What kills barrel life on bigger magnums?

[Kennibear]

When fiftydriver speaks I tend to listen. Hard to argue with somebody who does this everyday.
Not too many years ago I was heavily into Title II stuff and you could burn out a barrel throat in a few minutes of pouring ammo through a machinegun. If you loaded up about 500rnds in mags and fed them one after another the barrel would glow. After cleaning it up an inspection of the throat showed it was shot out for anything other than ventilating hillsides and barns. Provided the barn wasn't too far away.

I've known about heating up a barrel for quite some time but there wasn't much you could do but wait it out. No fun just to sit still at the bench. Read about a wand hooked to a CO2 tank and blown through the barrel but it was so fast I wonder if it shocks the barrel, i.e. quenches it.


This is a barrel cooler my son and I built. Scrap PC fans @ $1 each (3) and a 12 volt gel cell from a computer UPS backup also sold @ the box stores for alarm systems for $25 new. The big hose is a dishwasher hose, same source. The small hose is scrap from the garage and fits the bolt size pretty close (about 5/8"). Two of the fans are stacked and feed the forward chamber. The third fan forms the third stage and pushed the pressurized air from that chamber into the hose. You need to build some pressure not just volume because your going to push the air down a rifle bore, hence the three stages.
It sits on the ground under the bench and we open the bolt to extract the fired round and push the small tube into the chamber and flick the switch. With 45 seconds of run time we keep a barrel that starts at 85F under 100F for five shots. This is for something like a 300 WinMag or 375 Ruger. There is a K type bead thermometer taped to the barrel over the chamber to track it. The air is filtered by a piece of 3M Scotchbrite pad cut to fit the back of the box.

You can watch the temp fall when you turn on the switch. Keeps the barrels cool and our investment in the guns from heading toward the target in the form of vaporized steel. It lets us test a lot more ammo in the course of a day at the range so it has paid for itself in that alone.

Some people may laugh... but I've got one and they don't!

KB

 

[ICANHITHIMMAN]

Using the trigger as a giggle switch repeatedly! A couple shots then checking conditions and letting things chill will go a long ways!

Lmao well,said sir well said as other said keep it cool and it will last a long long time, also just because your throat starts to error does not mean the barrel,is cooked it means you need to adjust your load.

 

[Greyfox]

Without getting too scientific the numerous barrels that I have gone through appear to definitely be effected by heat typically caused by rate of fire. My competition rifles that are used in the summer months with strings as high as 30 shot strings at 30 second intervals have half the life of those shot with cooling allowed between shots. Life is measured by accuracy fall off , from .25-.5MOA to .5 to.75MOA. generally, my 308 competition rifles see this fall off at 2200-2400 rounds. Throats erode .060-.120" with a R5 Milpec barrel, that is generally cleaned every 150-200 rounds. Shooting magnums at +3000FPS and the 6.5x284, accuracy seems to fall off at 800-1200 rounds. The low end, or worse for the Weatherby, Short mags, and other overbore designs, high end for the 7mm-300 standards. This is with cooling allowed between shots. Generally, heavier, lower velocity bullets seem to give better barrel life out of the magnums than high velocity, lighter bullets. Barrel quality also pushes life to one end or the other of the range. I'm sure some see better or worse life than I do. Overall, I think barrel life is a function of case/cartridge design, powder charge, shooting style/heat, barrel quality and cleaning procedure. I do keep a round count for all my rifles but generally don't get too hung up on barrel life with hunting rifles if the rifle performs well. For competition rifles, I don't want to have to change a barrel or rifle in the middle of the season. IMO.

 

[Fiftydriver]

When fiftydriver speaks I tend to listen. Hard to argue with somebody who does this everyday.
Not too many years ago I was heavily into Title II stuff and you could burn out a barrel throat in a few minutes of pouring ammo through a machinegun. If you loaded up about 500rnds in mags and fed them one after another the barrel would glow. After cleaning it up an inspection of the throat showed it was shot out for anything other than ventilating hillsides and barns. Provided the barn wasn't too far away.

