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Decrease throat erosion with longer barrels?

 
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  #8  
Old 06-08-2013, 08:22 PM
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Re: Decrease throat erosion with longer barrels?

IMHO, longer barrels only help you gain velocity by giving you more burn area volume to burn more powder (more of a slower burning powder) thus increasing your velocity potential. All else being equal, I feel adding barrel length only adds friction that slows bullets down. Imagine a 100 foot long barrel chambered in 308 win. Would the bullet even exit the barrel?

If you start with a 30" barrel, work up a load that is optimum for your barrel/bullet/powder combo, then cut 2" off, you will loose some velocity. Adding more of the same powder may bring your velocity up but the powder/barrel length/etc...is no longer optimal. Using a faster powder solves this problem. You get your velocity back and optimize your load/barrel relationship. This is just an illustration of my point. All this said, shortening your barrel and using faster powders may be the way to increase throat life as adding barrel length increases the time the bullet is in the barrel adding to the duration of heat and flame exposure to the throat. Honestly, I think you're barking up the wrong tree.
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Originally Posted by Broz View Post
Please just answer one very simple question. Why would anyone shooting long range load a low BC , low SD 168 gr offering in a 300 win???????

My answer to this is. The only reason is to make the 7 RM look good. There is no other reason.

Jeff.
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  #9  
Old 06-08-2013, 10:20 PM
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Re: Decrease throat erosion with longer barrels?

Quote:
Originally Posted by Michael Eichele View Post
IMHO, longer barrels only help you gain velocity by giving you more burn area volume to burn more powder (more of a slower burning powder) thus increasing your velocity potential. All else being equal, I feel adding barrel length only adds friction that slows bullets down. Imagine a 100 foot long barrel chambered in 308 win. Would the bullet even exit the barrel?

If you start with a 30" barrel, work up a load that is optimum for your barrel/bullet/powder combo, then cut 2" off, you will loose some velocity. Adding more of the same powder may bring your velocity up but the powder/barrel length/etc...is no longer optimal. Using a faster powder solves this problem. You get your velocity back and optimize your load/barrel relationship. This is just an illustration of my point. All this said, shortening your barrel and using faster powders may be the way to increase throat life as adding barrel length increases the time the bullet is in the barrel adding to the duration of heat and flame exposure to the throat. Honestly, I think you're barking up the wrong tree.
Michael,

I understand your logic and if it's true, then if I shorten a barrel to say 20 inches then I should have longer barrel life. Am I applying your logic correctly?

When looking at specifications at the Savage website, I see barrel lengths of 26, 28, 29 & 30 inches for varmint and target grade rifles. Using your reasoning should I assume all lengths above 26 inches will erode barrels faster as the lengths increase?
Now I'm potentially confused in an area where I wasn't before.:-)
I do appreciate your input.

Fortunately I'm not in a hurry to get this settled in my mind. I just like to venture into areas of extreme thoughts at times.

If you have anymore thoughts, chime in.

Spencer
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  #10  
Old 06-09-2013, 01:02 AM
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Re: Decrease throat erosion with longer barrels?

Most barrel erosion occurs in two areas of the barrel: the throat and the muzzle. The throat gets the brunt of the abuse through heat and chemical. The muzzles tends to wear and becomes less round and more "fish eye" in shape. As a general rule, bullets will gain about 25 fps for every inch added. But this is only true for barrels in the 20' to 26" range. After that, it becomes a game of diminishing returns. It can actually become a detriment and slow the bullet down if the barrel is too long. Dan Lilja wrote a pretty interesting article on the subject a while back:

Lilja Precision Rifle Barrels - Articles: Barrel Lenghts and Velocities in the 338/378 Weatherby Magnum

Both the 308 and the 30-06 get great barrel life and throat wear. You begin to see some shortening of barrel life in the 300 Win Mag. The 300 Ultra Mag shows even more. A max load for a 180 gr. bullet in a 308 is approx. 48 gr. of Win 760 @ 2600 fps. A max load for a 180 gr. bullet in a 30-06 is approx. 56.5 gr. of Win 760 @ 2800 fps. Max loads in 300 Win Mag require about 70 gr. of powder, while the 300 RUM requires 90-95 gr. to reach max velocity with a 180 gr. bullet.

