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1/25/2018 7:38:29 AM
Posted: 6/6/2003 2:01:37 PM EST
I finally received my Bushy M4 Dissipator barrel assembly today. I know that I need to use some lube (Never-Seez) on the barrel nut, but should I also spread some around the outside of the barrel nut, the part that goes inside the front of the upper receiver? Also, do you use lube on the flash-hider?
Thanks, Seth
Link Posted: 6/6/2003 6:37:54 PM EST
You just want to feather on a little bit of lube on the receiver threads, too much and it will leak all over when the barrel gets hot. You don't need to use any on the FS, but it wouldn't hurt.
Link Posted: 6/7/2003 2:59:57 PM EST
The purpose of the lube is to just allow smooth assembly and accurate torque reading. Never Sieze is not necessary, and it contains gritty metal solids, ground up aluminum, that is OK for use on steel studs and such on engine blocks, but not really useful for your aluminum receiver. I use ordinary moly wheel bearing grease (the type "for disc brakes"). Yes, use it sparingly. I recently removed the barrel from a receiver, and the flash hider, that I had assembled about 15 years ago. The grease was still on the threads, and the parts came off with no undue force.
Link Posted: 6/10/2003 6:45:33 PM EST
Would the fellow who contacted me about the post above please do so again. I accidently deleted the post before I could answer. I apologize. Thanks, A Free Man
Link Posted: 6/10/2003 7:01:44 PM EST
This was posted by A_Free_Man in another thread, and I think you'll find it very helpful.
When you plug the barrel into the upper receiver, which should be chucked up in your vise in an action block WITH the insert in place of the bolt carrier, there is a little slot at the top on the receiver. There is an indexing pin on the upper side of the barrel that engages that slot. Now, put some moly grease (ordinary wheel bearing grease) on the threads of the receiver and snug it up by hand. Do this several times to spread the grease. The purpose of the grease is to help give a true torque reading, not read the friction of the nut and receiver. To smooth the threads, using the barrel wrench and torque wrench, tighten the barrel nut to 30 ft-lb. This AIN'T rocket surgery, as my wife says. Back off, and tighten to 30 a second time. ---- edited to add: Back off again, then torque up the third and final time. ---- Before we tighten the last time, let me explain... the torque to tighten is simply an amount that will keep it from backing off by itself, and make sure everything is fully in contact, solid barrel to receiver mount. And also that the nut is not overtorqued, stripping the thread, which happens over about 80 ft-lb. There is no magical torque reading that will make the difference in a good running rifle and not so good. It has NOTHING to do with headspace. OK, now, this time tighten to 31 ft-lb. Look at the notch nearest the hole where the gas tube enters the upper. Will the gas tube pass through without touching the barrel nut? You can use a drill bit shank, or the gas tube itself. Stick it in through the notch and into the hole. Will it swing from side to side equally? If so, you are done. Do not back off, you were at 31 ft-lbs, the minimum, SO, budge it a little more. Now check. You want the gas tube to go through and not touch the nut on either side. The gas tube needs to be able to "float" slightly, and flex, to smoothly engage the gas key when the bolt carrier moves. Gas tube clearance should be easily obtained under the 80 ft-lb mark, and usually is done under 60. That is it, done.
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Link Posted: 6/12/2003 5:29:27 AM EST
Thank you for the neat info Zardoz
Link Posted: 6/12/2003 8:55:11 AM EST
I would like to add, though the manual says 31 ft-lb minimum, anything over 25 ft-lb is plenty. Once you reach this point, do not worry about the torque, just get alignment for the gas tube. Even with this, if the gas tube will pass thru, and is straight, even though there is not an exact equal amount of clearance on both sides, it is ok. Just as long as the gas tube is not touching one side of the notch when it is straight. One of the most important things is a good vise, sturdily mounted.
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