[Prairie Buck]

How hot is a hot barrel? At what point do you set your gun aside to let it cool down? Besides the changes in accuracy associated with barrel temperature, what other concerns are there with shooting a hot barrel? I have a .30-06 Husquavarna from the late '50's that shots best when hot. You can hold your hand on the barrel but not for long. I have never had any education on this topic. Nor have I seen any discussion of it on any of the board.

 

[MikeG]

It's subjective, of course, which is why you never see anyone post something like "your barrel will cook the throats at exactly 155.2345 degrees, and be just fine for any amount of shooting below that....."

I don't believe that there is a temperature point where the steel suddenly is more prone to be shot out. If it barrel is hotter - it will wear out sooner, and vice-versa.

Then you have different steels available for barrels, each one has it's own unique wear characteristics.

On a target rifle, this is a pretty valid concern (group size whether hot or cold) but on a hunting rifle, the overriding concern should be "can I count on the first shot from a cold barrel going exactly where I want it?" After first shot, most game doesn't hang around long.

On your gun, a guess is that the barrel moves in the bedding a little when it heats up. Whether the barrel is crooked or has some stress points from the manufacturing process, it's hard to say.

I would personally start by free-floating the barrel in the stock, shoot some groups, then add pressure between the forend of the stock and the barrel. You might find a combination where it will shoot better cold tht way.

 

[Prairie Buck]

Subjectives

Thanks for the response MikeG. Have been working on the floating. It this point still reducing foreend pressure. I use all of my guns for both target and hunting. Both hot and cold barrels. The Husky is the only one that has given major PA to PI changes with temp changes. I at least have an idea what the others do as barrel temp changes. The Husky is all over the map, but is improving as the forearm pressure comes down. Living on a boat in BC with the hunidity changes does not help.

I am still interested in the subjectives on when to switch rifles due to barrel temperature while at the range.

 

[kdub]

Barrel heat is a major consideration where I live. In the winter, early spring and late fall months, the rifle is generally set aside after 3 rounds have been shot within a 3 minute time period. The barrels are warm to the touch, but not uncomfortable to hold. In the late spring, summer and early fall periods, I take a 12-pac cooler that contains frozen bath towels. When the requisite 3 rounds have been fired, the barrel is wrapped or draped with a towel and set aside until cool. Due to extreme low humidity and ambient heat there is no concern of rusting the barrels! The towels are used in this fashion until they are no longer cool, then draped around my neck to help cool me down. When I get home the towels are re-wetted, wrung mostly dry, placed in foil wrap or baggies and shoved back into the freezer for the next trip.

Most of my rifles are used for hunting, therefore, I'm trying to duplicate that "cold barrel 1st shot" syndrome - also, for the best 5 shot grouping to verify load componets and velocities.

 

[MikeG]

I've got the same problem in Texas, shooting during the summer.

I take 5 or 6 guns the range, shoot one group, go get a different rifle, shoot one group with it, etc.

Go through them all then get out the .22 and shoot it a while, start back up again.

Barrels never get much cooler than 'warm'.

 

[Gunnut45/454]

Mike G
So you wouldn't through more than 5 Rounds through a barrel before letting it cool down? I have also wondered about this. Besides the obvious group change on paper- has there been any Manufactors testing done to show or guage the effects of multiple shots in a hot barrel?

 

[MikeG]

I typically shoot 3-shot groups for testing hunting loads. I do not do any target or benchrest competition. Three shots gives a pretty good idea of practical hunting accuracy, and three shots generally gives you a good idea of whether or not you need to change your scope settings. If you can get your groups down to MOA for 3 shots then you can have some confidence in them as far as repeatability and scope settings.

For a lot of shooters, myself included, I believe that it's hard enough to really concentrate on sight picture, scope/parallax control, breath control, trigger, consistently holding the gun on the bench, etc., for 3 shots and with 5 I'll almost certainly let one off when I wasn't ready. If I feel that I threw one shot out of the group, then I may fire one more.

If you don't think that the number of shots in a group matters, get an accurate .22 rimfire - a true "one holer", and work on shooting long strings (say 10 shots) and that will tell you a world about your ability as a shooter to really concentrate for 3 shots vs. 5 shots or more. Hey, if you can do it with long shot strings, great!

Plus - it does save bullets. The last several times I have worked up handloads, one time it took 10 bullets to get an acceptable handload and scope setting for a .458 Win Mag - and you don't shoot that gun from the bench more than you have to! And another time it was 12 bullets. Of course some of this is luck, but if I have to shoot 10 groups, then that's 30 bullets vs. 50 bullets and I have 20 bullets left in the box to shoot pigs, deer, etc.

Of course you occasionally have to chase bedding or scope problems, I ran probably 120 or more rounds through my .35 Rem till I got it sorted out. Fortunately, factory ammo is cheap for that round.

It does depend on your gun - a .35 Rem at 33,000CUP doesn't heat up a barrel like a .22-250 at 50,000CUP, as you might expect.

As I understand it, when the steel gets heated to a certain point, it loses carbon and/or temper, then softens and gets washed away by the bullets/powder gasses.

