Bolt action overheat

[madhat]

is it possible to overheat a bolt action rifle? i usually spend 20 seconds maybe 40 between shots, is that enough?

Browning A-bolt II Stainless Steel

[Scorch]

Of course it's possible. But the rifle will tell you when it's too hot, you won't be able to touch the barrel.

[madhat]

so blowing 10 rounds in 60 seconds could warp the barrel? i say 10 because i did before an woo was it hot, i wish i had a laser thermo to temp it

[tobnpr]

No, ten rounds in one minute won't warp the barrel.

Once. How many minutes you could continue, who knows. Perhaps indefinitely, depends on the weapon, the barrel and the caliber I suppose.

The M4 has a sustained rate of fire (indefinite) of at least a dozen rounds a minute, or so I've read...

But why run a bolt action so quickly?

Any rifle barrel- including a bull contour- will heat up and probably begin stringing shots after a short period of that frequency.

[kraigwy]

Lot of people over think or worry too much about barrel heat.

According to Hatcher's Book of the Garand, it takes very little shooting for the M1 to raise temps to 500 degrees.

You'll get a lot hotter then that shooting the Infantry Trophy Match (where you fire as many as you can in 50 seconds, then move to another yard line and do it all over again. You do that at 600, 500, 300 and 200 yards>

Suckers get hot.

I measured the chamber of my Model 70, it went from 85 degrees before firing to 104 degrees with 5 rounds in no time at all.

Sounds bad, but it can't be helped. Any metal is gonna get hot when you add that much heat, energy and friction.

But it doesn't really hurt anything as long as the barrel doesn't make contact anything to disrupt the harmonics.

A barrel when fired is like a water hose, Un confined it wobbles all over the place in a constant patterned. No if you interject something to hit the water hose you're going to change the flow.

I've played with getting barrels as hot as I could, and different heat of ammo, like laying ammo in the sun vs. laying it in the shade.

Ammo is much more critical then the temp of the barrel.


I've shot M16 barrels and M-60 barrels until they got red hot. Once cooled they can shoot again.

Of course, heat will decrease barrel life.

[madhat]

this is my first serious gun for hunting longer ranges hence 30.06 caliber, i'm just worried about ruining the browning i just bought lol don't want to be out 700$ haha and when i look down my barrel there is a bit of built up copper streaks, when should i be concerned and cleaned those out? i don't want to cause a obstruction

[PawPaw]

Originally Posted by kraigwy

I've shot M16 barrels and M-60 barrels until they got red hot. Once cooled they can shoot again.

I've had run-away's on an M60. There's a reason that they include an asbestos glove in the spare barrel set. Red-hot barrels tend to decrease barrel life.

[kraigwy]

when i look down my barrel there is a bit of built up copper streaks, when should i be concerned and cleaned those out?

NO,

You'll ruin a rifle more by over cleaning or improper cleaning then you would shooting.

My M1 was made in in '42, don't know how much its been shot before I got it. I got it from CMP (then DCM) in the early 80s and shot the crap out of it. I'd take it to my sniper schools (we used the M1C/Ds) and shot it until sap boiled out of the stock. It still shoots today.

Just shoot it and enjoy it, rifles last a lot longer then people think.

[Groundhog34]

IMO it is very easy to get a barrel overheated. I find after shooting 5 or 6 rounds in a couple of minutes the barrel bets very hot. It affects accuracy greatly, groups spread out 6 or 8 inches. Does it cause permanent damage probably not but it is impossible to sight in a hot barrel.

[kraigwy]

I find after shooting 5 or 6 rounds in a couple of minutes the barrel bets very hot. It affects accuracy greatly, groups spread out 6 or 8 inches.

How do you explain target rifles holding their zeros in rapid fire.

Lets say 10 rounds in 60 seconds (with a mag change) and still holding MOA or better.

Or worse, Firing as many rounds as you can get off in 50 second in a Rattle Battle, then doing it again 3 more times. They still shoot.

If your rifle expands 6 or 8 inches in 5 or 6 rounds you have lots of problems and heat isn't one of them.

[coyota1]

I had a new england single shot break open 223 that temporarily warped. The groups would string about 6" at 100 yards after it warmed up. I sent it back to the factory 3 times before I unloaded it.

[impalacustom]

I'm thinking this guy doesn't have accuracy problems with rapid firing a bolt action. Notice he fires multiple shots in rapid succession. http://www.youtube.com/watch?v=byChk...layer_embedded

[Tikirocker]

Definitely possible in war ... during WW1, Australian soldiers came under a charged attack at Gallipoli from the Turks. The Aussie soldiers were firing non stop from their trench and I have read accounts of one Aussie stating that he managed to overheat and seize two Enfields during that battle, due to the high rate of continuous fire. When the rifle seized another soldier would hand a cool one up from cover and they would continue ... the Turks got massacred that day.

Most people are not going to experience anything like this in either normal target shooting or hunting.

Tiki.

[hooligan1]

At the range I fire five to ten shots through my rifles pretty quick, and they get hot and luckily they don't string groups, they continue to put them into good groups, and those barrels get hot hot.... I just pick up another one or watch someone else fire some rounds.