I've known about heating up a barrel for quite some time but there wasn't much you could do but wait it out. No fun just to sit still at the bench. Read about a wand hooked to a CO2 tank and blown through the barrel but it was so fast I wonder if it shocks the barrel, i.e. quenches it.
View attachment 29092

This is a barrel cooler my son and I built. Scrap PC fans @ $1 each (3) and a 12 volt gel cell from a computer UPS backup also sold @ the box stores for alarm systems for $25 new. The big hose is a dishwasher hose, same source. The small hose is scrap from the garage and fits the bolt size pretty close (about 5/8"). Two of the fans are stacked and feed the forward chamber. The third fan forms the third stage and pushed the pressurized air from that chamber into the hose. You need to build some pressure not just volume because your going to push the air down a rifle bore, hence the three stages.
It sits on the ground under the bench and we open the bolt to extract the fired round and push the small tube into the chamber and flick the switch. With 45 seconds of run time we keep a barrel that starts at 85F under 100F for five shots. This is for something like a 300 WinMag or 375 Ruger. There is a K type bead thermometer taped to the barrel over the chamber to track it. The air is filtered by a piece of 3M Scotchbrite pad cut to fit the back of the box.

You can watch the temp fall when you turn on the switch. Keeps the barrels cool and our investment in the guns from heading toward the target in the form of vaporized steel. It lets us test a lot more ammo in the course of a day at the range so it has paid for itself in that alone.

Some people may laugh... but I've got one and they don't!

KB

Most impressive setup!!! I have always been a bit nervous about the fast barrel coolers out there as well. Just do not like thermo shocking metal. Just not a good idea in my mind.

Congrats on the creative solution!!!

 

[Fiftydriver]

Without getting too scientific the numerous barrels that I have gone through appear to definitely be effected by heat typically caused by rate of fire. My competition rifles that are used in the summer months with strings as high as 30 shot strings at 30 second intervals have half the life of those shot with cooling allowed between shots. Life is measured by accuracy fall off , from .25-.5MOA to .5 to.75MOA. generally, my 308 competition rifles see this fall off at 2200-2400 rounds. Throats erode .060-.120" with a R5 Milpec barrel, that is generally cleaned every 150-200 rounds. Shooting magnums at +3000FPS and the 6.5x284, accuracy seems to fall off at 800-1200 rounds. The low end, or worse for the Weatherby, Short mags, and other overbore designs, high end for the 7mm-300 standards. This is with cooling allowed between shots. Generally, heavier, lower velocity bullets seem to give better barrel life out of the magnums than high velocity, lighter bullets. Barrel quality also pushes life to one end or the other of the range. I'm sure some see better or worse life than I do. Overall, I think barrel life is a function of case/cartridge design, powder charge, shooting style/heat, barrel quality and cleaning procedure. I do keep a round count for all my rifles but generally don't get too hung up on barrel life with hunting rifles if the rifle performs well. For competition rifles, I don't want to have to change a barrel or rifle in the middle of the season. IMO.

I would agree that the lower velocity rounds do seem to offer longer barrel life but again, it has more to do with actual bore temps then anything else.

Slower rounds tend to use powders that generally burn mostly in the case compared to lower expansion ratio designs where a significant amount of the powder charge is burnt in the throat and first portion of the barrel. When this happens, it simply takes longer for the bore temp to cool off.

Have tested different neck length designs, shoulder angle designs and I have never seen any of these make any real difference to throat life if the barrel was kept cool.

 

[Fiftydriver]

One test I did many years ago that pretty much solidified my opinion on what keeps a barrel shooting well is when I tested some forward ignition systems in some of my wildcat chamberings.

Not to get to detailed, forward ignition systems use a brass tube connected to the flashole in some manner that carries the primer flame to a position in the powder charge just under the base of the seated bullet. When the primer is ignited, the hot primer gases ignite the powder just behind the base of the bullet and the powder burns progressively from the front of the case to the rear.

