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Posted: 8/21/2014 10:28:53 PM EDT
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Would sure like to see someone take the time to explain fitting a barrel extension to the receiver for accuracy.
I know a good snug fit is desirable but what if it is either too tight or too loose? Appreciate it.. |
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Google?
Also i think there is an upper build guide somewhere on these forums: |
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we are here to help, but you have to look around some too.... At the top of this section there are links to huge tutorial threads like this one, http://www.ar15.com/forums/t_3_4/226782_Assemble_your_own_LOWER__UPPER__FREE_FLOAT__TRIGGER__GAS_BLOCK___Step_by_step_instructions_.html this link has all the instructions in it. |
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For accuracy lap the upper first. Once that is done install the barrel and use the minimal torque needed over 30 ft/lbs This is easier with proprietary HG nuts that do not require positioning for the gas tube/drive rod. The stuff by Diamondhead is a good example of this, just torque to 30 and done.
Some will add loctite between the extension and the inside of the upper but I see this as unnecessary. The interface of the upper meeting the flange of the extension are what matter, and minimal torque = minimal distortion. |
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I'm a loctiter. Why? Because the barrel can walk in a circle in the upper under the pressure of the rifling spin. If you didn't hammer the barrel into the upper, loctite is warranted
I generally torque to 45 ft/lbs. Quoted:
For accuracy lap the upper first. Once that is done install the barrel and use the minimal torque needed over 30 ft/lbs This is easier with proprietary HG nuts that do not require positioning for the gas tube/drive rod. The stuff by Diamondhead is a good example of this, just torque to 30 and done. Some will add loctite between the extension and the inside of the upper but I see this as unnecessary. The interface of the upper meeting the flange of the extension are what matter, and minimal torque = minimal distortion. |
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Quoted:
I'm a loctiter. Why? Because the barrel can walk in a circle in the upper under the pressure of the rifling spin. If you didn't hammer the barrel into the upper, loctite is warranted I generally torque to 45 ft/lbs. Quoted:
I'm a loctiter. Why? Because the barrel can walk in a circle in the upper under the pressure of the rifling spin. If you didn't hammer the barrel into the upper, loctite is warranted I generally torque to 45 ft/lbs. Quoted:
For accuracy lap the upper first. Once that is done install the barrel and use the minimal torque needed over 30 ft/lbs This is easier with proprietary HG nuts that do not require positioning for the gas tube/drive rod. The stuff by Diamondhead is a good example of this, just torque to 30 and done. Some will add loctite between the extension and the inside of the upper but I see this as unnecessary. The interface of the upper meeting the flange of the extension are what matter, and minimal torque = minimal distortion. This is BS. Amazing theory that will never manifest itself. Do you have any idea what the clamping load is between the barrel extension flange and the receiver torqued to 80 lb-ft? Go figure it out. There is no way the barrel is going to move relative to the receiver while firing. |
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Quoted: I'm a loctiter. Why? Because the barrel can walk in a circle in the upper under the pressure of the rifling spin. If you didn't hammer the barrel into the upper, loctite is warranted I generally torque to 45 ft/lbs. Quoted: I'm a loctiter. Why? Because the barrel can walk in a circle in the upper under the pressure of the rifling spin. If you didn't hammer the barrel into the upper, loctite is warranted I generally torque to 45 ft/lbs. Quoted: For accuracy lap the upper first. Once that is done install the barrel and use the minimal torque needed over 30 ft/lbs This is easier with proprietary HG nuts that do not require positioning for the gas tube/drive rod. The stuff by Diamondhead is a good example of this, just torque to 30 and done. Some will add loctite between the extension and the inside of the upper but I see this as unnecessary. The interface of the upper meeting the flange of the extension are what matter, and minimal torque = minimal distortion. |
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Quoted:
I'm not aware of any situation where loctite has been recommended for barrel installation... Quoted:
Quoted:
I'm a loctiter. Why? Because the barrel can walk in a circle in the upper under the pressure of the rifling spin. If you didn't hammer the barrel into the upper, loctite is warranted I generally torque to 45 ft/lbs. Quoted:
For accuracy lap the upper first. Once that is done install the barrel and use the minimal torque needed over 30 ft/lbs This is easier with proprietary HG nuts that do not require positioning for the gas tube/drive rod. The stuff by Diamondhead is a good example of this, just torque to 30 and done. Some will add loctite between the extension and the inside of the upper but I see this as unnecessary. The interface of the upper meeting the flange of the extension are what matter, and minimal torque = minimal distortion. And you ever try to remove a barrel that was locktited at the extension, I have and it was an extreme bitch. |
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Quoted:
I'm a loctiter. Why? Because the barrel can walk in a circle in the upper under the pressure of the rifling spin. If you didn't hammer the barrel into the upper, loctite is warranted What????? Seriously????? I have never heard of a barrel "walking in a circle" under pressure of the rifling spin. 
