Barrel life... the whats / whens / wheres / whys / and hows

[nasem]

Everytime I read about barrel life, its confusing as heck.... everybody has a different opinion.  Some say this XYZ round has a barrel life of 1200 rounds, other say "nope, you can get atleast 5000+"

I am trying to underestand What they are talking about here, I am trying to research about the barrel life of a 243 win (not for competition shooting, but more for a varmint long rang gun)

I am also trying to find out when barrel life starts to degrade or "wear out".  Again this is in regards to a typical caliber like the 243.

Also, where does the 'barrel wear' starts to usually develope, is it really the throat?

And finally, the biggest question of them all.... why oh why do barrels wear out and how do you prevent them.  I have read that you can prolong a 243 barrel life to well over 2000+ rounds if you use slow burning "cold" powders (not sure you can get a cold powder).  Keep in mind that I am new to reloading so any suggestion you might have about powders, remember to keep it simple

thanks

[gunnut69]

Wear in such an environment as a rifle bore is expected! Firstly there are the tremendous stresses and the heat generated by the friction of the bullet. Then the super heated air laden with carbon granules that is what the powder becomes.. sort of a sandblaster with the heat of a aceytelene torch... Lead bullets (not jacketed) tend to wear the least. Partly I'm sure because of the lower velocities to which they are loaded and partly because they are soft and lead is fairly lubricious or slick. A 22 long rifle bore will last for tens of thousands(some say even more) if maintained correctly. Allow the barrel to cool between shots. If the bore starts out the firing cycle at frying heat the damage each shot does will be greater. The more burned powder is funneled down the bore the faster it will wear.. Stainless is more resistant than caarbon steel but will still wear out.. Straight cased rounds because they don't create the overbore extremes of bottle necked rounds tend to last longer. There has been some talk of the use of ball powder or other slow burning rate powders to presserve barrel life as they spread the heat out a bit down the bore. I have not seen this test to any extent in hunting rifles but in automatic weapons there is a difference. Hard chrome plating the bore and chamber can also lengthen barrel life..  A 243 can last differing times depending on how its used and what its used for and how it's maintained. Most will last a hunter for a lifetime but a new one can be destroyed in a day or 2 on a prairey dog town.  A couple of shots perhaps 3 is about all that can be taken before it should be allowed to cool.. How do you know when a barrel is worn out? When the barrel no longer performs to what you expect from it.. For a deer hunter that might be a lot different than a target shooter or long range varmiter..  Another tidbit, light high velocity bullets seem to hurt a bore more than slower heavier bullets even though they burn roughly the same powder amounts.. I would guess its the friction but don't know. If you've access to a bore scope the throat of a rifle is an interesting place. They tend to look really bad but the diameter of the throat will also change. This can be measured by the differing seating depth to which a bullet falls into the throat of the bore. It will change as the throat erodes. Seating bullets out to match  this erosion is sometimes helpful in keeping the accuracy up. Sorry for the long rambling thread but I can't seem to get really focused tonight.. One last thought, a man I trust a lot said once that more bores were ruined by improper cleaning than by shooting..

[Brithunter]

Actually according to an experiment by Norma the bullet itself causes almost no wear    It's the burning powder which causes the damage.

   How did they discover this ................................................ well they took a bushel of bullets and fired them down a barrel after carefully measuring it  so they could check wear. The bullets were powered by compressed air. After several thousand bulelts they checked the barrels bore and again measured it and found virtually not difference in the measurements. Velocity of the compressed air fired bullets was roughly equal to normal ammunition so their conclussion is that it's the heat and chemical reaction that causes the wear.

    Now where did I read this why in an ammunition catalogue from Norma of course which I still have somewhere. No I don't know where as a lot of my stuff is still packed up after the move and until I get the workshop built sometime next year I will not have the room to sort it out 

[iiranger]

A number of years back, I read it in The Rifleman, the NRA did an article on barrel life. The experts seemed to agree, then anway, that the major cause of barrel "wear out" was the hot powder gases. Powder burns. With each shot the steel inside the barrel is exposed to hot gases. Some are nitrogen based... nitric oxides... The surface molecules of the steel react with the gases and become brittle, like the dried, clay chips on the surface of a lake bed. Next shot and the "reacted, brittle molecules" are scraped off by the passing bullet.

The rest is details. You work at low pressure, shotguns, low pressure pistols, black powder, .22 RF and a barrel lasts almost forever unless damaged otherwise. --Rust. Cleaning rod used wrong. Etc. And, I suspect, that lead bullets are much less effective scraping off the chips leaving them to protect during the next shot... Then there is the "grease" lubes, waxes, etc. Mr. Donaldson wrote of using a wax wad in his .220 Swift and having accuracy thru 10,000 rounds. Others have told me that Mr. Donaldson enjoyed nothing more than Mr. Donaldson...

Other end: 2 parts. i). Rapid fire. Machine guns go thru lots of barrels 'cause the process goes fast and the barrel stays hot.  In some cases the barrels get hot enough to "sag" or so I am told by air field workers about military machine guns on 'chopters.

Compare the "action" in a prairie dog town... Poor barrel and no tax money to replace it...

 ii). The huge cases working at top pressures. Burn more powder, cook more steel, lose more steel from the barrel with each shot.

