber barrel offered these days, for a wall thickness of .180 inch.

Your .50 is 1 1/8 across the flats for styling, or maybe weight. .50s can be as small as 7/8, as I recall.

A curious aside: In Lyman's firing tests, shotgun pressures were less than half of rifle pressures. It's a big-bore effect, I think.

Buckshotliam · « **Reply #3 on:** February 07, 2003, 02:02:19 AM »

Hey,
Thanks, when you guys expain it it makes perfectly good sense!

Buckshot Liam

Naphtali · « **Reply #4 on:** February 07, 2003, 06:19:41 AM »

Original Plains Rifle barrels were made from "dead iron." Because metallurgy was primitive, and charges in these rifles were large/high, the sure way to insure safety and durability was increased metal mass.

By the time progress rendered the mass unneeded, the "look and feel" of a Plains Rifle was carved in stone.

Gerneral Julian Hatcher supervised destructive testing on M1903 Springfield barrels between the world wars. Barrels with chamber walls .125 inches thick withstood firing of standard military ammuniton indefinitely. Proof loads destroyed barrels, though, within three or four shots. See "Hatcher's Notebook" for more information.