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View Full Version : Barrel to barrel extension torque


raubvogel
September 18, 2017, 05:20
How much torque is applied when the two meet each other? Also, right handed threads, right?

hueyville
September 18, 2017, 07:13
150 ft/lbs for barrel extension, you do realize will have to cut extension or barrel shoulder to properly set headspace. The barrel/barrel extension are 16 TPI so one full revolution equals 0.0625" if my head is doing math correct. If barrel is already drilled for gas its generally easier to weld gas vent then redrill dead top center after get extension properly torqued and headspaced. If your good with a lathe can line up the extension and locating pin deal top center with gas port. Remember muzzle device is 10 to 20 ft/lbs and if someone over torque muzzle device in combination with aggressive thread lock or doesn't realize it's pinned, seen people unscrew barrel from extension if use receiver clamshell fixture in vice secure upper or use reaction rod to remove the muzzle device.

On way to Shepard Spinal Center for a nerve block, blew my stinking back out again. Think my lumbar fuse blows at about 10 ft/lbs now. Don't remember doing anything heavy yesterday but not slept all night and called the surgeons emergency number and said to get my @$$ to ATL, has a full book but can work me in.

hueyville
September 18, 2017, 07:32
It's been my experience that all you really need to harvest a deer is a car. They come right through the windshield just fine.

On your signature, my Dodge trucks drag deer under and then spit them out the rear in pieces after the differentials pull them apart. Usually requires a new bumper cover. Wife was wanting to buy a car due to issues getting in and out of her 3/4 ton 44 diesel. Asked our mechanic if he would put his wife in a car and said no. His wife drives a G 550 which he says is a steel box on 3/4 ton chassis. About two weeks later wife hit a big deer on interstate with cruise set at 78 mph. Realized had she been in a car would have died. In following year had three friends die hitting deer (one in small station wagon other two on motorcycles) then I whacked one as slowing to turn in driveway on one of my bikes. We went through period between wife and I hit five deer in 18 months. Last Easter had two run into side of my truck as pulled out of drive and another time turned in yard where five freaked out and began running in circles, one ran into side of truck I was driving, another ran into a parked truck while a third failed to see chain link fence and hit it at full run and piled up in yard. Been asking DNR and Army Corp of Engineers for some kind of permit to murder them year round and use neighbors backhoe to bury them. Our insurance agent says a vehicle strike of deer is reported on our road five days per week. Hate them things when go unchecked.

the gman
September 18, 2017, 09:45
How much torque is applied when the two meet each other? Also, right handed threads, right?

Barrel extension torque is generally accepted to be between 120 and 140ft/lbs. Some smiths go as low as 30ft/lbs, some go to 160ft/lbs but the consensus is somewhere between 120-140. Brownells go for good and tight:

http://www.brownells.com/.aspx/lid=16219/GunTechdetail/Brownells-Gunsmith-Corner-July-2013?avad=avant&aid=135323&cm_mmc=affiliate-_-Itwine-_-Avantlink-_-ale&utm_medium=affiliate&utm_source=Avantlink&utm_content=NA&utm_campaign=Itwine

You will need a barrel extension nut to install it properly and you have a choice of a few:

http://www.brownells.com/gunsmith-tools-supplies/rifle-tools/barrel-tools/ar-15-m16-barrel-extension-torque-tools-prod27452.aspx

http://www.brownells.com/gunsmith-tools-supplies/rifle-tools/wrenches/ar-15-barrel-extension-wrench-prod12729.aspx

There are others but I have the second ones, both in 5.56 and another in .308. The first one is cheaper and you can use it to support the barrel when installing the barrel nut and muzzle device. Barrel NUT per mil spec is between 30-80ft/lbs. Muzzle device is 15-20ft/lbs.

oleblu72
September 18, 2017, 11:04
On your signature, my Dodge trucks drag deer under and then spit them out the rear in pieces after the differentials pull them apart. Usually requires a new bumper cover. Wife was wanting to buy a car due to issues getting in and out of her 3/4 ton 44 diesel. Asked our mechanic if he would put his wife in a car and said no. His wife drives a G 550 which he says is a steel box on 3/4 ton chassis. About two weeks later wife hit a big deer on interstate with cruise set at 78 mph. Realized had she been in a car would have died. In following year had three friends die hitting deer (one in small station wagon other two on motorcycles) then I whacked one as slowing to turn in driveway on one of my bikes. We went through period between wife and I hit five deer in 18 months. Last Easter had two run into side of my truck as pulled out of drive and another time turned in yard where five freaked out and began running in circles, one ran into side of truck I was driving, another ran into a parked truck while a third failed to see chain link fence and hit it at full run and piled up in yard. Been asking DNR and Army Corp of Engineers for some kind of permit to murder them year round and use neighbors backhoe to bury them. Our insurance agent says a vehicle strike of deer is reported on our road five days per week. Hate them things when go unchecked.


