Hello all, I have been lurking around here for awhile just enjoying the information. Now I have a question. I have been reloading for 30 years for dozens of cartridges and some wildcats. My question is this: I am loading for a .257 Weatherby. We all know this particular cartridge is hard on barrels. If I am loading some reduced loads for shooting and practicing with this rifle, am I better off using a volume of slower or faster burning powder to achieve the same velocity? Which would be easier on the bore? Possibly I am over analyzing this but I was curious and thought I would ask a group of seasoned shooters. Thanks in advance.

I've played with both and really never saw what I felt was a difference. Use what you want and don't overheat the barrel. Single based powders ususally will generate less heat.

What really accelerates the destruction of a barrel in an overbore like the 257Wby is trying to get that last fps and heat. Drop back a couple 100fps kept it cool and enjoy.

All my research has shown that velocity and pressure are the key ingredients to barrel wear. backing off to a minimum load with any powder will ease the wear significantly. That said the mildest load is usually achieved the minimum charge of the fastest burning powder listed in the books.

Velocity has almost nothing to do directly with barrel wear in high intensity cartridges. The place that gets the most wear by far is the throat where the velocity is the slowest - it will wear out much much sooner than the muzzle end of the barrel where the velocity is highest. Barrel erosion is caused by high heat and large volumes of gas, the more of either or both and the worse the throat erosion will be. Going to a faster powder reduces the volume of gas but pressures/temperatures can still be high if decent velocities are desired. Using a slower powder can reduce the pressure and temperature but produces more volume of gas to funnel down the small bore. But with the .257 Weatherby slow powders are normally used to obtain high pressure/velocity loads anyway. Reducing a slow powder very much may risk pressure excursions.

Perhaps the best method is to use the fastest powder recommended for the cartridge and reduce it to starting levels. This reduces both gas volume and pressure/temperature but velocity loss can be high, down to .257AI speeds.

OTOH, simply shooting slowly and not allowing the barrel to heat up can extend barrel life a lot even with maximum loads. One of my .257 Weatherbys has almost 1000 rounds through it, and it still shoots about as well as it did when new. I have been very careful to shoot only 3-shot groups most of the time, and let the barrel cool off between groups. This way I get the velocity I paid for with the .257 and longer barrel life too.

Nosler #5 agrees when shooting the very similar .264 Winchester Magnum: "We have found surprisingly long barrel life can be expected, even with full power loads, provided the shooter takes care not to overheat the barrel and employs frequent bore scrubbings"



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quote:

Velocity has almost nothing to do directly with barrel wear in high intensity cartridges

Actual velocity no. Pressure and heat to generate the velocity yes.

rate of fire and barrel heat are your big enemies. That said, if you shoot one high intensity round and then let the barrel cool, you are doing less damge than if you shot several moderate loads rapidly.
I'm not sure but possibly going to a lighter bullet might also help reduce pressure and heat.

Thanks for the information. Let me step back and share my plan. I have a custom built rifle. The chamber and throat are not "Weatherby" freebore. Because of this I am able to use less powder to begin with to obtain respectable velocities. I currently use the Barnes 100 grn. TSX. My intention is to use the Berger 115 VLD at about 3100-3200 FPS. This will give me similar trajectories. I certainly don't consider these velocities high for the cartridge/bullet combination. I have always shot slowly and don't anticipate taking on Praire Dog towns with this rifle. It gets cleaned every 15 rounds,as I have noticed accuracy falls off about there. Again thanks for the input.

Kinda moot if you shoot a lot. Then barrels are just another component that has to be replaced periodically. It's an issue with me for certain rifles because of heirloom status or rarity but I expect to have to rebarrel most of my rifles at least once. So I load for performance without consideration for much else in the generic shooting machines.

quote:

Originally posted by TX Nimrod:
Velocity has almost nothing to do directly with barrel wear in high intensity cartridges. The place that gets the most wear by far is the throat where the velocity is the slowest - it will wear out much much sooner than the muzzle end of the barrel where the velocity is highest. Barrel erosion is caused by high heat and large volumes of gas, the more of either or both and the worse the throat erosion will be. Going to a faster powder reduces the volume of gas but pressures/temperatures can still be high if decent velocities are desired. Using a slower powder can reduce the pressure and temperature but produces more volume of gas to funnel down the small bore. But with the .257 Weatherby slow powders are normally used to obtain high pressure/velocity loads anyway. Reducing a slow powder very much may risk pressure excursions.

