Rifle Barrel Heaters For Match Shooting

[Mike1234567]

I don't compete... was probably never good enough and have shaky hands now. But I'm just curious about something.

Point of impact changes as barrels go from cold to hot, right? Does anyone use a barrel heater to keep their barrel from getting too cold between rounds? It seems even a better idea in extremely cold weather. Is that a bad idea due to possible overheating after several rounds?

Sorry if this is an old or silly idea. Curiosity gets the better of me sometimes.

 

[243winxb]

Barrel Heat

Good question. Wonder what others will have to say. Custom barrels dont seem to change impact on heating as much as factory barrels. I guess it depends on how much. Factory barrels i have seen can move point of impact as much as 2" @ 100 yds when they get hot. Some benchrest shooters pour water down the barrel to cool it.

 

[MutinousDoug]

My AR based match gun shoots the same zero after a 10 shot rapid as it does cold but ammunition is definitely sensitive to cold temperatures as well as heat. I keep mine in an insulated lunch bag when I shoot a match.

The current .22lr ammo I'm shooting shoots about 1" groups at 50 yds through my 10-22 at "normal" temperatures but when it gets much below freezing the groups open up to 2" and the zero changes. I try to keep a magazine in my pants pocket when I'm hunting.

 

[Comrade Mike]

Changed in ammunition can be roughly accounted for by the ideal gas law (propellant gasses are far from ideal but it will illustrate the point)

PV=nRT. Your case volume is constant, your moles of gas are constant, the ideal gas constant is constant (duh). So given an extreme drop in temperature you'll lose pressure behind the bullet this potentially losing accuracy.

As far as barrel heaters go. I'd think you would need something more along the lines of a barrel heat exchanger. Something to equilibrate the temperature of your barrel whether it's warming or cooling.

 

[Mike1234567]

Okay, yeah... ammo heaters too??

 

[Soupy44]

I shoot smallbore prone and 3P matches. I've shot a few matches at or around freezing, and I didn't notice much of a change in accuracy. My first shot is always at 4 or 5oc about an inch or two. I have a slight memory that maybe it took a shot or two extra to stop getting my cold barrel impact, but I can't confirm that.

I've never heard anyone talk about issues shooting in cold weather, but I just shoot smallbore at 50y, 50m, and 100y. Might be different for high power.

 

[Comrade Mike]

I shoot smallbore prone and 3P matches. I've shot a few matches at or around freezing, and I didn't notice much of a change in accuracy. My first shot is always at 4 or 5oc about an inch or two. I have a slight memory that maybe it took a shot or two extra to stop getting my cold barrel impact, but I can't confirm that.



I've never heard anyone talk about issues shooting in cold weather, but I just shoot smallbore at 50y, 50m, and 100y. Might be different for high power.

The issues are there but they're pretty minimal at short range. One thing to be aware of though is the opposite happening. Shooting hot rod reloads in 100+ degree heat when developed in 75 degree weather can cause an over pressure situation.

 

[Sav .250]

Barrel heater ? Now that would be a first.

 

[Comrade Mike]

Good question. Wonder what others will have to say. Custom barrels dont seem to change impact on heating as much as factory barrels. I guess it depends on how much. Factory barrels i have seen can move point of impact as much as 2" @ 100 yds when they get hot. Some benchrest shooters pour water down the barrel to cool it.

Custom bull barrels basically act as giant heat sinks. You have more mass to distribute all the heat over this mitigating the effects of barrel heat

 

[Plastikosmd]

For some of the VV loads for my 50 bmg, it is said that The ammo should be heated for best results. Haven't tried that yet

 

[MutinousDoug]

Rifle Barrel Heaters For Match Shooting
Changed in ammunition can be roughly accounted for by the ideal gas law (propellant gasses are far from ideal but it will illustrate the point)

PV=nRT. Your case volume is constant, your moles of gas are constant, the ideal gas constant is constant (duh). So given an extreme drop in temperature you'll lose pressure behind the bullet this potentially losing accuracy.

As far as barrel heaters go. I'd think you would need something more along the lines of a barrel heat exchanger. Something to equilibrate the temperature of your barrel whether it's warming or cooling.

For the Ideal gas law to be applicable, total energy must be conserved, I grant you that. In the case of firearms, uniform ignition and efficient propellant burn are as critical to uniform downrange performance and application of the law as is total energy applied to the projectile.
A pressure/time trace of 100% propellant burn may well show an equal amount of force under the curve even though the burn may start slow and gain pressure as time goes on, while an equal force with the pressure peaking early on and then degrading may have a significantly different effect on a bullet as it is forced down rifled barrel.
So the Ideal gas law needs to incorporate a "time vs volume" coefficient, at least, to apply to firearms accuracy (as I think the OP expressed an interest in)

 

[Mike1234567]

I didn't know the physics of it but, yes, that's what I meant. I also see the need to cool the barrel, as another poster stated. Too, the ammo should be heated or cooled as yet another posted stated.

So... temperature "stabilization" of both barrel and ammo... would be beneficial to accuracy.

 

[627PCFan]

"Custom bull barrels basically act as giant heat sinks. You have more mass to distribute all the heat over this mitigating the effects of barrel heat"

Dont assume that always works. I have a 26" ER Shaw Full Bull Barrel that starts patterning after 5 rounds. Its a 9lb hunk of steel and that's about it. You get what you pay for

 

[Laphroaig]

The bottom line is that a rifle that changes point of impact with barrel heating isn't a very good target rifle. Most military rifles and championship level target rifles don't have that problem. Rather than cool or heat barrels, most serious competitors would probably replace that rifle.

