MnYoteRookie
Member
Can a fluted AR bull barrel be turned down in profile with no ill effects? Just curious...
Can a fluted bull barrel.....
- Thread starter MnYoteRookie
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MnYoteRookie
Member
Quote:
I would imagine it can. Lots of light sporter barrels out there. The flutes aren't cut deep enough to effect barrel strength. Ask your smith that's going to do the barrel work.
Hi Bob...
This was just something I've been thinking about to reduce the weight on my 20" bull upper. It's just an idea at this point but if it can be done without drastically affecting performance, I may think a bit harder about the project.
Would any of our resident smiths care to offer an opinion?
I would imagine it can. Lots of light sporter barrels out there. The flutes aren't cut deep enough to effect barrel strength. Ask your smith that's going to do the barrel work.
Hi Bob...
This was just something I've been thinking about to reduce the weight on my 20" bull upper. It's just an idea at this point but if it can be done without drastically affecting performance, I may think a bit harder about the project.
Would any of our resident smiths care to offer an opinion?
speedkills
New member
I'd like to know one thing myself on this note with fluting! Lets talk basic thread-ology here.
Most machinists know that a thread is only as strong, as depth per diameter!
I'd like to know, how you determine max depth for a fluted barrel (For the flutes!) in relationship to bore? /ubbthreads/images/graemlins/confused1.gif
Most machinists know that a thread is only as strong, as depth per diameter!
I'd like to know, how you determine max depth for a fluted barrel (For the flutes!) in relationship to bore? /ubbthreads/images/graemlins/confused1.gif
IDBob
New member
Years ago I was building ultra-light rifles for sheep hunters in Alaska. I was using Rem 700 actions and turned some pretty light barrels. These lightened barreled actions were stuck in Brown Precision stocks. These were glued in with no stock bolts. Never used any kind of formula for barrel diameter, but common sense. These were built in 270 Win and 280 Rem not that you couldn't use something like the 7mm Rem mag also, but we lightened everything possible.
My gut says that a barrel turned down to the same diameter as the existing flutes already cut in a barrel is still going to have plenty of meat for a barrel. Some of the original M-16's had pencil thin barrels when they first came out. Of course for the AR platform you still have to have a gas port.
Threads on a bolt would appear to me a different situation than a barrel as there's a totally different kind of stress applied to a threaded bolt than a rifle barrel.
If you go over to Varmint Al's web page he's got a bunch of stress patterns on different barrels, but I don't know how that would apply here.
Here's a good smith to check with that probably would know a lot more than I would about barrel thickness's compared to cartridge pressures for any given cartridge.
http://www.cutrifle.com/
My gut says that a barrel turned down to the same diameter as the existing flutes already cut in a barrel is still going to have plenty of meat for a barrel. Some of the original M-16's had pencil thin barrels when they first came out. Of course for the AR platform you still have to have a gas port.
Threads on a bolt would appear to me a different situation than a barrel as there's a totally different kind of stress applied to a threaded bolt than a rifle barrel.
If you go over to Varmint Al's web page he's got a bunch of stress patterns on different barrels, but I don't know how that would apply here.
Here's a good smith to check with that probably would know a lot more than I would about barrel thickness's compared to cartridge pressures for any given cartridge.
http://www.cutrifle.com/
dtech
New member
A fluted barrel can be turned down. It's certainly not desirable, but it can be done.
Back about 10 years ago, one of my AR customers got into a 4-wheeler accident and really put the hurt to his AR. His insurance company settled with him, and he brought the gun to me to repair. The barrel ended up getting dragged on the pavement, and had a lot of damage on one side, mostly near the muzzle. I replaced the barrel, free-float tube, gas-block and several other parts, and sent it on it's way.
Later, I took that barrel and turned the diameter, from the gas-block to the muzzle, from .900" down to .860" and built it into an AR for my son. That barrel still shot fantastic! Now I may have just been lucky, but after all that barrel had been through, I didn't have anything to loose.
While barrel diameter VS. accuracy is purely a trade-off, fluting depth is mostly a safety issue. The heaviest barrel will generally be the most rigid, and the most accurate. On the AR platform, there are limitations to what degree of accuracy improvement that can be expected, beyond a certain diameter barrel.
The fluting depth should be dictated by several things: 1) barrel material. 2) bore diameter. 3) operating pressure of the cartridge. 4) the area of the barrel.
The larger the bore diameter, given the same pressure and barrel material, the thicker the barrel needs to be to have the same safety margin. This may not make sense to some of you, but it's true. The more AREA in the bore for the PRESSURE to act on, the more stress that same pressure will impart. Look at a propane cylinder: If you purchase a 1 pound cylinder from Wal-Mart, the tank material is just thin sheet-metal. Now if you get a 20 pound cylinder for your gas-grill, the material used is heavier than on the 1 pound tank. By the time you get into the 1000 gallon tanks, they are made out of very heavy plate. The propane that each of the tanks contain is the same, and generates the same pressure at the same ambient temperature, but as the area of the inside of the tank increases, the thickness of the tank material has to go up in proportion.
