Keeping the Grendel cool at the range

[LR1955]

I am a little confused (nothing new) here. There is no question that some barrels will shift their POA when they are hot. Pencil barrels do it more than bull barrels. Got that. But am I reading that a hot barrel erodes the barrel throat at the same rate as a cool or cooler barrel? LR55... is that what you are saying? Or is it a matter of degree that is a lot less than normally assumed? Or are you saying a chamber/barrel fan is not effective?

Thank you. Looking forward to responses.

GM:

If you shoot nothing but sustained or rapid fires, the throat will erode faster than if you shot slow fire. How much faster? I would say you will get 35% less shots before the throat is so far gone that not even shooting longer bullets will do any good. How much will accuracy decay? Enough that your X count and then your score drops at 600. I think that bearing surface of the bullet has as much or more to do with throat erosion as the heat produced by various powders so longer bullets will abrade the throat faster than shorter ones.

So when I say 'after 6 or 8K rounds with the Grendel, just get a new barrel', I am saying under normal use which means that sometimes guys will shoot sustained fire and other times slow fire. Most guys here do not shoot automatic fire and if they do, they are shooting at close ranges where the only thing that counts is that the carbine functions perfectly.

If your accuracy is degrading as your barrel heats up, and you can prove that it is due to the barrel, my advice is to get a quality barrel that can withstand the heat produced from normal shooting.

Even pencil barrels, if made well and heat treated properly, will hold a zero when hot. Unless they are so thin that they are dangerous without even getting hot. Fluting will probably help with stiffness when using a real thin barrel so if a guy really wants a thin barrel, I would advise he gets it fluted.

As for chamber fans. A fan will surely cool it down faster than letting it just sit there. The question is, does it matter? It won't help a poor barrel, poor loads, a poorly made rifle, poor sighting system. It won't help mirage, wind doping etc. It will blow barrel mirage away which I will say is a good thing. Except those little fans will only blow a short section of the mirage away. A mirage screen goes the whole length of the barrel.

You are more likely to shoot better in very hot conditions if you have the fan turned on you to keep you comfortable than blowing air through the barrel.

Here is what you can do though. Buy one of those Radio Shack indoor / outdoor pocket thermometers and run your own test to see how hot the chamber gets when shooting and if that heat has any effect on performance when shooting as you would in a normal range session.

LR

[Gusmeister]

Hey LR,

Thank you for your very enhanced reply. I was not quite getting your perspective before. Now it's pretty clear. I was never a target shooter of any formal sense. But your comments remind me of the ones I have known. The bought good barrels, shot the heck out of them and were quick to replace them as soon as accuracy dropped off enough. Similar.

Thanks again

[Klem]

Cooling the barrel is in the interests of both accuracy and barrel life, but how much so depends on a few things.

Barrel thickness. There's no doubt that thicker barrels act as better heat-sinks than thinner barrels. They also make for stiffer barrels which resist warping when they heat up. Pencil barrels display vertical stringing as they heat up, which is the cost of having a light rifle. If all you are doing is hunting then fine, but sustained small groups and competition won't work. 55' mentioned the Palma profile. I have several Palma's and they come in three thicknesses; Light, Medium and Heavy. After shooting all three I honestly cannot tell the difference in accuracy between the weights. It probably exceeds my ability to shoot. My latest 6.5*47 barrel is a Light Palma from Krieger. If you get onto Krieger's website you can see charts of different profiles like Taper, Bull, Palma etc. In AR barrels there is less choice of profile and as for how efficient a heat sink various profiles are is not information I have come across. Do you buy a fluted barrel and hope the extra surface area of the flutes exchanges heat with the atmosphere more efficiently than the amount of heat-sink metal you have shaved off...It's an experiment for someone I guess. What I do know is that fluted barrels are no stiffer than unfluted (all things being equal, like barrel profile). Fluting is a way of making the barrel lighter and nothing more than that. The Lilja M4 Navy 223 is 2.18lbs unfluted compared to 2lbs fluted, so not a lot of weight reduction for the extra cost when you think about it.

If you can blow or channel the heat mirage away from the top of the barrel then that is a known factor in accuracy. Barrel screens are a regular sight at Bench Rest shoots. If you want to see barrel mirage in action shoot at night with no wind. The lit target shimmers and boils and this has got to affect accuracy as the cross hair wobbles around with the mirage. A light breeze blows over the firing point and the mirage goes away. A fan will no doubt mimic that effect so while it might not cool the barrel efficiently is certainly will blow the hot air coming off the barrel and in front of the scope away.

I have never used them but I don't expect those chamber fans will be of much use for the effort. If they were everyone would be using them. No doubt they do cool the barrel but not enough to make much of a difference unless you plan to be at the range all day.

One last thing. Full-auto fire is the quickest way to turn your barrel into a smooth-bore known to man (except maybe a line of det-cord down the barrel). I have seen this in the military. Undisciplined full-auto fire and the barrel is smoking. There goes any competitive advantage you might have had in accuracy. I had a pencil barrel AR which was for funnsies. It quickly became a 3MOA gun with full-auto fire but it sure was fun to shoot. That was a long time ago and 'those were the days'.