Are you saying the FSB can rotate while shooting? What about the locator pin in the barrel extension? |
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Quoted:
What????? Seriously????? I have never heard of a barrel "walking in a circle" under pressure of the rifling spin.
Are you saying the FSB can rotate while shooting? What about the locator pin in the barrel extension? Quoted:
Quoted:
I'm a loctiter. Why? Because the barrel can walk in a circle in the upper under the pressure of the rifling spin. If you didn't hammer the barrel into the upper, loctite is warranted What????? Seriously????? I have never heard of a barrel "walking in a circle" under pressure of the rifling spin.
Are you saying the FSB can rotate while shooting? What about the locator pin in the barrel extension? This, plus the clamping force that others have mentioned. Effing '04ers... eta... I've read reasons why people like to put loctite on the barrel extension, but NONE cited "barrel rotation" as a reason. Torque it and shoot it. |
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cmc201; You are missing something..."fitting a barrel extension to the receiver". It fits into the receiver one of three ways (1) Too Loose (2) Snugly (3) Too Tight.
(1) Snugly is most probably "Good". 
(2) Too Loose is probably "Bad" 
(3) Too Tight, I would think a pass with fine emery cloth to make it "Good". 
Someone will know the proper fitting if the two parts for accuracy from experience, I'm sure. |
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Quoted:
I'm a loctiter. Why? Because the barrel can walk in a circle in the upper under the pressure of the rifling spin. If you didn't hammer the barrel into the upper, loctite is warranted I generally torque to 45 ft/lbs. Quoted:
I'm a loctiter. Why? Because the barrel can walk in a circle in the upper under the pressure of the rifling spin. If you didn't hammer the barrel into the upper, loctite is warranted I generally torque to 45 ft/lbs. Quoted:
For accuracy lap the upper first. Once that is done install the barrel and use the minimal torque needed over 30 ft/lbs This is easier with proprietary HG nuts that do not require positioning for the gas tube/drive rod. The stuff by Diamondhead is a good example of this, just torque to 30 and done. Some will add loctite between the extension and the inside of the upper but I see this as unnecessary. The interface of the upper meeting the flange of the extension are what matter, and minimal torque = minimal distortion. How did you ever come to this conclusion ? 
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Quoted: The NDA I have covers the methodology. Sorry. If you are an engineer who works in aerospace you can probably figure it out. The best outcome is to have an upper and extension that are hammer and heat fit and exactly square. |
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Do you have access to EBSCO, the computer database that some universities have access to? You can search periodicals for American Gunsmith and get some of the articles written by Joe Carlos. He was the armorer for the USAR shooting team that are a very interesting read about fitting up barrels and chambering target rifles. There are also some videos you can watch on youtube. One of his articles discusses using BAT Machine Co. oversized precision barrel extensions and or .001 shim stock to get the extension into an interference fit. I think there is something to have the thing solid.
B [youtube] https://www.youtube.com/watch?v=pJL-IscH_jo&feature=player_detailpage&list=UUEDrqXDPSbQokSykVdPJT-Q [/youtube] |
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Quoted:
we are here to help, but you have to look around some too.... At the top of this section there are links to huge tutorial threads like this one, http://www.ar15.com/forums/t_3_4/226782_Assemble_your_own_LOWER__UPPER__FREE_FLOAT__TRIGGER__GAS_BLOCK___Step_by_step_instructions_.html this link has all the instructions in it. Well sir, after never having a hit on the SEARCH feature I finally contacted an administrator to inquire. It seems apparently the non-team members are not given access to the feature. I am a "Non-Team Member". I am now among the enlightened... Thanks for the assist 
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Quoted: I'm a loctiter. Why? Because the barrel can walk in a circle in the upper under the pressure of the rifling spin. If the barrel walked in a circle that was not press fit or loctite in place, wouldn't bolts in every AR that isn't setup like this be jamming left and right? Since the lugs of the bolt would not be able to follow the barrel extension's lugs as the barrel walked. What about the barrel's index pin that sits within the notch of the upper receiver? Why doesn't this do anything to counter this phenomenon? Also, barrels with front sight bases; if the barrels walked in circles, zeroes would never hold due to the front sight base rotating. I can care less about the dick measuring that happens on ARFCOM; but without an explanation on how this is specifically occurring, I cannot see this being plausible. |
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