The area of the barrel that you are fluting is also important. Peak-pressure will normally be in the first few inches in front of the chamber. Fluting in this area would need to be quite shallow. The pressure out near the muzzle will normally be quite a bit lower, and fluting in that area can be more agressive. Fluting too deep near the muzzle can have an adverse effect on accuracy though. Deep fluting out near the muzzle can turn the muzzle area into a "tuning fork".
Back about 10 years ago, one of my AR customers got into a 4-wheeler accident and really put the hurt to his AR. His insurance company settled with him, and he brought the gun to me to repair. The barrel ended up getting dragged on the pavement, and had a lot of damage on one side, mostly near the muzzle. I replaced the barrel, free-float tube, gas-block and several other parts, and sent it on it's way.
Later, I took that barrel and turned the diameter, from the gas-block to the muzzle, from .900" down to .860" and built it into an AR for my son. That barrel still shot fantastic! Now I may have just been lucky, but after all that barrel had been through, I didn't have anything to loose.
While barrel diameter VS. accuracy is purely a trade-off, fluting depth is mostly a safety issue. The heaviest barrel will generally be the most rigid, and the most accurate. On the AR platform, there are limitations to what degree of accuracy improvement that can be expected, beyond a certain diameter barrel.
The fluting depth should be dictated by several things: 1) barrel material. 2) bore diameter. 3) operating pressure of the cartridge. 4) the area of the barrel.
The larger the bore diameter, given the same pressure and barrel material, the thicker the barrel needs to be to have the same safety margin. This may not make sense to some of you, but it's true. The more AREA in the bore for the PRESSURE to act on, the more stress that same pressure will impart. Look at a propane cylinder: If you purchase a 1 pound cylinder from Wal-Mart, the tank material is just thin sheet-metal. Now if you get a 20 pound cylinder for your gas-grill, the material used is heavier than on the 1 pound tank. By the time you get into the 1000 gallon tanks, they are made out of very heavy plate. The propane that each of the tanks contain is the same, and generates the same pressure at the same ambient temperature, but as the area of the inside of the tank increases, the thickness of the tank material has to go up in proportion.
The area of the barrel that you are fluting is also important. Peak-pressure will normally be in the first few inches in front of the chamber. Fluting in this area would need to be quite shallow. The pressure out near the muzzle will normally be quite a bit lower, and fluting in that area can be more agressive. Fluting too deep near the muzzle can have an adverse effect on accuracy though. Deep fluting out near the muzzle can turn the muzzle area into a "tuning fork".
PineCone
New member
MnYoteRookie
Member
WOW!!! Thanks Mike for the detailed response!! And to all who chimed in as well!!
Since this rifle is basically a "bench" gun and was not really built to carry all day, I probably just leave it be and think about a new, lighter weight upper. It shoots fairly well (sub MOA) and I'd hate to "fix" something that doesn't need fixing...
Having rolled the dice on a few projects like this and shot craps, I think I'll just play it safe this time.
Thanks again!!!
BTW... Is there such a thing as a light weight .204 upper? /ubbthreads/images/graemlins/confused1.gif
Since this rifle is basically a "bench" gun and was not really built to carry all day, I probably just leave it be and think about a new, lighter weight upper. It shoots fairly well (sub MOA) and I'd hate to "fix" something that doesn't need fixing...
Having rolled the dice on a few projects like this and shot craps, I think I'll just play it safe this time.
Thanks again!!!
BTW... Is there such a thing as a light weight .204 upper? /ubbthreads/images/graemlins/confused1.gif
dtech
New member
Quote:
WOW!!! BTW... Is there such a thing as a light weight .204 upper? /ubbthreads/images/graemlins/confused1.gif
You can build a light-weight .204 upper, but not as easy as some other calibers. Where the .223 Remington does quite well with a 20" barrel, I feel that 20" is too short for a .204. I have built them, and they shoot good, but they are very LOUD and you do loose some of the velocity potential.
The .20 cal. bore is enough smaller than a .224 bore that a slightly lighter contour than a standard "bull" contour can be used and still end up with a good rigid barrel. When you start getting into real light contours, then you end up playing the "trade-off" game with accuracy.
WOW!!! BTW... Is there such a thing as a light weight .204 upper? /ubbthreads/images/graemlins/confused1.gif
You can build a light-weight .204 upper, but not as easy as some other calibers. Where the .223 Remington does quite well with a 20" barrel, I feel that 20" is too short for a .204. I have built them, and they shoot good, but they are very LOUD and you do loose some of the velocity potential.
The .20 cal. bore is enough smaller than a .224 bore that a slightly lighter contour than a standard "bull" contour can be used and still end up with a good rigid barrel. When you start getting into real light contours, then you end up playing the "trade-off" game with accuracy.