I tagged a big ole buck one year with my dump truck. He came flying out of a corn field when he hit the road and saw me coming he tried to stop and his feet slid out from under him and that's all she wrote there wasn't any deer parts left to drag off the road the pieces were so small probably could have made deer sausage though.

Mark

hueyville
September 18, 2017, 21:26
Thanx Gman for the additional specification range. Been times before where replacing a barrel extension thought if could stop down in the 120 to 125 ft lb range would have been top dead center and good to go. I live by using calibrated wrenches and meters. Have a torque wrench rated to 2,000 ft lbs with calibrated 4:1 gear reduction wrench so technically can run up to 8,000 ft lbs though wrenches are usually not accurate at top or bottom end of their range. My little 0 to 3 inch pounds wrench with fractional inch/ounce resolution is cute as a bug. Have every size in between and on occasion company that calibrates my wrenches, meters and scopes will call and ask to borrow one. My two most rare and accurate wrenches am only local client they know with such in stock. Thanx Gman for the additional specification range.

Been times before where replacing a barrel extension thought if could stop down in the 120 to 125 ft lb range would have been top dead center and good to go. I live by using calibrated wrenches and meters in conjunction with good reference for most fasteners. Have a torque wrench rated to 2,000 ft lbs and calibrated 4:1 gear multiplier wrench so technically can run up to 8,000 ft lbs though even good wrenches are usually not accurate at top or bottom end of their range. My little 1 to 3 inch pounds with 1/10th ounce resolution is cute as a bug. Have every size in between and on occasion the company that calibrates my wrenches, meters and scopes will call and ask to borrow one of my torque wrenches, Fluke Earth Resistivity tester for testing ground rod bonds if get a Q.C. job and trade me several free calibrations. Say my insulated torque wrench made in Sheffield England is most accurate handheld torque wrench in its range have ever tested. Keep doubles and triples of everything so not doing without while something is in for calibration. Ma Bell requires putting serial number of every tool with calibration date less than year old even on battery terminals and logging on every line item of an invoice. The big wrench is used every five years for convenience store chain as had a sign fall and kill a person due to bolts not being torqued to proper value so they have all their big signs Q.C.'d every five years. Same with big monopole billboards, the occasional contract checking torque values is good extra income.

Have read the 150 ft lb as a static number from multiple sources but with your extensive experience in the industry and common sense application going to be willing and stop in the 120 range and go as high as 160 if real puts me top dead center on an extension replacement. Your experience in the industry trumps an arbitrary number I read.

raubvogel
September 24, 2017, 09:35
I must then be on the high range. I am using rata's calientes barrel vise (http://falfiles.com/forums/showthread.php?t=418989), with lead sheets to account for barrel differences, torqued to 30ft-lb. And it is still slipping.

the gman
September 24, 2017, 12:05
I must then be on the high range. I am using rata's calientes barrel vise (http://falfiles.com/forums/showthread.php?t=418989), with lead sheets to account for barrel differences, torqued to 30ft-lb. And it is still slipping.

Are you trying to torque an extension to match up to a pre-drilled gas port? If so, depending on if you have headspace gauges, you can either use some .001 shim stock or trim the shoulder on the barrel to get you where you need to be.

Use some powdered rosin (available from your nearest sports store) to stop the slipping in the Ratas vice with the lead shims. Or you can bore an appropriate sized hole through a 4x4 block and split it in half with a table saw then use the rosin and a big fcuking vise to hold that sucker together. I'd be tempted to stop at good and tight if it locked up at TDC as there really isn't that much rotational force on the extension once its locked in the receiver. Especially if you are going to drill a gas port rather than trying to match one up.

hueyville
October 15, 2017, 05:52
These torque values and other often asked build tips (as in same thread every two weeks for past two years) should be put in a sticky. Let mods add and remove posts to the build sticky based on whether actually contribute or not. If let this information get pushed off bottom of page questions answered will be asked again quickly.

the gman
October 15, 2017, 10:17
That would be a good idea. FYI, if you ever pull a barrel nut off a Ruger 556 AR, I can guarantee the torque on those bastards is well over 80ft/lbs.:(:(:(

Did one yesterday for a buddy and holy shit, that sucker was on there TIGHT! Took a 3 foot cheater pipe on my wrench to break it free. Noticeable differences on the Ruger AR556:

1.Barrel nut doesn't have conventional delta ring and spring; delta ring is plastic and threaded on to barrel nut. To remove handguards, unscrew delta ring to rear and separate the HG's.

2. Front sight block is lightened and skeletonized, has 2 lightly tensioned taper pins on the top of the barrel and removes pretty easily.

3. Flash hider resembles the Ruger AC556 and doesn't have any closed ports like an A2.