My point is this: you need substantial drops in powder to begin to realize any saving in the area of throat erosion. Even the 30-06 burns 18% more powder, but does not suffer from shorter life due to barrel erosion. Most starting loads in reloading manuals for any of the above calibers are only 5% under the listed max loads. To gain any appreciable decrease in barrel wear (such as between the .308 and the 300 Win Mag), you are looking at a decrease in powder of 30% or more. It just isn't practical in light of other factors mentioned previously.
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  #11  
Old 06-09-2013, 05:33 AM
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Re: Decrease throat erosion with longer barrels?

Quote:
Originally Posted by azsugarbear View Post
Most barrel erosion occurs in two areas of the barrel: the throat and the muzzle. The throat gets the brunt of the abuse through heat and chemical. The muzzles tends to wear and becomes less round and more "fish eye" in shape. As a general rule, bullets will gain about 25 fps for every inch added. But this is only true for barrels in the 20' to 26" range. After that, it becomes a game of diminishing returns. It can actually become a detriment and slow the bullet down if the barrel is too long. Dan Lilja wrote a pretty interesting article on the subject a while back:

Lilja Precision Rifle Barrels - Articles: Barrel Lenghts and Velocities in the 338/378 Weatherby Magnum

Both the 308 and the 30-06 get great barrel life and throat wear. You begin to see some shortening of barrel life in the 300 Win Mag. The 300 Ultra Mag shows even more. A max load for a 180 gr. bullet in a 308 is approx. 48 gr. of Win 760 @ 2600 fps. A max load for a 180 gr. bullet in a 30-06 is approx. 56.5 gr. of Win 760 @ 2800 fps. Max loads in 300 Win Mag require about 70 gr. of powder, while the 300 RUM requires 90-95 gr. to reach max velocity with a 180 gr. bullet.

My point is this: you need substantial drops in powder to begin to realize any saving in the area of throat erosion. Even the 30-06 burns 18% more powder, but does not suffer from shorter life due to barrel erosion. Most starting loads in reloading manuals for any of the above calibers are only 5% under the listed max loads. To gain any appreciable decrease in barrel wear (such as between the .308 and the 300 Win Mag), you are looking at a decrease in powder of 30% or more. It just isn't practical in light of other factors mentioned previously.

You & Michael have given me a lot of information to think about. Because of an extreme A.D.D. condition, it takes me a bit longer to retain new information. Been this way since childhood.
My new rifle will be chambered for the 22-250 & I know I'm not I'm the same league as the guys shooting big bore way beyond 500 yards.
I want to go to that link you provided & read more. This will help clarify what the two of you have have already told me. I did a number of searches online trying to use different phrases to come up with some leads, with no results. I wasn't even sure I'd get any responses here.

It appears as though even 4 inches increase in barrel length can't compensate for any realistic drop in charge weight. Another case of diminishing returns
Since birth (1941) I've always needed to understand things to a degree beyond what most people accept. I don't just want to know the answer, I want to know why. I've never been able to let go of that way of thinking.
Most people look ay me and think or say, "WTF are you talking about?"
Clarification in my mind doesn't happen fast for me, but I don't let go until it does.
My mind has a pattern of wandering off in tangents, so there's more than a fair chance I'll be back with more questions or thoughts.

Thanks again for the time you two have been willing to take with me.

Spencer
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  #12  
Old 06-09-2013, 06:28 AM
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Join Date: Sep 2011
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Re: Decrease throat erosion with longer barrels?

Of course throat erosion will decrease when shooting a low pressure load, compared to hot loads. If your velocity is a constant, a longer barrel and slower burning powders will give you the same velocity at a lower pressure, than a hot load with fast burning powders in a shorter barrel.
You are asking about a .22-250.
This case has about the same volume as a .30-30.
A .22-250 chambered 30" barrel has about the same volume as a 17" .30-30 chambered barrel. Does someone want to say 17" is too long for a .30-30?
Changing barrel length means always playing with volume, the smaller the caliber your using, the slower pressure will decrease as the bullet runs down the barrel, because volume doesn't increase as fast as in a bigger bore.
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  #13  
Old 06-09-2013, 06:52 AM
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Re: Decrease throat erosion with longer barrels?

If you are trying to reduce throat erosion, then melonite the barrel. Cost is $100 and way longer barrel life
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  #14  
Old 06-09-2013, 09:38 AM
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Location: Central AZ
Posts: 881
Re: Decrease throat erosion with longer barrels?

+1 on the meloniting.

Tracy,

Regarding your need to understand the "why" of things - that's the reason most of us are here on LRH. And just when you think you have a handle on things, a new line of reasoning comes up and you start the process all over again. We are here because we like to be challenged...we like to learn.
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