Bore Diameters

Nightcrawler · March 20, 2001, 12:02 AM

Can anyone tell me the bore diameters of 20ga, 12ga, and 10ga? I'm just curious.

Also, how does the velocity of a 20 or 12 gauge slug compare to a typical big-bore rifle cartridge, say, .45-70, out of an equally lengthed barrel? I'm guessing the .45-70 is quite a bit faster, but I'm not sure how much.

Doc Hudson · March 20, 2001, 01:01 AM

Bore Diameter:
20 gauge = .615"

16 gauge = .662"

12 gauge = .729"

10 gauge = .775"

These measurements are approximate only since different degrees of choke will cause some slight variation, as will some variations between standards used by different makers.

As for the 12 gauge and 20 gauge slugs, the velocity is in the 1500 -1600 fps range. The .45-70's velocity can range from 1200-2400 fps depending on the bullet weight, powder charge, and rifle used.

Doc Hudson

Nightcrawler · March 20, 2001, 07:46 AM

So, basically, a good, hot loaded slug can give you the same velocity as a .45-70, with more mass and a bigger bore to boot. With a rifled barrel, you could probably be reasonably accurate out to 100 meters (this isn't coming from experience).

Hm. The shotgun IS pretty versatile.

Dave McC · March 20, 2001, 08:15 AM

The 45-70 has better sectional density and ballistic co-efficient,Nightcrawler. And...

For comparison's sake, both the slug guns here will print into 5 inches at 100 yards with the best slug, one runs closer to 4.That's edge to edge.

Last 45-70 I had would print into a 1 3/4" group,ETE, with dedicated handloads, 300 gr Hornaday projectile, X gr of 2400, Remington case and CCI primer. Weapon was an Italian RB, 28" bbl and vernier tang peep sight. Think, buffalo gun.

The accuracy laurels here go to the rifle. The ME is a bit larger with the shotgun,but the differences are more theoretical than practical on medium game.I'd be comfortable with either for same...

Doc Hudson · March 20, 2001, 09:53 AM

I agree with Dave. .45-70's, or any other decent rifle, are generally rar more accurate than slug guns and maintain their velocit better due to better designs for the bullets.

BTW, it is not hard to get a .45-70 slug that is heavier than most 12 gauge slugs, but it is also moving faster, has better velocity retention out to 150 yards or so, and usually penetrates better than most 12 gauge slugs.

I very much prefer rifles to shotguns for most hunting uses.

Doc Hudson

Monkeyleg · March 20, 2001, 05:51 PM

As long as we're on this topic: I forgot the origins of the use of "gauges" when it comes to shotguns, and it's driving me nuts. Isn't the gauge the number of lead balls of the particular bore diameter that it would take to equal one pound? i.e., twelve balls from a twelve gauge weigh one pound?

Deteriorating minds want to know.

Dick

PJR · March 20, 2001, 06:32 PM

Monkeyleg:

You got it. The gauge number equals the number of lead balls that add up to a pound. The exception is the .410 which is a bore measurement. The .410 is a 67 gauge or thereabouts if my deteroriating mind recalls correctly.

March 20, 2001, 12:02 AM	#1
Nightcrawler Senior Member Join Date: September 22, 2000 Location: Northern Michigan Posts: 2,945	Can anyone tell me the bore diameters of 20ga, 12ga, and 10ga? I'm just curious. Also, how does the velocity of a 20 or 12 gauge slug compare to a typical big-bore rifle cartridge, say, .45-70, out of an equally lengthed barrel? I'm guessing the .45-70 is quite a bit faster, but I'm not sure how much. __________________ Nightcrawler- TFL Alumnus

March 20, 2001, 07:46 AM	#3
Nightcrawler Senior Member Join Date: September 22, 2000 Location: Northern Michigan Posts: 2,945	Thanks! So, basically, a good, hot loaded slug can give you the same velocity as a .45-70, with more mass and a bigger bore to boot. With a rifled barrel, you could probably be reasonably accurate out to 100 meters (this isn't coming from experience). Hm. The shotgun IS pretty versatile.

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March 20, 2001, 01:01 AM	#2
Doc Hudson Senior Member Join Date: January 29, 2001 Location: Mississippi Delta Posts: 635	Bore Diameter: 20 gauge = .615" 16 gauge = .662" 12 gauge = .729" 10 gauge = .775" These measurements are approximate only since different degrees of choke will cause some slight variation, as will some variations between standards used by different makers. As for the 12 gauge and 20 gauge slugs, the velocity is in the 1500 -1600 fps range. The .45-70's velocity can range from 1200-2400 fps depending on the bullet weight, powder charge, and rifle used. Doc Hudson

March 20, 2001, 08:15 AM	#4
Dave McC Staff In Memoriam Join Date: October 13, 1999 Location: Columbia, Md, USA Posts: 8,811	The 45-70 has better sectional density and ballistic co-efficient,Nightcrawler. And... For comparison's sake, both the slug guns here will print into 5 inches at 100 yards with the best slug, one runs closer to 4.That's edge to edge. Last 45-70 I had would print into a 1 3/4" group,ETE, with dedicated handloads, 300 gr Hornaday projectile, X gr of 2400, Remington case and CCI primer. Weapon was an Italian RB, 28" bbl and vernier tang peep sight. Think, buffalo gun. The accuracy laurels here go to the rifle. The ME is a bit larger with the shotgun,but the differences are more theoretical than practical on medium game.I'd be comfortable with either for same...

March 20, 2001, 09:53 AM	#5
Doc Hudson Senior Member Join Date: January 29, 2001 Location: Mississippi Delta Posts: 635	I agree with Dave. .45-70's, or any other decent rifle, are generally rar more accurate than slug guns and maintain their velocit better due to better designs for the bullets. BTW, it is not hard to get a .45-70 slug that is heavier than most 12 gauge slugs, but it is also moving faster, has better velocity retention out to 150 yards or so, and usually penetrates better than most 12 gauge slugs. I very much prefer rifles to shotguns for most hunting uses. Doc Hudson

March 20, 2001, 05:51 PM	#6
Monkeyleg Senior Member Join Date: January 25, 2000 Posts: 4,625	As long as we're on this topic: I forgot the origins of the use of "gauges" when it comes to shotguns, and it's driving me nuts. Isn't the gauge the number of lead balls of the particular bore diameter that it would take to equal one pound? i.e., twelve balls from a twelve gauge weigh one pound? Deteriorating minds want to know. Dick

March 20, 2001, 06:32 PM	#7
PJR Senior Member Join Date: May 31, 2000 Posts: 1,127	Monkeyleg: You got it. The gauge number equals the number of lead balls that add up to a pound. The exception is the .410 which is a bore measurement. The .410 is a 67 gauge or thereabouts if my deteroriating mind recalls correctly.