Barrel heat management in F-TR

[Turbulent Turtle]

Thicker barrels will always heat-up at a slower rate than their thinner counterpart. Thicker barrels also give-up that heat at a slower rate. As the surface of the thicker barrel cools, that loss of heat is quickly replaced with the heat migrating from the center of that steel. A thinner barrel will always cool at a faster rate.

The operative words in my comparison of the cooling rates of thick versus thin barrels are: "FOR THE SAME AMOUNT OF ROUNDS IN THE SAME TIMEFRAME." Thick cools faster because of the increased surface.

If I compare the cooling rate of a thick barrel at say 190degrees compared to a thin barrel also at 190 degrees, that is meaningless to us. But if I compare a thick barrel through which 22 rounds have been fired in 12 minutes to a thin barrel through which 22 rounds have been fired also in 12 minutes, you will see that the thick barrel will be back to local conditions faster than the thin barrel. There's the added bonus that the thick barrel did not get as hot as the thin barrel.

 

[Ned Ludd]

The operative words in my comparison of the cooling rates of thick versus thin barrels are: "FOR THE SAME AMOUNT OF ROUNDS IN THE SAME TIMEFRAME." Thick cools faster because of the increased surface.

The cooling rate is based on the surface area:volume ratio of the barrel, not just the surface area. The surface area:volume ratio for a thinner contour barrel will be notably more favorable for cooling than the heavier barrel, but as you pointed out, the thinner barrel will reach a higher temperature for a specified number of shots. The thicker barrel will both gain and lose heat more slowly, but doesn't have as far to go to cool down to ambient temp because it doesn't heat up as much to begin with.

In a match, the barrel is going to heat up no matter what you do, because we have to shoot at a rate that doesn't allow complete cooling in between shots. However, unless you have to shoot again immediately, the 30 min or so between relays is usually enough to bring the barrel temp back down. So I'm usually more concerned with how high the temperature goes, less so with how fast it cools off. In this regard the heavier contour barrel wins hands down. The heavier barrel is also less likely to undergo major shifts in POI as it heats up.

 

[Jennb]

Thank you, I guessed I missed that. I do have to give the rain cover a thumbs up, more than just a little thought and some effort went into that. I was wishing for a tent!

I was wishingfor a tent also. The person with the tent was ultimately disqualified because of his front rest was not legal

 

[clunker]

I remember researching the barrel thickness topic a while back. It is hotly debated, but the best scientific explanation I could find suggested that given the same number of fired rounds, both rifles will return to ambient temperature at the same time. The thinner barrel heats up faster and cools faster. The thicker barrel has a lower peak temperature but takes longer to cool. Of course, this is only true to a point. If you were to fire an infinite number of rounds, both barrels would reach the same maximum temperature (and both would most certainly be destroyed in the process).

If the ultimate question is, which one returns to ambient temperature faster, then it's a wash. But that isn't really what's important when we're talking about F-TR. The real question is, can a thinner barrel cool quickly enough between rounds to compensate for its rapid increase in temperature compared to a thicker barrel. The simple answer is "no."

If I can get through one season with the stock barrel, and I really like the sport, I will eventually invest in a more suitable barrel and a heavier stock. Not an option for next year.

 

[Medic505]

I was wishingfor a tent also. The person with the tent was ultimately disqualified because of his front rest was not legal

Ok, I know zip, nada, nothing about open class other than I won't or don't want to shoot open because I don't want to haul around a 77 pound front rest. (and I know, Danny Biggs shoots off a bipod at times, but Danny could beat 90% of the field with a couple sticks and some string for a front rest) But I have to ask, what makes a or any rest in open class illegal? A computerized weather/GPS/guidance system???

 

[Jennb]

The rest had no sort of bags in it and the new rules state that the rest must have bags that can be deformed with your fingers. Not sure exactly how that reads but his rest was solid material.

 

[Medic505]

The rest had no sort of bags in it and the new rules state that the rest must have bags that can be deformed with your fingers. Not sure exactly how that reads but his rest was solid material.

Hummm...OK. Well, I guess that's something else I don't have to worry about. Thanks Jenn

 

[Turbulent Turtle]

Yeah, it's a new rule for F-Open, gotta have a bag on the front rest and then this gem:

Rule 3.4.1.a

"(8) The contents of front and rear bags will be dry, finely divided (less than 5mm/0.19”) granular substance such as, but not limited to, sand, gravel or grain, packed loosely enough so that the bag will be visibly deformable by pressure of the range officer’s fingers.."

The double period at the end is in the rules. It must mean it's really important.

