Do you bed your barrel extention?

RT2506

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If you do bed what do you use? If you use locktite what number do you use?
 

eklarsen

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I think most folks use 648, I used 680 as it will fill a little more gap and is slightly more heat resistant

I just checked, 648 will fill up .007 gap whereas 680 will fill .015
 

MudRunner2005

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If you do bed what do you use? If you use locktite what number do you use?
I don't bed mine, but I do spread a thin layer of Loctite C5-A copper anti-seize on it, and on the barrel nut before installing them (wipe any excess inside and outside the receiver, of course), so things don't get stuck on there later if I ever choose to swap the barrel or have to do any maintenance.
 

RT2506

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I decided to bed with Blue Thread locker from Permatex from information I got from another site. I did my second build today. I used an Anderson upper with an Oden Works 223 W 18" DMR barrel with their tunable gas block and a STNGR float tube. Discovered that the gas block was hitting the tube on the inside and had to use a Dremal and file on the inside of the tube to make wiggle room. It is free floating now. This was my second build from scratch so it got me to thinking. I better check out my first build I did a couple months ago. It was a 6.5 Grendel but I used the same maker barrel and gas block and float tube and sure enough the gas block was hitting on the inside. I removed the tube and Dremaled it so there is wiggle room with it now. Lucky this was a intermediate length gas barrel because with my flex wand attachment on the Dremal I could just reach where I needed to grind on the tube. I had shot this rifle and with certain handloads it shot great, maybe it will shoot great with everything now that it has a truly free float barrel.
 

MudRunner2005

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Hey, just for terminology sake, the term "tube" is almost exclusively used with the gas tube and the buffer tube. The part over the barrel is referred to as the handguard.

The only reason I make that distinction, is because when someone not familiar with the nomenclature reads "I used a dremel on the tube to make wiggle-room", they might be thinking you're talking about the gas tube, and that could be HIGHLY dangerous to do, and someone could get hurt.
 

RT2506

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I am sorry for my ignorance of the "new" nomenclature of the parts of the AR platform. I was coming of age when the AR platform was being introduced to the world. That triangle plastic thing was called a forearm back then. When you got down tight in a sling you would actually torque that pencil of a barrel sideways causing all sorts of accuracy problems. As time moved forward someone decided that a heaver barrel was needed and that the heat shield under that plastic forearm and the delta ring at the back needed to go because of it's touching the barrel causing harmonics problems. Thus came about what was called the "free float tube" because it was just a metal tube attached to the barrel nut that touched nothing else. I keep forgetting that we live in a PC correct world these days and that the younger generation likes to change nomenclature of things. I am also sorry for what might be deemed carelessness for causing someone to mistake the gas tube for the "forearm". I keep forgetting that there is not much common sense in the younger generation that does not understand the workings of certain things and never gets the full story before jumping into things or never reads instructions. For example Tide pods instructions state that they are not supposed to be eaten and condoms are for other uses than snorting them up ones nose. Thanks for the information on nomenclature.
 

J E Custom

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I don't bed the barrel extension ether. Like MUD, I use anti seize and torque It down to recommended torque. I use a torque wrench and found that using Anti Seize reduces the amount of torque required to make up clean, dry threads. so after testing both dry and with Anti Seize the torque was reduced 15% using the Anti Seize to get to the same point.

I have never had one come apart and when rebarreling, removal is possible without damaging anything.

J E CUSTOM
 

tim_w

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Mar 25, 2008
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Bedding the reciever for the barrel extension does help if the fit it not tight. If you cam
N just slide a barrel with easy then it helps to bed. Ideally guys the better choice and what we moved to was tighter spec on the reciever or slightly oversized barrel extensions. The ideal fit after putting my share of high end ARs together is a fit where you heat the receiver or takes some work to get the barrel in. Not a serious press fit using a hydrualic ram or a sledge hammer but takes some real manual force. More of a tight slip fit. The bedding depending whatt you use can reduce frriction. I always useed somethung to lube it. Other thing I do to enure barrel nut tensions consistent putt some purple or plue locktite on the threads. Just a small amount. Then torque thee nut to the min tq spec andd brreak it lose 2-3x then to your final where you line up any holes etc as needed try to hit the middle upper range of spec but not max or over if it can be avoided.

