How can you tell if a cartridge design is a barrel-burner, just from reading specs?

[Dannix]

How can you tell if a cartridge design is a barrel burner, just from reading its specs? Case capacity / caliber, or something? I'd liked to be armed with the knowledge while reading up on all the great wildcats out there.

[2ndAmendmentNut]

That’s a good question. Not sure but it seems like to me the calibers that have excessive case capacity compared to the weight of the bullets they are pushing are the barrel burners. For example I met a guy at the range that had a 22-06, yup that is right a 30-06 necked down to 22. He was getting some crazy velocity from that gun, also said that he had worn out one barrel already in about a 1000 rounds! Perhaps velocity is the biggest issue? Also allowing the barrel to get excessively hot is not too good for the barrel either. Oh and the term “barrel burner” seems to be what an old fart will call anything under 30cal with velocity greater that 3000fps.

[2ndAmendmentNut]

Also keep in mind that the supposed "barrel burners" of past decades are not really barrel burners today with today’s modern steel and modern powders. The 220 Swift comes to mind here…

[Dannix]

Well I read the 6.5x285 (http://www.6mmbr.com/SixFive284.html), for example, gets to around 1k at which point the barrel loses accuracy. This is ~3000fps.

Maybe it's an issue of case body diameter / bullet diameter?

There seems to be more to it than simply fps.

[white eagle]

alot of barrel burners are way over bore cartridges like the 22-06
a big case with a relatively small bullet
I have heard of some not even making the 1000 round count

[Dannix]

Maybe the issue is case body diameter to caliber and there's some sort of maximum ratio? Necking the .308 down .62mm to 7mm for the 7mm-308 doesn't seem to create barrel life issues, but necking the .284 .5mm down to 6.5mm for the 6.5x284 drops barrel life by a whopping ~67%. 7mm-300 WSM apparently yields only ~500 of accurate barrel life!


Edit: Ok, these figures are very rough (e.g. I'm using inches for case, mm for caliber), but here's a simple comparison of case diameter and caliber:


Caliber Base Diameter Caliber BaseDia/Cal Cal/BaseDia
.284 .501 in 7mm 0.07157 13.97206
6.5mm-284 .501 in 6.5mm 0.07708 12.97405
.308 .4709 in 7.62mm 0.06180 16.18178
7mm-300 WSM .555 in 7mm 0.07929 12.61261

Well, from this small sample, there does appear to be a correlation. Based on this thought though a .416 belted magnum would have even higher barrel life than a .308, which surely can't be true.

[Piedmont]

It is determined by pressure combined with the amount of powder burned. At the high end of both you will get fast throat wear.

It isn't just the amount of powder burned, though. Ken Howell designed a series of cartridges that had larger than standard capacities that he then chose to run at less than full pressures. This gave him both high velocities and longer barrel life.

[Dannix]

It is determined by pressure combined with the amount of powder burned.
Aren't these values basically the same between the .284 and 6.5mm-284 though?

[Dannix]

There's a good general overview here, specifically Octopus's post:
barrel life (http://www.accurateshooter.com/forum/index.php/topic,3737650.0.html)
The post doesn't address where tipping points occur though, just general rules.

[PAT303]

It also depends how fast you shoot,more rounds means more heat. Pat

[Dannix]

Indeed. I'm talking cartridge design only though, cerebus paribus (ignoring use, like rapid fire / heat).


Aspects that would need to be represented in a formula for a numerical comparison (I think I got them all):


Ratio of Case Shoulder diameter to caliber diameter
Powder weight
Powder volume
Powder burn rate
Pressure
Velocity
Bullet weight -- as per Octopus. This one I don't understand. I'll have to re-read Octopus's post to see if he elaborates on this.


The real issue I imagine with coming up with a formula is getting the right ratios down. For example, varying the powder charge may cause a linear influence on barrel wear, but pressure or "Ratio of Case Shoulder diameter to caliber diameter" may be a geometric influence.

My brain's tired and it's past my bed time. Please forgive any typos. I'll crack out some spreadsheet action tomorrow.

[Piedmont]

Aren't these values basically the same between the .284 and 6.5mm-284 though?

On the surface, yes. But in reality no, because the 6.5 is burning much more powder for the bore size, so the barrel life won't be as long.

[Bret4207]

Several years back The Accurate Rifle/Precision Shooting had an article that explored neck angle in relation to throat erosion. The idea was any case that had a neck angle and a neck/case mouth relationship that would allow the hot gases to be directed at the throat area was determined to be worse in that respect than something like a 30-'06.

[Rocky Raab]

Years ago, I did some serious load book crawling and calculator tapping and came up with this:

The point at which a cartridge becomes "over bore" is when the case capacity (in grains of water) exceeds bore diameter squared, times 1000.

For example: .22-caliber guns have a .220" bore. 0.220 squared is 0.0484. Multiply by 1000 and max case capacity is 48.4 grains of water.

Note that rounds like the .22-250 and .220 Swift are just barely under that limit, while known "barrel burners" like the .22-243 are just above it.

