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July 12, 2007

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The Truth About Overbore Capacity

In my formative years, I read a lot in P.O. Ackley’s books on wildcat cartridges, and as a result, I worried a lot about overbore capacity and barrel life instead of the war in Vietnam, nuclear conflict, and the price of gas, which had hit 75 cents a gallon. Overbore capacity, for those of you who are not familiar with the term, refers to a cartridge case that burns far more powder than it can efficiently use in exchange for a proportionately small increase in velocity.

This past weekend, I worked up a handload for my Ultra Light Arms .340 Weatherby, a rifle I’ve owned since 1993. The .340 is actually .338 bore diameter, but where a .338 Winchester takes about 70 grains of powder to give a 250-grain bullet 2,600 fps, my Weatherby uses 88 grains to push the same slug at 2,775.

Holy Barrel Burnout! Eighty-eight grains of powder is a load, and I thought there was no doubt that my lands and grooves were scorched to a cinder. So, filled with an overmastering sense of doom, I put the bore scope in the barrel and lo and behold, the rifling was as shiny and sharp as the day it left the Douglas factory.

The truth is that very few people shoot big magnum rifles unless they’re either crazy or have way too much money. Even with 14 years on it, that rifle has simply not had much use, and its barrel will last much longer than I will. Is the extra velocity worth it? Yes, marginally. Up to 300 yards it doesn’t make much difference, but beyond that, it can.

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Comments

Steve imposter #53

Well if you can't increase B.C. it's all you got

Thos. B. Fowler

I remember the dire warnings about overbore capacity, too...and have to admire something like the little .222---so efficient, and does a number of chores well, quietly, inexpensively. But, like Robbie Frost observed, something there is that doesn't like a fence--and sensible cartridges seem doomed for the bigger bang.
Recently, I had to load up some standard 8mm rounds for a backup rifle for an elk hunt...and this round, which I had sort of lumped in with the '06 as an overbore round, turned out to be just right when loaded with H380 and a 180 gr. Barnes boat tail. It was even a mildly compressed load, which brought back memories of Dad loading his old 7mm with surplus powder that way. 'It cannot be overbore...hear it crunch?'

I suppose that as long as we have the marvelous American mind at work, we will have campfire arguments over the 'fences' of calibers and perfect loadings. It is in the nature of America.

Tom Fowler

Steve C

I agree that bore or throat erosion are overrated for modern firearms.

Short of, say, a varmit hunter that shoots the same weapon for 30-40 years, you'll never put enough shells through a regularly maintained gun to make a difference.

That said, magnums are generally answers in search of a question. Particularly true of the uber-magnums.

Jim

According to the theorists, the little .30 M1 Carbine round is about as efficient as you can get. However, the 30. Carbine round makes a lousy big-game cartridge. One thing we must not do is confuse efficiency with effectiveness. A .340 Weatherby may not be that efficient, but it surely is effective against anything that walks the earth. There's no doubt as to which kind of firearm I'd rather be carrying when the game is tough or the ranges are long, or both!

Yongary

"I agree that bore or throat erosion are overrated for modern firearms."
I agree, many sportsmens' rifles rarely see 20 bullets a year, especially using expensive ammo, but some people fire over 3000/year easily, so it is still a concern in some rifles

Ralph the Rifleman

Dave-
Is that .340 for sale?

WA Mtnhunter

I read an article about cartridge efficiency in one of the gun rags a couple of years ago. It was done by one of the more credible writers, although I can remember who. Anyway, it addressed cartridge efficiency as energy and lethality factors versus the amount of powder burned. I was surprised that the .257 Roberts Ackley Improved and the .35 Whelen Improved were at the top of the heap. The .308 Win was right there too, as I recall.

Eric

I shoot my 330 Wby a lot and I shoot it fast, just like you would if a follow up shot is necessary and it just keeps shooting TIGHT groups with about any load I put in it. Same for the 257 WBY and the 270 WIN. Whatever throat burn does take place will never make a differnce in a hunting rifle. Burn away!!

Joey

Are handguns up to burn out or is it just rifles that use the bigger power charges?

Jimmy

Overbore capacity is only a state of mind for any regular person. Magnums and high velocity are the only barrel burning factor and aren't prevalent until you shoot thousands of rounds. Besides, if you can create higher bc's by even a little bit, you should load that baby hotter.

WA Mtnhunter

The 30 carbine is efficient for light game and people, especially in a defensive situation. What dumba** would think about using it for big game anyway loser?

R Dorn

I spent the better part of this afternoon trying to locate the "gunsmithlocator.com" web link at Midway without success. I also did several searches without luck. Is it a phantom of someone's imagination or what? I've been trying to locate a gunsmith named Roderiquez for several years...ever since seeing a picture of Craig Boddington's "Roderiquez 7x57 custom mauser" Can anybody direct?