When you fire a case in a modern rifle, the ejected cases are hot at first but not DRAMATICALLY so and the first 1/3 of the barrel heats up quickly.

With forward ignition being used, the ejected cases are NOTICABLY hotter then conventionally ignited cases but the bore simply does not heat up early as fast. Why, because the only thing going through the case neck is gas, no burning powder. As such, with nearly 100% of all the powder charge burning INSIDE the cartridge case, the case insulates the bore from the heat generated and the bore stays very cool.

One test was with my 7mm Allen Magnum. In a sporter weight rifle, with conventional ignition, three rounds and the barrel was to hot to hold with a bare hand for more then a few seconds. With forward ignition, you could shoot 9 shots before the barrel temp reached the same temp as with conventional ignition systems.

Barrel life also increased dramatically, 2-3 fold!!!

You do have to change what powders you use for a given chambering because you are no longer PUSHING the weight of the powder charge and pushing ONLY the bullet weight. As such, you need to go to a slightly faster burning powder. In the end however, this system frees up pressure dramatically, again because your not pushing the powder charge throught the throat and in most tests, 100-150 fps performance increase was realized with same chamber pressure.

With all these advantages however, its a PITA to fit each case with a flash tube and there is always a chance the flash tube could come loose and go down the bore. This is a liability issue I just could not live with so I stopped this testing until I figure out a better design that positively locks the flashtube in the case 100% of the time.

It did however prove that bore temp was dramatically reduced and as such, barrel life exploded!!! Did not seem to matter what powder was used, ball, stick, it all showed similar results in the end. Also did not really matter what the case capacity was, in fact, the larger the case capacity was, the larger the difference in barrel life between conventional and forward ignition.

Was really amazing results, just need to figure out the reliability of the system to bring it to the market.

 

[hemiford]

I gave thought to using a small rag of some sort, soaked with light oil,
and kept in a chilled picnic basket. After each firing or two, just lay the
chilled rag on the barrel to wick some heat out. I figured the rag would
not be cold enough to alter the metal's temper, but by the same token,
not work lightning fast either in removing heat.

 

[scsims]

Pure and simple, bore temperature kills throat life. It really does not matter how much powder you burn in a chambering or how little, its how hot the barrel is and if you continue to shoot the rifle that will determine how long or short your rifle lasts.

Some of my wildcats are pretty extreme but if you keep the barrel cool and clean, they last for a suprising long time. On the other side of the coin, if you take a chambering with much less capacity, get the barrel hot and keep shooting, it will erode a throat much more quickly then a larger capacity chambering that is properly used and cared for.

Muzzle velocity has very little to do with bore wear.

Powder type also has very little difference. In the end, its how hot the bore gets and if you keep shooting the rifle. This may mean you need to keep shot strings to less then three shots and allow barrel to cool between each which is exactly my recommendation for all my customers using my extreme performance rifles.

Simply comes down to keeping the bore clean and most importantly, keep it cool.

Now, some barrel steels withstand barrel wear better then others. The harder stainless steel in cut rifled barrels tends to offer slightly longer throat life then a button pulled barrel.

Throat design also is a factor. The tighter the throat and to some degree, the shorter the throat, the longer the accuracy life of a barrel will be but again in the end, bore temp while firing is BY FAR the most important factor in barrel life.

Keep em clean and cool and they will last much longer then most would ever believe.

Hey Kirby, don't want to derail this thread, but could you elaborate on how cleaning helps prolong the accurate life of the barrel? It seems I read more that people don't clean their bores until accuracy drops off...... could be hundreds of rounds.

Should you only use a powder and carbon solvent until accuracy drops off then attack the copper, or just keep it clean with somthing like Bore Tech between range trips?

 

[Fiftydriver]

Hey Kirby, don't want to derail this thread, but could you elaborate on how cleaning helps prolong the accurate life of the barrel? It seems I read more that people don't clean their bores until accuracy drops off...... could be hundreds of rounds.

Should you only use a powder and carbon solvent until accuracy drops off then attack the copper, or just keep it clean with somthing like Bore Tech between range trips?