Equally obviously, the muzzle where gases are alot cooler than in the burning area will last alot longer than the throat where the hottest gases "cook the steel" the longest. And the reason that the rifling, sticking up, gets "worn" / "rounded" in the throat fastest.

I knew a man, good gunsmith retired now, claims a friend of his loaned a 6mm/284 out for load development by a major manufacturer. Shot 3/4 inch groups. Developers shot it much and it is alot of powder in a small hole. Came back with the rifling "rounded" up the barrel 1/2 way or more... More than just "throat erosion." He thought "rebarrel." But he shot it first. Still grouped 15/16s so he put it back in the rack...

You have to set your own standards. If you are going to shoot competion, I have heard of center fire competitors that replace barrels every year (or 2) on "general principles." And not with a "factory take off" cheapie barrel... And the match .308 loads are not "hot, hot, hot" that I have seen recommended. (Some of these barrels are cut down and re- installed on deer rifles...) If you want "deer accuracy", say 12 inches or less out to 350 yards, doubt you can wear out a .243 with factory loads (unless you are stinking rich...) Now you go play in a p'dog town with one rifle and lots of ammo and --yes, I know how you swear/ promise to "pace yourself" HA, HA, HA-- you can "ruin" a barrel in a day, maybe a half day (so take 3 or 4 guns...AND ROTATE THEM! Or barrels for a TC system, like that.) 

When you listen to all this and "sort it" THEN it starts to make sense. The old woodsman with a .30/30 that he has shot "a million times" (with factory ammo) and it still "shoots good, goes bang!" His gun will outlast him because he does not expect too much and it can continue to deliver to his standards. Then there is the competitor who is complaining about fouling after 5 or 6 or 10 shots... "No good barrel", when it might need break in, it might be a bad piece of steel--that does happen, but it was only marginally satisfactory from the start whatever it cost. I am nearer the woodsman (drug store type) looking up. I have standards, but to get something to shoot at p'dogs... welllllll... Where will you be?

Jack O'Connor once observed that, in his day decades ago, it took about $1,000 worth of ammo, reloads even, to "shoot out" a factory barrel and only $100-$200 to replace that barrel with a high quality pipe. So if you got the $1,000 to wear it out, how hard will it be to spend another $100 or so to start over. Inflation has increased the numbers, but the ratios still hold, pretty much. luck

[shepherm]

Jack O'Connor once observed that, in his day decades ago, it took about $1,000 worth of ammo, reloads even, to "shoot out" a factory barrel and only $100-$200 to replace that barrel with a high quality pipe. So if you got the $1,000 to wear it out, how hard will it be to spend another $100 or so to start over. Inflation has increased the numbers, but the ratios still hold, pretty much. luck

This is a very point.

[JerryNH]

So based on the NRA article, is it safe to say a magnum barrel will not last as long as lower pressure rifles?

[gunnut69]

All else being equal that would be a true statement..

[GaryCrow]

If you manage to shoot out the barrel on a .243 then you should congratulate yourself and celebrate by buying yourself a new barrel.  I don't think the slow burning powders really help increase barrel life.  What degrades barrel life the most is shooting the rifle with the barrel hot.  As a rule, if the barrel is too hot for you to grab and hold with your hand then you should let it cool some before shooting again.  A barrel will heat up a lot quicker in the hot summer sun than in the depths of winter so plan accordingly especially if you're intending on some quick fire varmit shoots.  Once that barrel steel is hot then it's much more prone to throat erosion than if it's cool.  Keep it cool and it'll last a long time. 

[gunnut69]

Powder types have a profound effect on barrel life. The m16's use of ball powder with its deterant coating is one of the reasons for most of it's early problems. The powder was used because tests indicated longer barrel life with slower burning powder.. The problem with magnums isn't the burn rate of their powders but the quantity of powder used.  In most dogtown shoots you'll find a lot more 223s and 204s than 243s or 22-250s. They allow higher rates of fire before they overheat.. Also I am really inerested in the tests run by Norma. Where did you see this info.. I am interested in what pressures were used to drive bullets to the velocities generated by the 50-60,000 PSI generated in a high intensity rifle round..

[car hauler]

Has anybody worked with any barrel cooling devices, etc? In a prairie dog town etc. I have a co2 bottle made up that I let go down the barrel. But it didn't work out to well as it took a lot of gas to cool down. 30-cal. barrel.

[gunnut69]

I have seen varnit rigs that used water to cool the barrels.. Don't remember the exact method but the whole rig was a little 'out there' for my tastes. It was self leveling and have a canopy. Built in benches and coolers.. It was sort of a gun boat on wheels.. The simplest way to control heat is th use multiple guns and calibers that don't generate a lot of heat. The 222/223 are good calibers with maybe a 22 rimfire for the closer shots and a Hornet for a bit further out. A close friend used to do several hunts a year with his budy and their kids. The would use a long weekend and he carried 3 223's as primaries. 22 rimfires and Hornets and his current deer rifle rounded things out. He once told me that you learn more about long range shooting and shooting in general in a long weekend in a dog town than in a lifetime of deer hunting. He was using a 300 mag in a No.1 for deer at the time and he managed some extremely long kills on PDogs with it.. He would use a 223 until the barrel heated than switch to the next. By the time he'd worked his way thru the third one the first was nearly cool enough to shoot.