The issue is unless you are covering all the other bases of building a match upper this effect unless its real sloppy can/willl get lost in the noise. Its like that last thing to get max precision shooting strings as the barrel reciever face etc heats up.

A barrel capable of at least 1/2 moa 5 shot groups at 100-200 yd.

Square the reciever face(end of the barrel extension port).clean it up the way you would skim turn a case neck. Just around 1/2-3/4 virgin alum showing. Do not take more than needed or it will effect extension match with internal front face i.e. end up with feed ramp lip/ step and pin notch depth issues. Make sure the pin iss not jammed to the reear of the notch.

There are a few other steps on the upper not to mention a tight fit lower and its setup i.e. trigger as well.

While ARs can be legos, if you really want to put one together with tight specs and ensuring proper timing , max efficiency of the gas system as well as reliablity there lots of small steps to fitting parts and using spec spec parts than just using parts kits. Case in point I would never use a complete bcg. Alway build your own bcg make sure parts fit properly, ejector extractor and the springs you use for them etc.... lots of extra steps that gives you the diff between a loose gassy oem and a tight fitting yet still runs like a sewing machine and has better reliability. Its lots of little things that together can make a noticabble difference-compared too just following SOP with generiic parts.

One thing I did and later had my kids do for me was lubing up and hand cycling the upper on a shop lower 500 cycles before cleanup, test firing, final inspection, and boxing. It goes from gritty to silky smooth and the bolt will lock fully closed even if you just rested it as it engaged the extension from the welll worn buffer spring, All the engaging parts get lapped/mated to each other nice and smooth. Doing this and you do not need to over gas the upper which is done as SOP to reduce tech calls from customers that some how forgot machines need to be broken in. But instead expect low pressure, steel case wolf ammo, to cycle perfectLY from round one and be lucky if they bothered to wipe it down and lube it.

(BTW I can not say 100% but the info on using the pertex blue paste threadlocker likely came from me. We use to keep most all the accuracizing info very close to the vest yrs ago. But I overtime had told a few people about using the paste which I was using before changing to a differnt product and finally to using specific tighter tolerance parts. JP was doing that before he started his own recievers. You can also use shim.).
 
Last edited:

357Max

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Jan 27, 2019
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Old thread, but good question.

If extension is a tight fit I would just use a little graphite anti seize.

The last one I built using quality parts had a very loose barrel extension to upper fit (VLTOR upper - Faxon barrel).
I used Loctite 620 with loctite SF7649 primer combined with .001 SS shim stock wrapped about 120 degrees around top side of extension.
The 620 is high temp up to 450 deg. F vs. 300 deg for the 648 & 680.
The 620 fills up to a .015 void like the 680.
 
Last edited:

Deviant

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Nebraska
I don't bed the barrel extension ether. Like MUD, I use anti seize and torque It down to recommended torque. I use a torque wrench and found that using Anti Seize reduces the amount of torque required to make up clean, dry threads. so after testing both dry and with Anti Seize the torque was reduced 15% using the Anti Seize to get to the same point.

I have never had one come apart and when rebarreling, removal is possible without damaging anything.

J E CUSTOM
Plus 1 here. I used to use blue loctite but its a PIA if you want to remove the barrel later. Anti seize and proper torque works just fine unless you have a loose fitting extension.
 

5.56×250

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If the barrel will wiggle when seated , I use green loctite gap filler. If it's a forced fit, there is no need. It's not compllicated....if it's got play, it will shift when heat gets to it and the metal expands, complicated by the aluminum to steel interface between the barrel and upper.
 

5.56×250

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It is a PIA if you have to remove the barrel, but its doable and worth the hassle IMO, if accuracy is your goal. I use a 1/2" extension and a socket that fits the diameter of the barrel extension. I slide it in the rear of the upper and tap the barrel out while holding the upper /lower in a vise with the clip insert type block. I glue a thin piece of rubber to the face of the socket for a little protection against damage to the barrel extension as well. You have to pull the buffer spring/tube, but that's easy enough to do. Heating the area with a hair drier till it will burn you to the touch seems to help with removal too.
 

B23

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Oct 30, 2008
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Just put a Proof Research barrel in 6.5CM on my Seekins SP10 and it fit like a glove.

I'm a big fan of using ARP Ultra-Torque assembly lube on the threads, particularly when screwing steel threads into aluminum threads. I've been using the same tube of ARP assembly lube for years, it's an excellent product.
 

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