08-20-2018, 11:28 PM
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'.
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'.