Perhaps the best method is to use the fastest powder recommended for the cartridge and reduce it to starting levels. This reduces both gas volume and pressure/temperature but velocity loss can be high, down to .257AI speeds.

OTOH, simply shooting slowly and not allowing the barrel to heat up can extend barrel life a lot even with maximum loads. One of my .257 Weatherbys has almost 1000 rounds through it, and it still shoots about as well as it did when new. I have been very careful to shoot only 3-shot groups most of the time, and let the barrel cool off between groups. This way I get the velocity I paid for with the .257 and longer barrel life too.

Nosler #5 agrees when shooting the very similar .264 Winchester Magnum: "We have found surprisingly long barrel life can be expected, even with full power loads, provided the shooter takes care not to overheat the barrel and employs frequent bore scrubbings"



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I agree with everything you've said, and I would also like to add that the type of powder used has a very dramatic effect on throat erosion.
Single base powders produce more gas and burn generally hotter than double base powders, which by nature produce more energy for the same density. This fact tends to be easier on barrel throats, it's the 'torch' effect that does the damage.
As we all know, powders begin to burn progessively, and then when the heat and pressure rise to a point they begin to burn digressively, well before the muzzle. It is this digressive burning that raises pressure inside the barrel, keeping the flame front at or just past the throat of the rifle longer, if the gas is initially cooler, as with double base powders, it will slow throat erosion dramatically. Ball powders seem to have the same effect, whether double base or not.

There is also the belief that a lighter bullet and faster powder will be easier on barrels, unfortunately this is not so. Pressure rises quicker with faster powders and light bullets, and therefore so does the gas and heat, which is likely to cause more throat erosion than a heavy bullet/slow powder combo.

Double base powders will definitely reduce the effects on throat erosion, so too will slow fire when sighting in or developing a load, a hot barrel is just asking to be 'burned up' early!

Cheers.

quote:

Originally posted by 416RigbyHunter:
... Double base powders will definitely reduce the effects on throat erosion...

Huh??

- mike

Someone will probably fly off the handle telling me I have no experience in this, but my secondhand information is relevant to the question so I'll give it anyway.

A national competitor in the US who shoots 243 Win and 6mm Wildcats exclusively has pointed out to me that he uses very slow single based propellant only (shooting mostly 107gr SMK's). This he says has given him the best barrel life when coupled with a thorough cleaning regimen.

His comment was that in his experience the powder was the primary determining factor in barrel life in the 243(which he shot exclusively for some time).

This seems to be the anecdotal evidence that I have received elsewhere too.

These guys are comparing similar performance levels in their rifles, so I think they make worthwhile comparisons.

I'm repeating this as I was told and if you disagree, fine, I won't defend what is not my opinion, but I will respect and go with what I was told by this experienced and extremely knowledgeable gentleman who has spent a lot of money testing these things. Hopefully this will save me from having to find it out for myself!

While common terms are 'wear' and 'erosion' the mechanism is actually the absorbing of carbon from the hot burning powder.This higher carbon area of the barrel then cracks on subsequent cooling .The condition worsens as the shooting continues.
Keep it cool !

Erosion is a big problem, I have slowed the barrel wear by slowing down the bullet. Why do you have to be going full blast when you are only shooting on paper??? Hunting is when you need the max. from your ordnance. So just change your glass settings from slow to fast bullets and maybe the results you are looking for may happen. Works for me.

My MK5 has probably 1000 or 1500 rounds on it,I got it before I wrote everything down, and it went from a 1.5 to 3 in. with any load. It needs rebarreled. Its a hot rod so I ran it like a hot rod max. every shot. Now it sits in the safe waiting for a new barrel.

As you mentioned that it is not your intent to use your .257 Weatherby for a prairie dog shoot, is there going to be a shooting opportunity where you will be throwing a lot of lead fast down the tube?

If your application for that shooter is to hunt big game with I would go ahead and just load it up the way you want and not be concerned about erosion. I've got some hunting rifles that I may shoot only 10-15 times a year and yet other smaller calibers that I may shoot 600 rounds a year. And if the barrel needs replacing, as was mentioned, it could just be viewed as another cost of the sport.

If it's for some target shooting application that would be another story and cooling would seem to be the solution.

I always wanted to have a .257 Weatherby as I was growing up and dreamed about all the hunting of critters big and small that I could do with it. Good luck and enjoy it.

quote:

Originally posted by mho:

quote:

Originally posted by 416RigbyHunter:
... Double base powders will definitely reduce the effects on throat erosion...