[Bart B.]

Kraig's made some good comments about barrels overheating and not changing point of impact. Here's supporting comments.

Lake City Army Ammo Plant tests rifle ammo shooting 200 to 300 shot groups at 600 yards. With a good batch of 7.62 NATO match ammo, they'll all go inside 6.5 inches. All shots are fired when the wind's calm and about 10 to 15 seconds apart.

Those Infantry Trophy (Rattle-Battle) matches Kraig mentioned; each rifleman on a team typically did the following with his Garand (and later with M14's and M16's)

At each range of 600 and 500 yards prone then 300 yards sitting, getting into position and aiming at where the targets will come up then taking two deep breaths when the range officer commands "Load and be ready" and loads a full clip. When he sees his target start up over the safety berm he shoots 8 rounds at it, reloads, shoots 8 more then reloads and shoots the last full clip of 8 watching the silhouette target start down a second after his last round's fired. All 24 rounds in 50 seconds. That's under 2 seconds between shots with reloading and going back into position and taking two deep breaths taking about 3 to 4 seconds twice. Any left over ammo's divvied up among the 6-man team where they move to 200 yards and shoot standing. You get 4 points per hit on the silhouette at 600, 3 at 500, 2 at 300 and 1 at 200. If all targets having more than six hits, you get extra points. There's 8 targets; usually two shooters splits their rounds between two targets; they're called a "swing man"

There's been more than a few 2nd degree burns on bare necks from super hot barrels touching them while being mishandled after firing a string. And good Rattle-Battle rifleman can put all their shots inside 12 inches at 600 yards, 10 at 500 and 8 at 300 and 200. They use their regular match grade barrels. And that doesn't cause any more wear than regular rapid matches shooting 10 shots in 60 or 70 seconds.

If you barrel shoots bullet to some other point of impact as it heats up, there's three main causes and one that's not part of the hardware. . . .

The barrel's not stress relieved properly; often is the case with cheap aftermarket barrels.

The receiver face wasn't squared up when the barrel was fitted; the high point puts a stress line down the barrel at that point when the barrel heats up expanding and bending on that stress line axis.

The barrel expanding over an epoxy bedding pad under the chamber puts vertical stress on it; the vertical barrel whip when fired gets different and bullets don't leave the same tiny range of angles they would normally do.

And sometimes the shooter doesn't keep the same exact position shot after shot after shot. . . . .

[mr.t7024]

No... Cliff

[Bart B.]

tobnpr claims:

Any rifle barrel- including a bull contour- will heat up and probably begin stringing shots after a short period of that frequency.

Tell that to my friend who put 40 shots 15 to 20 seconds apart into a 1.925" group at 600 yards.

I've put 30 shots fired that fast from a long, heavy bull contoured 30 caliber magnum barrel into less than 5 inches at 1000.

And long range benchresters often shoot 10 shots five to seven seconds apart during a lull in the wind and get excellent accuracy sometimes winning matches and setting records doing it.

[tobnpr]

OK, so if ten rounds per minute won't affect accuracy in a bull contour, are they immune to stringing? Or what would it take?

Also, not related...
But since heat is the enemy, wouldn't this accelerate throat erosion?

[Bart B.]

tobnpr, a skinny sporter barrel won't string shots as it heats up either. Lenght and thickness doesn't matter. The only thing that does is how the barrel's stress relieved, how external forces on it change as it heats up. The amount such barrels heat up isn't enough to change their metalurgy such that their stiffness or rigidity changes significantly. While a stainless steel rifle barrel diameter will increase as it heats up, it won't be more than .001, if that much, for a 100 degrees F increase in temperature.

Best example are the military service rifle barrels mentioned earlier that don't string shots as they heat up. Especially those used in matches when 24 shots are fired in twice as many seconds. They have about the same contours as standard weight sporter rifle barrels.

I've searched the web for any engineering formulas used to calculate steel pipe stiffness or rigidity that have inputs for how hot or cold the steel is. None I've found have them. Evidence to me that heat doesn't change how a rifle barrel vibrates or whips going from cold to hot. If it starts stringing, some external force is changing how it whips and vibrates such that bullet leave the muzzle when its axis points somewhere else as the bullet leaves compared to when it was cold.

There is one thing that will cause shots to go high from a hot barrel that may not have been mentioned; barrel heat transferring to the powder. As powder gets hotter, it burns faster and shoots bullets out faster. They strike the target higher due to flatter trajectory form their higher muzzle velocity. So, don't leave a round in a hot chamber for more than about 15 seconds unless you know how much elevation correction on the sights will make it strike where previous shots were fired from rounds with cooler powder in them. I've shot long range matches having to wait for over a minute with a round in the hot chamber for that time. I come down 1/4 moa for every 30 seconds a 30 caliber magnum round "cooked" in a hot chamber and they struck where they were called. Then come back up on the sights to normal zero for the range and continued shooting; never any vertical change in bullet impact on the target.

