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Posted: 5/19/2005 5:57:09 PM EST
Stainless for accuracy, heavy for stability, chrome lined for reliability.......

I got the basics, I think. But, now I am wondering about heat and how a barrel holds its accuracy.

Currently, my main varmint rifle has a 20inch heavy stainless barrel. It shoots in the legit .3's when its at a good operating temp---say the first 20 rounds or so. I don't bump fire or blast away, but, when we're lucky, we'll have lots of prairie dogs in front of us and we can keep up a pretty steady pace--3-5 shots a minute or so. After a few minutes, that stainless barrel is heated up pretty good and it will then hold that heat for a while too!! Once she gets hot, the accuracy really starts to drop off.

So, what weight, material and contour gives the best combination for a barrel to keep its accuracy while shooting under such a load??? Does the length of the gas system matter???? Does one run "hotter" or cooler than others????

THanks guys
Link Posted: 5/19/2005 9:35:52 PM EST
Heat will affect the match-grade SS barrels the most, but every barrel has it's own characteristics. Having a fluted barrel will help that SS cool off a lot faster, make it lighter too. Chrome-moly won't be affected as much, but still it will be to some extent. Light barrels cool off real fast but accuracy goes out the window when they heat up, sometimes after only 5 shots or so. Also when a barrel is hotter, copper fouling will embed into the rfling better, thus further reducing accuracy. Heat is probably one of your worst enemies. The best thing for volume shooting would have to be heavy stainless fluted. Perhaps have a seperate upper assembly to swap out that is identical to the other for alternating and letting them cool. Most diehard prairie doggers take several guns anyway.
Link Posted: 5/20/2005 2:16:24 AM EST
An aggressively fluted barrel will help a lot. Much of barrel heat comes from the friction of the bullet being forced down the barrel. When I switched to shooting moly-coated bullets for prairie dog hunting, the difference was noticeable. The moly-coated bullets will let you shoot more with less heat than non-coated bullets.

I know there is a lot of debate that goes on about both barrel fluting and moly-coated bullets. I have been prairie dog hunting extensively for about 25 years. I have shot hundreds of thousands of rounds over the years, about half of it moly-coated, and it does make a difference. When I clean my upper, after a big prairie dog hunt, all I use is a couple of patches, no brushes, and I don't have any copper fouling. Many times I have 800 or more rounds through an upper between cleanings. They still shoot bug-holes and they clean up in minuets.
Link Posted: 5/20/2005 2:41:29 AM EST
Dtech1 :
Not to get away from the topic, but you brought up moly coated bullets. I understand that there is a brake in procedure for moly what works best for you.

Thanks
Joe
Link Posted: 5/20/2005 6:56:44 AM EST
[Last Edit: 5/20/2005 6:57:25 AM EST by Zak-Smith]
If we are talking about the barrel itself (ie, no poor fit with the upper receiver, no ammo problems as the powder preheats in the hot chamber, etc), then there are basically two ways heat affects the accuracy (ie, ignoring long term effects like throat erosion):

1. Heat will raise the temperature of the barrel at a rate inversely proportionate to the mass of the barrel

2. As the barrel temperature rises, any stress in the steel will manifest as warping. A stiffer barrel will resist warping better.

Which suggest the following:

A. Have a barrel whose temperature rises more slowly, the most obvious method being to increase its mass.

B. A thicker barrel profile will be both more massive and stiffer, so it will both heat up slower and stay stiffer

C. Avoid machining operations on the barrel blank which tend to leave more residual stress in the barrel.

On point C, fluting can produce a lighter barrel as stiff as a heavier barrel, but if the fluting has left stress in the steel, the benefit may be defeated.

So if you absolutely want the most heat/temp stability, get a thick barrel from a top tier barrel maker (e.g. Krieger) and don't have it fluted.

-z
Link Posted: 5/20/2005 7:02:15 AM EST
You should take a look at this thread

Pricey, but someday I will have one!


Link Posted: 5/20/2005 8:36:16 AM EST
You are right on. As a former tanker, accuracy went up with tank barrels when they insulated them and retained the heat. In this instance, accuracy was paramount out past 2600+ meters. The same theory should hold for a rifle barrel.

Beyond that the heating and cooling cycle of various metals gets into some fairly complex metallurgy, especially in the field where nothing is predictable. On a range where things are somewhat more predictable this is probably more critical.
Link Posted: 5/21/2005 4:22:06 AM EST
Three to five shots per minute shouldn't heat a heavy 223 barrel enough to cause accuracy problems. In High Power matches we shot (Regional Course) two (2) ten shot strings of rapid fire (each string in 60 seconds at 200 yards and 70 seconds at 300 yards) and accuracy was unaffected. The barrels get plenty hot doing that. This is shooting CMP legal AR15s. I'm wondering if mirage isn't causing you some problems? Just a guess.

Good shooting,

Phil
Link Posted: 5/21/2005 11:23:57 AM EST
Phil, your right....

Where were shoot, out near the South Dakota Bad Lands
mirage sucks,
wind sucks

the only thing worse is windy mirage which really sucks.......

Thanks for all the info. I was hoping that I could find some perfect combo of barrel length, contour, material and gas length system that would minimize the effects of heat and wouldn't weight a ton...........guess there isn't unless I can shell out the 500 bucks for the "magic barrel".......maybe someday. Till then, I guess I'll stick with my stainless bull
Link Posted: 5/21/2005 2:34:31 PM EST
Hi ker2222,

Lucky man! I love the Badlands, been there once and I promised myself that some day before I die I would spend a month or so there with a few cameras and a cooler full of film. Beautiful area. Where do you hunt, my buddy goes out to SD every year for a big prairie dog hunt. I think he goes for at least a week or two. Ships his rifle and ammo out via UPS prior to flying out, rents a car or truck, and has a ball. He keeps trying to get me to go, if only the financial gods would smile on me I'd love to. What upper are you using? RRA has a stainless heavy barrel varmint upper that is 24" long and 1.050" under the tube handguard and .920" forward of the gas block. Thats my next planned buy if Santa is really good this Christmas.

Cheers,

Phil
Link Posted: 5/21/2005 5:31:28 PM EST
I've got relatives that live in Pine Ridge, so we travel all over the reservation near the badlands--we take two or three week long trips in the summer and one in the fall and one in the spring. We have a blast. We have shoot everything from ak-47s to black powder replica muzzleloaders at the little pox carrying vermin.....

When serious though, I shoot a DPMS 20inch SS heavy barrel upper. It shoots awsome--when I do my part which isn't really all that often. I also have a rem 700 bolt action being fitted with a custom 243win barrel for the real long shots in the wind. I now have my eye on trying to put together an upper that will be a little lighter and balance better than the DPMS upper. 20 inches is nice, but a longer thinner barrel--like the bushmaster varminters balance way nicer. And, a shorter barrel, like a nice 16 inch recce from GTS would handle better as well. Hell, truth is, I like the building and rebuilding set-ups as much as I like shooting them!!!!!! So, I think a new upper is in my future....

Here are some pics

???????????guess I can't post pics anymore, the button is missing from my writing window??????
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