You can think of it as spot-annealing, in a microscopic scale, if that makes sense. A little spot on the lands of a rifle or in the throat is going to absorb a LOT of heat real quickly, then dissapate it to the surrounding steel. But dissapating heat takes time, it isn't instantaneous.

I'm sure the manufacturers don't publish any sort of information on this, there are too many differences in individual barrels. They all aren't going to be the same hardness, they certainly won't all have the same surface finish (and friction with the bullet does contribute a lot of heat), then you get into differences in powder types (ball vs. stick, single-base vs. double-base), and how dilligent each person is about keeping the barrel clean. Same reason most manufacturers don't publish accuracy guarantees, either.

Don't let the thought of washing a barrel out discourage you from practicing, though - use either lighter loads (reduced loads with cast bullets and barrels last a long time) or break out the .22.

 

[kdub]

Good discourse, MikeG -

Only thing I can add is hot loads generate a lot of heat, heavy bullets have lots of friction and thick barrels are longer to show the effects of heat than thin, whippy barrels.

There are powder brands now advertised as "cooler burning", which means the graphite coating is heavier to retard the burning rate, hence less peaking pressure and less velocity.

Something will be sacrificed the hotter the loads and the warmer the steel becomes. Also, higher ambient temps will cause the ammo to develop higher pressures. Never had a round cook off in a hot chamber, even while in the military service, but I still remember changing barrels out on hot .30 cal Browning air cooled machine guns (not pleasant) and having to re-headspace them so they would function properly. Often wondered what the throat looked like in those barrels!

 

[kciH]

A lot of good advice here. I'll add that the rule I've used for "when to say when" on barrel heat is when you cannot hold the barrel for 15 seconds and not burn your hand. This, I would judge, is the hottest you should get your barrel in a non-combat situation. My .340, with a wispy barrel, will easily get this hot after 3 spaced shots. Less overbore cartridges will not approach this heat level until many more shots have been fired. An example is a bull barrel I have for my Contender Carbine in 6.5x30 (30-30 necked down) It will fire 10 deliberate shots without heating the barrel beyond warm, into under 1 moa with no discernable shift in the group within the string. There is no real answer to the number of shots because of different cartridge/load/rifle(pistol) combinations.

The area of rifles shooting to different point of aim after heating up is one I have had fits with in the above mentioned .340 and a few others, especially with light hunting weight barrels. You really have to play with the rifle's bedding and barrel channel to optimize performance under the conditions you lay out. Some barrels will make you want to pull your hair out, no matter the bedding/barrel channel scenarios you try. I believe this is where you have to make the decision to try cryo-treatment or have a new barrel screwed on. As always, you should make sure your ammunition is as consistent as possible, including bullet runout, before having a new barrel installed. One good tip I can offer in the area of bedding is to use a hand laid synthetic stock if it's in the budget. The injection molded stocks that come with most synthetic stocked rifles are crap. I have a early Model 70 Winlite with the factory MacMillan stock that shoots better than any other factory rifle I own, no matter the humidity, heat, etc, this includes rifles with heavy barrels in place of the wispy "featherweight" Winchester barrel. The .340 went from being a factory Weatherby synthetic, with every bedding trick in the book tried, to a hand laid, strong synthetic. It also went from about Weatherby's 1 1/2" gaurantee, to a little over 1/2 moa groups with the exact same loads and barrel. The factory injection molded stocks may be fine in some calibers, but the heavy hitters seem to perform poorly with them. I know that some people have had excellent groups with the "cheap" stocks, but one group does not make a consistent rifle.

 

[J Miller]

How hot is a hot barrel? At what point do you set your gun aside to let it cool down?

Well, how about hot enough to melt a fiberglass / polymer clamp on bi-pod?

A friend of mine had a Mini 14 and we were out in the AZ desert banging away at target when we smelled something like melting plastic. We stopped shooting and noticed smoke coming from the front of the rifle. The barrel had gotten so hot that it had melted the bi pod. What a mess.
We wern't even shooting rapidly. Just slow and consistant.
I figure that is about time to let it cool down.

 

[loader]

I give my rifles a rest when the bbl, just ahead of the chamber,will melt parafin. If you open the breech and stand the rile up, the heat will have a chimney effect and cool much faster.

A big accuracy concern is how hot the chamber makes a round in battery before you tough it off. This increases pressue and velocity, changing the vibration characteristics of your barrel.

 

[Kosraedan]

I am somewhat new to target shooting, but I am not sure the concern about barrel heating may not be overstated. There is actually a temperature at which the carbon steel barrel molecular structure begins to be altered by heat. Carbon steel is annealed at between 1300 and 1500 degrees F or so. That is, the steel will lose its "temper" and become softer.

It would seem that this would be where concern for wear would begin. Otherwise, the barrel actually expands with heat. The bullet will touch less metal. Thus barrel friction is reduced, not increased, with heat. One would anticipate that barrel wear or barrel damage would be reduced with a "hot" barrel. Obviously, I am speaking of normal heating that occurs from firing the gun.