[Mobuck]

I watched a shooter trying to sight in a new 30/06 at a range I visited in Colorado 2 years ago. His elcheapo(but cool looking) scope was not adjusting and he just kept blasting away. After he'd used up most of his 60 rounds of ammo, I offered some advice and suggested he let the barrel cool a little. The guy foolishly laid two fingers on the barrel just in front of the chamber and immediately received two fine blisters on those finger tips.
I can't see why one needs to shoot that quickly unless in combat but some do. I've seen the borescope results of overheated barrels and the snakeskin looking interior is not what I want in my bore. Anyone shooting my rifles at targets had better count to ten nice and slow between shots or lose his privileges.

[Shotgun693]

There's not much of a reason that I can think of to shoot a bolt action hunting rifle that fast, that much. Military rifles are different. It's like saying that because I can drive my Vet a hundred miles an hour from Houston to San Antonio then there's no reason I couldn't do the same with a Ice Cream Truck. I've fired a G3 until I couldn't hold the forearm, the gun was designed and built for it. When I really hunted a lot I might have fired 5 to 6 rounds a Deer Season, I'm sure I never got the barrel on a deer rifle so hot I couldn't have put my bare finger against the barrel.

[tobnpr]

tobnpr, a skinny sporter barrel won't string shots as it heats up either. Lenght and thickness doesn't matter. The only thing that does is how the barrel's stress relieved, how external forces on it change as it heats up.

I guess this is akin to barrel cleaning, where there are many opinions.
Dan Lilja thinks differently (and like I said, his is only one opinion, but one that I respect)...

He does believe that rigidity- obviously a function of length and thickness, does matter:

In another article on barrel stiffness, we outlined the mechanics and math behind barrel rigidity. The simplified version of that article is that a barrel too long for its diameter is not rigid. It can be whippy and accuracy will not be at its best. Generally speaking, a short and fat barrel is more accurate.

And while I agree that there is more "to" the "skinny barrels heat up and string shots" generalization, I still believe that due to the fact that they are less rigid, any residual stress in the steel will become more evident as the barrel heats up- and strings shots- due to the simple reason that they are less rigid.

I do believe that this would be less evident, in a "skinny" (factory) contour barrel that is of high quality, likely cut rifled and made from stress-relieved steel.

But the stereotype persists- and like most- has some merit- because most light contour barrels are mass produced, not stress-relieved and of high quality, and will be more likely to string shots when hot.

[ndking1126]

most light contour barrels are mass produced, not stress-relieved and of high quality, and will be more likely to string shots when hot.

I'm glad I caught this post. I thought it was pretty much accepted fact that barrels tend to change point of impact when they got hot, whether stringing or just opening up. When I lived in the South, I just quit going shooting if the temp was above about 90, 95 degrees because like clock work, after 4 or 5 shots my Rem 700 ADL in .30-06 groups started opening up. I typically waited 3 minutes between shots with bolt open. I also noticed that it was about this time that the barrel was too hot to touch.

My barrel is free floated, but action not bedded. I loaded bullets one at time directly to the chamber and kept the rest of them grouped in the same temperature (usually in the shade) and the time in chamber between loading and firing was consistent.

Now in the winter, with an ambient temp of more like 30-40 degrees, if I waited 3 minutes between shots, I never noticed the group opening up (unless it was me of course..). For those of you who say that temps don't open up groups, can you offer any explanations as to why I got the results I did?

But to the OP, if its possible to overheat your rifle, you were no where near it. You would have to do something ridiculously absurd (like fight off the Turkish Army.. great story tiki!) to get there.

[Bart B.]

Here's two barrels fit to receivers bolted in a stock; both 30 caliber. The bore diameter of .306 inch was used to equal what a typical 4-groove area of .308" groove diameter would be (.0736 square inch). My software only uses one diameter for the bore. Use the profile below for dimensions listed:



First barrel, typical 24" sporter rifle:

bore diameter = 0.306 inch
breech diameter A = 1.25 inch
reinforce large diameter B = 1.25 inch
reinforce small diameter C = 0.8 inch
muzzle diameter D = 0.6 inch
reinforce length AB = 2.75 inch
reinforce taper length BC = 3.25 inch
main taper length CD = 18 inch
total length = 24 inches
total weight = 3.191 lb

Second barrel, typical 30" Palma rifle:
bore diameter = 0.306 inch
breech diameter A = 1.25 inch
reinforce large diameter B = 1.25 inch
reinforce small diameter C = 0.92 inch
muzzle diameter D = 0.82 inch
reinforce length AB = 2.5 inch
reinforce taper length BC = 2.5 inch
main taper length CD = 25 inch
total length = 30 inches
total weight = 5.095 lb

Which one's stiffer and by how much?

One of them vibrates at about 71.5 cycles per second and that's about the frequency where the greatest amount of bore axis angular spread happens at the muzzle as it whips in the vertical axis for that barrel's contour. It goes through one cycle in about 14 milliseconds. Bullets take about 3 milliseconds to go from case mouth to out the muzzle.

[madhat]

interesting data bart thanks for the share!