Huh??

- mike

Mike,
As I stated, double base powders will slow throat erosion due to less gas volume/heat produced.
I have first hand experience with this in my 300WM F-Class rifle. I have been able to extend usable barrel life by switching to very slow for calibre double base powders, RE25 is the powder in question. I have kept detailed records for 3 barrels on this rifle, and I have had 500 more rounds through it using RE25 alone.
Previous powders used were H4350 and H4831 in the other barrels.
It's also worked in other high intensity cartridges I load for, ie, 22-250AI, 25-06, 264WM, 270Weatherby and 300Weatherby. I also use the same idea on other less intense cartridges and barrel life is long.
I have a bore scope and keep a close watch on my throats, I do not 'chase the lands' as others do, but I increase the powder charge to get the same ballistics as my throats wear, this also seems to keep throat erosion at a minimum, until a certain level is reached and no procedure will halt it's progress.

Cheers.

quote:

Originally posted by 416RigbyHunter:
Mike,
As I stated, double base powders will slow throat erosion due to less gas volume/heat produced.
I have first hand experience with this in my 300WM F-Class rifle. I have been able to extend usable barrel life by switching to very slow for calibre double base powders, RE25 is the powder in question. I have kept detailed records for 3 barrels on this rifle, and I have had 500 more rounds through it using RE25 alone.
Previous powders used were H4350 and H4831 in the other barrels.
It's also worked in other high intensity cartridges I load for, ie, 22-250AI, 25-06, 264WM, 270Weatherby and 300Weatherby. I also use the same idea on other less intense cartridges and barrel life is long.
I have a bore scope and keep a close watch on my throats, I do not 'chase the lands' as others do, but I increase the powder charge to get the same ballistics as my throats wear, this also seems to keep throat erosion at a minimum, until a certain level is reached and no procedure will halt it's progress.

Cheers.

I hear you, and I have to admit that I have no way of either proving or disproving that double based powders are "erosion intensive". I have seen a ton of references to double based powders being potentially (more) erosive in gun literature (incl. gun rags) in the past. E.g. the VihtaVuori double based powders seem to have acquired a bad rap for this - correctly or not. See past discussions in here.

Now one of the problems with discussing erosive properties of a particular (group of) powder(s) is that people seem to have widely varying experience. One person will claim A while another will totally disagree and claim B is right... So it is near impossible to get a handle on what is fact and what is fiction.

- mike

The armaments engineering literature and textbooks are pretty unanimous about the causes and mechanisms of barrel erosion.

They broadly group causes in 3 categories. 1. Heat energy erosion, 2. Chemically mediated erosion (The effect of interaction of the chemical products of combustion on steel) and 3. Mechanical erosion. ( This includes jetting and scrubbing by solids in the propellant )

Of the 3 heat energy is the major contributor by far.

The absolute caloric content of the propellant and the absolute adiabatic flame temperature is by far the major contributor. This data is available on each and every propellant. It's akin to a welding torch, the more BTU's the hotter the flame the better it cuts.

In simple terms:

The more calories per mass unit of propellant , thus single vs double base and triple base propellants) the greater the erosion, the hotter the flame at point of combustion, ie more in charge weight is hotter than less. That is why in simple terms a large charge weight of propellant all else equal leads to more erosion.

The issue of Slow vs fast has to be seen in proper context. The combustion cycle, as a function of time, the difference in time of fast vs slow propellents is negligible. The total exposure time in the bore difference is in the order of fractions of a milliseconds. The combustion time of a cartridge loaded with a fast or slow powder is about the same on a time scale, the difference between "slow and fast" is not how fast the cycle takes but at what point in the barrel "burnt" occurs. In Fast the position of "burnt" is close to the throat in slow "burnt" occurs somewhere down the bore. The importance of this in gun design is obvious as it effects peak barrel pressure and projectile base pressure just prior to projectile egression from the bore.

In large gun ballistics and design the position of "burnt" determines the dispersion of velocity so that as a rule long range guns are designed to shoot "fast" propellants, ie position of burnt close to the throat and high velocity, relatively less accurate guns such as anti tank guns which rely on high velocities but are shot at close range ( 2000 and 3000 m ) use "slow" propellants with large velocity dispersion. Precision at long range is velocity dispersion dependent .

"burnt" referring to that point in the cycle where all of the combustable propellant is consumed.