[Gusmeister]

Thank you for your input and knowledge Klem. The best barrel "cooler" I Know of is shooting on a 30 degree day. I can just shoot and shoot and shoot (not rapid fire of course) and the barrel just gets warm. Quite the opposite on a 90 degree day. By extension then... a chamber fan that is blowing ambient air down the bore is like a "for a human" fan on a 90 degree day vs air conditioning on a 90 degree day. The fan is better than nothing but in no way compares to cooler air.

[LT Dann]

Thanks a lot for all the info guys! I finally found a load that the Grendel likes. I shot 5 waited 10min, and used a chamber chiller. My goal was to keep the barrel cool enough to hold it. Seemed to really kept an even barrel temp. Not sure how much that mattered, but finally I’m seeing potential out of this BCA upper!
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[mdewitt71]

Wife got me the BarrelCool for my Bday yesterday....

http://barrelcool.com/product-category/barrelcool/

I will say from first glance and turning it on out of the package, I am not impressed at all.
The fan that is on it is way smaller than even a CPU fan (about the size of a dime); I can barely feel the breeze out of the tube end.

I have not taken to range or put it in a hot barrel or chamber but, hopefully will try it out Friday.
Right now I am skeptic on thinkin this version is more of a gimmick.

[CazadorBob]

Wife got me the BarrelCool for my Bday yesterday....

http://barrelcool.com/product-category/barrelcool/

I will say from first glance and turning it on out of the package, I am not impressed at all.
The fan that is on it is way smaller than even a CPU fan (about the size of a dime); I can barely feel the breeze out of the tube end.

I have not taken to range or put it in a hot barrel or chamber but, hopefully will try it out Friday.
Right now I am skeptic on thinkin this version is more of a gimmick.

I have not tried it myself, but I have heard of guys who keep a bore snake inside of a ziplock bag in an ice-filled ice chest. In between strings they pull the cool bore snake into the barrel and let it sit for a bit. Might be worth a try,...

[Bigs28]

https://www.area1sports.com

[RANGER]

Thanks for the info guys!

I read an article recently that talked of how hot the expanding gasses are; way hot enough to melt barrel steel. We're lucky that the bore is only exposed to those temps for milliseconds at a time.]

Plasma cutter effect....and seen in suppressors that are subjected to heavy volume of rapid fire. The baffles can often look eroded near the bore hole....because they are.

Lots of good advice as far as keeping the bolt open, practice precision early in the range session and development drills later, and waiting a good long time between strings.

When I was on a sniper team and we would have a session practicing "Cold Bore Shots" I would dread them because they were super boring. Lots of down time and chatting waiting for the rifle to "reach equilibrium" in the temp. One thing I learned though (at least it seemed to me anyway) is the rifle heated up easier than it cooled down***. So I would use a mist spray bottle and cool the barrel. Then I'd stick it in the front seat of my car with the A/C cranked up. After it cooled down I'd run a patch in the barrel (to wipe out the condensation if any) and wipe the outside as well. Bag it up, put it in the trunk and wait another 10 or so minutes. (Our bags were stored in the trunk and this was the most likely realistic temp for cold bore).

Like I said, tedious and boring. Lot of work to figure out where your stick shoots cold. But then again, it's really important to know that when a slight miss can be "two million dollars to the left". (at 100yds my cold bore was not quite 1/2" high and to the left from POA. The next 4-5 could clover leaf POA/POI)


***EDIT: for clarification, I meant the rifle would go from "too cold" to "just right" a lot easier than "too hot" to "just right"

[RANGER]

oh, forgot to add that sometimes I'd just hang a moist rag on the barrel for a bit. Let it reach equilibrium for a minute or two then start shooting again.


One last thing that I may have missed if someone mentioned.....ammo. We found out by accident that ammo left in the sun can shoot much different than ammo sitting in either a cold trunk...or crazy hot trunk. You may have started your range session out shooting one way and later that day shot a little different....not realizing your ammo has been sitting on your shooting bench all day in the sun.


Keep your ammo in the shade in an ammo box.

[Trapper]

This is a you tube video of the barrel blizzard. It works as well as any of the others, but it has 360 degree adjustable fans that you can rotate to cool your face while shooting and cool the barrel while not shooting. Plus it uses a great rechargeable usb battery that you can recharge in the truck if needed. Hate to sweat profusely while on the line.
https://www.youtube.com/watch?v=CUvHhENiE-Q

[Belt Fed]

I bought one of these, it seems to work well. I usually put it in and turn on while I go to target. It's made to lock up in an AR15, but it will work on the AR10's too. it won't lock up but just stick in the magwell and it works. I bought it on sale at another site at a lot better price than this one.

https://www.opticsplanet.com/caldwell-ca...e9e5234b96