As a part-time match director, I now have to inspect the contents of the bags of the F-Open folks and measure the substance therein.

This could get sticky.

Next up the rules for the new discipline under Rule 23. My AR-10 is having problems getting down to 14 pounds. There are many other rules for that one. Sigh.

 

[Jennb]

I remember researching the barrel thickness topic a while back. It is hotly debated, but the best scientific explanation I could find suggested that given the same number of fired rounds, both rifles will return to ambient temperature at the same time. The thinner barrel heats up faster and cools faster. The thicker barrel has a lower peak temperature but takes longer to cool. Of course, this is only true to a point. If you were to fire an infinite number of rounds, both barrels would reach the same maximum temperature (and both would most certainly be destroyed in the process).

If the ultimate question is, which one returns to ambient temperature faster, then it's a wash. But that isn't really what's important when we're talking about F-TR. The real question is, can a thinner barrel cool quickly enough between rounds to compensate for its rapid increase in temperature compared to a thicker barrel. The simple answer is "no."

If I can get through one season with the stock barrel, and I really like the sport, I will eventually invest in a more suitable barrel and a heavier stock. Not an option for next year.

For the most part cooling time of a barrel in F Class is revelevant because other relays generally shoot between your rounds giving ample time for cooling unless you live in an area where extreme heat and relative humidity play a big role in cooling time.

I shot on an open team a couple years ago at Bergers on same time frame with same rifle as my shooting partner. He shot, we cooled barrel with towels that had been in ice water then I shot once it was cool. Still had time left over. It was fun and wuite exciting watching people figure out what we were doing!

 

[memilanuk]

For the most part cooling time of a barrel in F Class is irrelevant.

FTFY

More than a few years ago, we had a team match where one shooter had a gun/load was questionable, so we were just going to double up on my gun. First shooter, then the guy on my gun, then pit change, then our third shooter, then me to close out. Good plan... except the third shooter got a couple shots into his string, and blew up a bullet. And then another. So he finished up with my gun. Ended up having *three* out of four shooters shooting *one* gun... in Raton, in September... *that* was one damn hot barrel!

More applicable to @clunker is that the Spokane gun club shoots (or at least used to) a weird format of 2x300 and 2x600. My relay was in the pits first, and the relay on the line shot two relays in a row @ 600yd. Then we came out, and we shot two in a row. As in, shoot one string, get up for about 10 minutes, then lay back down and shoot the second string. Then we drove our vehicles down to 300, and I started to head for the pits but no, we shot both 300yd strings back to back first. Then the pit change, and the first relay shot their 300 strings. Weirdest damn relay configuration I've ever seen. And that barrel, after shooting 88 shots in under an hour and a half, in *August*, was probably hotter than I've ever gotten a bolt gun before or since.

 

[Jennb]

FTFY

More than a few years ago, we had a team match where one shooter had a gun/load was questionable, so we were just going to double up on my gun. First shooter, then the guy on my gun, then pit change, then our third shooter, then me to close out. Good plan... except the third shooter got a couple shots into his string, and blew up a bullet. And then another. So he finished up with my gun. Ended up having *three* out of four shooters shooting *one* gun... in Raton, in September... *that* was one damn hot barrel!

More applicable to @clunker is that the Spokane gun club shoots (or at least used to) a weird format of 2x300 and 2x600. My relay was in the pits first, and the relay on the line shot two relays in a row @ 600yd. Then we came out, and we shot two in a row. As in, shoot one string, get up for about 10 minutes, then lay back down and shoot the second string. Then we drove our vehicles down to 300, and I started to head for the pits but no, we shot both 300yd strings back to back first. Then the pit change, and the first relay shot their 300 strings. Weirdest damn relay configuration I've ever seen. And that barrel, after shooting 88 shots in under an hour and a half, in *August*, was probably hotter than I've ever gotten a bolt gun before or since.

I have shot numerous back to back strings with around 10 minutes between. That is when a barrel cooler or iced wet towels come in real handy. Have not had a hot barrel effect accuracy but you sure dont want to grab barrel afterwards.

 

[Don_Parsons]

A Coalman high flow battery air mattress pump for $20 or a water bottle to kool things down.

Both are quick and fast as it helps prolong the barrel life,,, I like the Coalman air flow pump since it kool the barrel down pretty fast.

Open bolt handle, lean nozzle into chamber area, and your good to rapped fire the next string.

About 1 to 2 minutes per kool down time, some shooters use a plastic hose to direct the air flow into the barrel, I get the same results using just the pump.