Doing the math for other popular bore diameters gives us these limits:

.24/6mm -- 57.6 grains of water
.25 -- 62.5
.27 -- 72.9
.28/7mm -- 78.4
.30 -- 90

[Lloyd Smale]

that is basicaly the trick to the whole deal. Ive got a 257 weatherby that i dont even know how many rounds have been through. I keep it clean and dont shoot more then a slow 3 shot group with it and never have had the barrel to hot to touch. Ive had this gun for over 25 years and ive shot many many rounds through it hunting and for load developement and it shoots as well today as it did the first day i brought it home. Another thing i tend to do is not use ball powders in overbore guns. They burn hotter and cause more wear. In even a seriously used hunting rifle burning out a barrel isnt going to happen if you take a few small steps to avoid it. Now in a varmit rifle that gets shot till hot and put away wet it may be a consern but even when varmiting ive allways took at least 3 guns so i can rotate to keep them from getting hot and take along a cleaning kit and try to at least run a bore snake through them ever 10 rounds or so.
There's a good general overview here, specifically Octopus's post:
barrel life (http://www.accurateshooter.com/forum/index.php/topic,3737650.0.html)
The post doesn't address where tipping points occur though, just general rules.

[mike in co]

Well I read the 6.5x285 (http://www.6mmbr.com/SixFive284.html), for example, gets to around 1k at which point the barrel loses accuracy. This is ~3000fps.

Maybe it's an issue of case body diameter / bullet diameter?

There seems to be more to it than simply fps.

the 6.5x284 is built as a target gun...pushing bullets hard for small groups at high velocity.....and yes some only get 1000-1200 rds but in the name of accuracy at long distance...600-1000 yds.

[mike in co]

On the surface, yes. But in reality no, because the 6.5 is burning much more powder for the bore size, so the barrel life won't be as long.

or no......
there are two very distinct 284's. the original and the long throated benchrest version.
the br version bbl i sprobably just a little longer than the 6.5x284.
they shoot a 180 at 2600 plus fps........in little bitty groups

mike in co

[Larry Gibson]

Assuming we're talking high end bottle necked cartridges, the easiest and perhaps best method of comparison is the simple exansion ratio. However, several things must be assumed to make any comparison valid; primarily barrel effective lengths (base of bullet or case neck to muzzle) must be close to equal and the MAP (Maximum Average Pressure) levels must be close. The expansion ratio is determined by comparing the volume of the bore to the volume of the case. An expansion ration of 9:1 means the bore is nine times the volume of the case. The lower the expansion ratio heat and erosion has a greater effect on the bore, particularly the throat and first few inches of the bore. A simple comparison to make is with the 25-06, 270 Win, 30-06 and 35 Whelen all with 24" barrels and an assumed MAP of 62,000 psi. If you do the math you will quickly see that the 25-06 has the lowest expansion ration and should there fore give the shortest barrel life. That is indeed the case (pun intended;-) ).

Larry Gibson

[jameslovesjammie]

When you are talking a BR cartridge like the 6.5-284 on a benchrest/long range forum like 6mmbr.com and they say a barrel is worn out in 1,000 rounds, they are talking about competition grade accuracy, not hunting/plinking/general shooting accuracy. You may open up to a cloverleaf pattern instead of one ragged hole. Those guys over there are CRAZY accurate and extremely anal and meticulous about their equipment.

[stephen perry]

I don't think you can know how a barrel and a cartridge are going to match up from the get go. My example is my Rem 742 with ball ammo. Now ball ammo a few at a time ain't no big deal but I shot 500 in a half day Desert blast many times during the Summer in Lucerne Valley thermometers are an otion most don't bother with out there hot is hot, hotter than Nebraska. The best we ever did was run a couple patches of Hoppes at the end of the day.

Now this gun being a semi-auto I never ran a brush, having no bore guide for the muzzle. My dad would drain the gun with acetone a couple times a year and I would keep on shootin. What you might call a burned barrel I knew not when I was 13. My gun was a genuine barn burner wouldn't want to play war games with me if all you had was a springfield or a garrand I would match you shot for shot and was a better shot, I had 3 extra loaded clips.

Later loaded Cast in the gun. A gun that should have been blown out from years and cans of ball in Desert shooting. I had a Weaver 4x scope and proceeded to blast the Range targets not the sticks. I don't lie about group targets. I was shooting about 1 1/2-1 3/4 inch groups, an occasional 1 inch and some 2 inch. Was the barrel burned probably the gun wasn't made as a throw away gun. One of the best barn burners Remington ever produced in a Civilian gun.

Stephen Perry
Angeles BR

[Rocky Raab]

Larry, the barrel length issue is the main reason I used a system other than expansion ratio. My formula is based on case capacity versus bore diameter only, and seems to track quite well.

[izzyjoe]

i ain't knockin' you stephen, but i had a 742 and i was not impressed. i sold it to a friend he has killed a truck load of deer with it. so go figure. i now own a bar, and i think it's better built. but just an opinion. :)