An exception is the M1 Garand. Both of my rifles have had episodes of impact changes due to heating. The culprit is generally the op rod rubbing on something which needs to be identified and relieved somehow.

I do try and keep my ammo at a reasonable temperature during a match, usually by keeping it out of the sun. I've seen others bring a small cooler to a match.

Laphroaig

 

[wanderinwalker]

As has been said, I've never seen anybody warming (or cooling for that matter) a rifle barrel during a match. But I only shot Highpower, so our accuracy standard was only a 1-MOA X-ring, not bug-hole groups.

If I had a "match" barrel that strung groups noticeably due to barrel heat, it would get tomato staked pronto. In shooting 600-yard slow fire I've both used the entire 20-minutes/20-shots time and run off all 20 in about 9 minutes (this requires steady conditions and can be hard on your target puller if he/she isn't expecting it ). My AR-15 shoots the same over the string using either approach.

Now ammunition can be temperature sensitive as all get out. I stopped using 748 for .223 match ammo for just this reason. Varget on the other hand ran to the same zeros from 20* to 105*.

 

[jcwit]

I'll throw in another variable in. Hot summer day, sun beating down on one side of barrel. Metal on that side expands from the heat thereby slightly bending the barrel towards the shady side????????????????????????????????????????

 

[Comrade Mike]

For the Ideal gas law to be applicable, total energy must be conserved, I grant you that. In the case of firearms, uniform ignition and efficient propellant burn are as critical to uniform downrange performance and application of the law as is total energy applied to the projectile.
A pressure/time trace of 100% propellant burn may well show an equal amount of force under the curve even though the burn may start slow and gain pressure as time goes on, while an equal force with the pressure peaking early on and then degrading may have a significantly different effect on a bullet as it is forced down rifled barrel.
So the Ideal gas law needs to incorporate a "time vs volume" coefficient, at least, to apply to firearms accuracy (as I think the OP expressed an interest in)

I'm well aware of this. I mentioned the system is far from ideal. Its just to illustrate a point.

 

[spitballer]

No doubt about it, temperature has a profound effect on accuracy and point of aim. I generally load for a hot barrel when shooting at the range, although on occasion I have loaded some hotter rounds to start with. And of course, there are the fouling shots - I usually need two - that are going to fly no matter how they're loaded. Cooling the barrel with a water jacket using a reef tank chiller might be an idea, but I'D probably get laughed off the range, not to mention disqualified from competition. A stick-on tape thermometer might be helpful, though.

 

[Trent]

My F-Class rifle doesn't change point of aim as I go from cold to hot from shooting.

Neither does my SCAR17 and it has a factory barrel.

Today it was 17F with 14" of snow on the range at our High Power / Smallbore / F-Class shoot, everyone that shot (even 20 round strings) were doing just fine with no point of aim shift.

Various AR's, Savage factory rifles, even an Anschutz was there today.

You learn by doing. So go do, and find out!



http://www.thehighroad.org/showthread.php?t=739512

 

[Comrade Mike]

Trent you're a braver man than I. I'm cold just looking at you

 

[Trent]

Preparation man. That's all you gotta do. I wasn't really cold at all - added and removed layers as the day went on as appropriate.

TEST your gear. Sit out on the front porch in a cold snap of the right range with your gear on and watch a movie on Netflix or something. 2 hours in, you'll KNOW what isn't working.

Then go for a hike or 2-3 mile walk, and figure out what you have to adjust when you are under exertion. Can you remove layers to keep from sweating?

Test it out under the conditions you'll be in, and you'll be just fine. And bring a poncho outer layer in case of wind/rain/snow/sleet/etc.

 

[dmurdach]

not a thermometer but

Its definitely not a target rifle, but I painted the compensator of my hi-point 995 carbine with a temperature sensitive paint. Just did it for kicks no real reason. At about 90 it changes from black to a light grey, there are other temp ranges so even a little pinstripe of this for the appropriate temperature would be a good indicator of barrel getting to hot and was likely to start stringing shots, or when it had cooled down enough to resume.

 

[thegiff]

My first comp rifle walked when shooting, bedding it fixed it. My current comp rifle has never walked shots around.

If you are using a temp sensitive powder, then you need to characterize your velocity and impact point with ammo temp. I've seen a load go out of tune between hot and cold, it was in tune when warm and shot terribly when cold (happened to be Prvi Partizan 308 match ammo). If using something that is much less temp sensitive like Varget or H4350 or H4831SC, then at least for my practice and comps so far I've not noticed a change in velocity or in impact point.

I've speculated that a warm side/cold side from the sun might bend a barrel. I once poured some liquid nitrogen on a sheet of plastic, it was about 2foot X 4foot. It curled up into sort of a bowl shape, enough so that each end the long way was about 1 foot up.

Maybe to test this on a barrel, leave it in the sun for a while. Shoot a group. Cool one side with ice and shoot a few more shots.

My bro and I both shoot tactical comps, we've had our barrels too hot to touch with no noticeable change in impact point. So far every time (since bedding I mean) I've thought my point of impact changed I had found that I was holding the rifle different and causing the shots to walk.