While it is frequently stated that "heat is the enemy of a barrel" I have noticed no explanation for that statement. Sometimes "general knowledge" is nothing more than oft repeated truisms. I don't mean to be critical, and my reasoning may be flawed, but if so, I would appreciate someone showing my error.

Of course, heating can cause temporary distortion if the heating is not uniform or if the barrel is not uniform. However if that is a source of barrel wear it should be localized, typically at the point of maximum deflection that should be past mid length of the barrel.

Any inaccuracy is far more likely to be the result of powder heating from a hot chamber. Tests have shown that a 50 degree rise can increase chamber pressure by as much as 10%, secondary pressure that can be seen due to barrel expansion, or the fact that barrel harmonic nodes shift as the barrel expands such that any particular load no longer is optimized for the barrel.

I certainly agree that a hot barrel may not shot precisely the same as a cold one. I am just not persuaded that heat causes any harm. My view is that past the first shot some heating is always present. More uniform groups seem likely when the heat has somewhat stabilized. It is easier to maintain a barrel's heat than to restore it to an unfired cool temperature.

At any rate, I am new to this. Teach me!

 

[Az'92]

I have read that temperatures of the burning propellant can reach over 3000 degrees. The surface of the bore just forward of the chamber is eventually worn away from the combination of high temperatures and friction. Shooting a lot of rounds in a short time exacerbates this normal wear.

 

[nachogrande]

caliber, hot/mild load, pencil thin vs bull bbl?

For a new/good/expensive gun for me, cup of coffee hot. Too hot to touch at all in any gun for me is too hot, but some guns like AK's, it's kind of a fact of life.

 

[Sus Scrofa]

I am with Mike G on this. I never shoot more than five rounds in a string when prepping a rifle for hunting. I'm not into punching paper. I want my rifles to shoot the best group I can load for, then to put that group 1 1/2 inches high at 100yrds(all calibres) that means I never hit low at my normal sensible hunting ranges. If you enjoy just shooting at targets then that's fine, but I would still go with the five shot string, even reduce this to three shots in some rifles. I had a very neat little 7x57 which had a VERY lightweight barrel. The whole rifle was like a feather to carry. That rifle would put two rounds almost through the same hole, then gradually start to climb up and in a curve to the left. Consequently I never shot more than two rounds at a time and let it lie to cool, but normally I only needed one shot to check it was still spot on. Our big heavy bull barrelled Parker Hales back in the 80s would handle heat better but we very rarely shot more than a five shot string with them(308Wins) my rifle was still shooting sub moa after 12yrs of monthly practise days, when I retired. Of course that one good cold shot was what we were looking for back then too as it may save someones life. I think rather than trying to work out what temp., a barrel burns at, it would be better to get that one cold shot sorted first.

 

[rojkoh]

Thanks for the response MikeG. Have been working on the floating. It this point still reducing foreend pressure. I use all of my guns for both target and hunting. Both hot and cold barrels. The Husky is the only one that has given major PA to PI changes with temp changes. I at least have an idea what the others do as barrel temp changes. The Husky is all over the map, but is improving as the forearm pressure comes down. Living on a boat in BC with the hunidity changes does not help.

I am still interested in the subjectives on when to switch rifles due to barrel temperature while at the range.

There are reasons some rifles shoot better when warm, the heat of the barrel/chamber can affect the ammo.

 

[Purist]

Kos, you are correct concerning annealing temp. You are also correct that at some point the bore opens up (coefficient of thermal expansion). However, the assumption that is often made is that the barrel heats uniformally. In reality, it heats from the inside out meaning that the material near the bore is expanding faster and being restricted by the material near the outside of the barrel. There is a temperature range where the material actually begins to expand into the bore prior to opening up. Look up "maximum material condition". If you fire a few shots, let the heat equalize, fire a few more, and so on, you are less likely to cause excessive wear even if it is hot rather than heating it rapidly by shooting larger strings.
You will notice that after repeated trips to the range, the barrel heats slower with larger strings due to reduced friction. The wear is still there, but is for lack of a better term, controlled.
In addition, when the barrel is drilled and heat treated during manufacturing, internal stresses can be introduced. Heating and cooling the steel relieves those stresses ( a process called normalizing). This moves or warps the steel " permanently ". In a part that needs to be very precise, you would leave machine stock, normalize and heat treat, or just heat treat, then finish machining or grinding after. This is not practical for a barrel. So you can distort the barrel by repeatedly getting it too hot, then cooling.

 

[Sus Scrofa]

Blew out a few 30-30s to 7-30 yesterday; only ten rounds but did them in two fives. If the outside of the barrel is HOT then how hot is the steel in the throat area ????? Best to be prudent in my view.

 

[rojkoh]

How hot is

Simple solution if you want to either cool down the barrel or shoot groups with a cool barrel in between, jut get a cleaning rod and use it as a heat sink.

 

[broom_jm]

Simple solution if you want to either cool down the barrel or shoot groups with a cool barrel in between, jut get a cleaning rod and use it as a heat sink.

How does one use a cleaning rod as a heat sink? Just rub a wet swab or two down the barrel?