With the chamberings I deal with most often, carbon fouling is as big of a problem as copper fouling is. If carbon builds up, your accuracy will drop off.

Also, any fouling in the bore can attract moisture and cause the finish of the bore to degrade from corrosion, that is always a bad thing.

Cleaning really does not increase bore life per say but keeping your bore clean reduces the chance that dirt, dust and grit can get into your receiver, chamber and bore. All three can reduce the life of the entire weapon system if left in the rifle while in operation.

 

[Mikecr]

I know it's swimming upstream to say, but I thinks it's a bad idea to leave bores fouled for extended periods. I also think it's a bad idea to shoot many rounds between cleanings(100-200).

For ACCURATE barrel life, we need to control carbon.
Ignoring it for the sake of stable fouling, is like ignoring an infection -until it takes you out of service.
By then, it's gonna take more than a minor antibiotic to recover. It's gonna mean stopping everything until you get that carbon out of there.
And if you don't, like many don't, and you continue shooting, you're shortening your barrel life. This, because bore constriction continues to develop -faster.

The most practical way for us to extend barrel life, for real, is melonite treatment. If I shot a lot of powder like you guys, I wouldn't hesitate for 1 second on getting this done for my barrels.
All my future barrels will get it, the moment I know it shoots.

 

[Kevin Thomas]

I'm a bit surprised that no one has mentioned this so far, but in my experience, one of the primary factors that goes into the faster destruction of a barrel is bullet weight. Simply put, heavier bullets are harder than lighter bullets, other factors being equal. The reason for this seems pretty simple, and that is basically dwell time. The heavier bullets have more inertia to overcome as the bullet begins moving down the barrel. During that time, the hot powder gases and very high pressures spend more time doing their damage to the throat area than they would with a lighter bullet which gets out of the way a good bit more quickly.

There's other factors at work as well, but in a straight apples to apples comparison, that's a huge one. Having washed out several hundred barrels over the years, there's no doubt in my mind that bullet weight is a (or more likely, "the") major factor in bore life.

 

[Mikecr]

No single factor passes all tests because it's a combination.

A competitive 6PPC -vs- 338

 

[Michael Eichele]

I'm a bit surprised that no one has mentioned this so far, but in my experience, one of the primary factors that goes into the faster destruction of a barrel is bullet weight. Simply put, heavier bullets are harder than lighter bullets, other factors being equal. The reason for this seems pretty simple, and that is basically dwell time. The heavier bullets have more inertia to overcome as the bullet begins moving down the barrel. During that time, the hot powder gases and very high pressures spend more time doing their damage to the throat area than they would with a lighter bullet which gets out of the way a good bit more quickly.

There's other factors at work as well, but in a straight apples to apples comparison, that's a huge one. Having washed out several hundred barrels over the years, there's no doubt in my mind that bullet weight is a (or more likely, "the") major factor in bore life.

I'm glad you indicated a straight apples to apples comparison because if dwell time was the only factor, a 300rum running 150s would out live a 308 running 150s. But we all know the reality here.

I tend to agree with you. I recently performed an 'arc flash study' for some electrical systems recently. One thing I learned was that the intensity of an arc flash (an electrical fault caused by the ionization of air around electrical terminals or busses which is hotter than the surface of the sun) compared to the severity are two totally different things. Intensity is how big and hot the flash but the severity accounts for the duration of the arc. An arcing current of 4000 amps with a .04 second duration is A LOT less severe than an arcing current of 2000 amps that lasts .4 seconds. Time here is the difference between curable 2nd degree burns to humans verses non curable burns. I guess the same principal could be applied to the inside of a barrel.

I also know from first hand experience that carbon rings kill barrels. These will definitely increase pressure. You have to keep caked on carbon to a minimum. Especially in the throat area which can and will dramatically increase pressure when the bullet slams into that tight spot. The more 'over-bore' the cartridge, the faster and more severely the carbon rings develop. They don't come out with standard cleaning practices either so when you think your barrel is clean, you may still have remnants which just keep getting worse.