Jim

I'm being on the way past 50 side of things, I've saw and have barrels shoot out even in the .222 & .243. I have a Remington .243 on it's 3rd barrel, but to me when group size gets much past .75" I have no use for the barrel.

My Dad shot a S & W .357 so much the backstrap was not repairable per S & W. He had gotten his wear out of it and simple bought another. I have his third one and still shoot it today some.

I personally think most folks don't shot enought to be good shots, much less wear out a barrel. It's just not that easy any more to step out the back door and shoot as I did as a kid. We would burn way over 2,000 rounds each on a good weekend at P. Dogs and never even get off our own farms. We had a 600 yard range about 100 yards from the house and I hunted every day of Nebraska's Pheasant season. Today I'm luck to get in 10 days of Pheasant hunting. P. Dogs are limited to 6 or 8 trips a year and less than 20,000 rounds.

Now I spend a great deal of time training folks how to shot CVA Muzzleloaders and my many rifles will get way over 25,000 rounds sent down there barrels each year. Tomorrow is a FREE GAMO Air Rifle Shoot at the Kansas City, Kansas Cabela's where I'll be taking 15,000 pellets and plan to come home without any. I hope every kid and every kid at heart gets to shoot until they are tired! I provide everything from the guns, pellets, balloons, animal crackers and all kinds of fun targets. I'm just trying to pass the shooting sports on to every kid I meet. Same for fishing.

I personally think most folks don't shot enought to be good shots, much less wear out a barrel.

agree

It's just not that easy any more to step out the back door and shoot as I did as a kid. We would burn way over 2,000 rounds each on a good weekend

2k? NFA??? wtf?

Clay Cooper

338 Winchester takes about 70 grains of powder to give a 250-grain bullet 2,600 fps.

What powder you using!

70 grains of IMR4350, Federal 215 primer and a Nosler 250 grain partition runs across the cronny at 2815fps!

72 grains of IMR4350, Federal 215 primer and a Hornady 225 grain runs across the cronny at 3000fps

Jimmy

A life of shemale porn and golf. Who could ask for anything more? -
I also go to the black community and give speeches in an effort to uplift the people. Someone out there has been reading their gay oriented newsletters!!

Dr. Ralph

So Dave, do you have way too much money or are you just crazy?

Jimmy is confused. He said he’s married to a transsexual and can not make up his mind is it the tits or the balls he is attracted to!

Ed J

Clay
How long is the barrel? 20 inches or 26 inches? That makes a difference.

Juice

Somebody is definately here talking about transees and it ain't me mothafu*^er. They're using my name.

Gunslinger

I wish I had the time, money and a place to shoot a thousand rounds a year, or better yet, to burn out a bbl on my 30-06's. Most of us don;t have the time, or take the time to pratice these days. I do get to go to the Rocky Mountains about every year or two and then I begin to pratice with cheapo ammo untill ready for the final test and zero's if the 0 is off. No questions need be ask, most hunters don;t pratice enough. I;ve been on hunts where a guy comes out with a new gun, scope, sling, etc. and tells the guide its bore sighted at 100 yds per the salesperson at Wal-marts??????. My, how the guide love this. I;ve also been on hunts where a older guy like myself has an old gun, sometimes with the stock taped together. This is the guy who fills his tags early, as he knows how to shot just by looking at his gun.Too many so-called hunters think a magazine of ammo shot is sufficient to kill a trophy, sadly it isn;t. I try to shoot at least l0 rounds per day for 3 months prior to my trips west. As last year I killed 2 animals in excess of 300 yds with one shot to each animal. That is beyond my "rather zone" of 200 yds, but the landscape in the western states will fool you, there- fore, by all means take a rangefinder and use if you have time. I prefer the buddy system, 2 guys hunting together. But sometimes its only you. Just make sure you shot for the Vitals and hold-tight. Then ease the trigger back and PRAY. Good luck and happy hunting. Enjoy the next hunt, as it could be your last.

Wu Yung Ho

"I try to shoot at least l0 rounds per day for 3 months prior to my trips west"

"I wish I had the time, money and a place to shoot a thousand rounds a year"

you a caucasian

Archibald MacLeish

Look, buddy, we got a union, see? We got us a solid, foursquare, rock-ribbed union and we ain't gonna pull no shifts, see? The Germans are coming to beat you up again. They should arrive around four-ish or so. Once they stomp your sniveling French asses and process your Muslim invaders, they are going to march on down to Israel and blister their little bleating bottoms, too. Then I suppose that they will stomp the Saudis and get all that sweet, light crude to impel their powerful Mercedes down their delightful autobahns...

Goat OrchestraSchizophrenia

We take over You soon. You see! We fix Hillary right away. Then your get free acupuncture and lifetime job for every american! You like! No more SUV. Never lay off! No more fatty meat. No more commute! No more mortgage! You live in big factory, make big quota, be happy!
China Make New World Order!




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