- January 15, 2018 at 3:33 pm #48725
I mentioned recently that I have finally succumbed to the AR-15. Not that I didn’t know how to build them (I can put a match rifle together with half my brain tied behind my back) but I’ve not actually made a barrel for one from a blank until recently. I was shocked at the simplicity of it. Not only did they make the rifle itself dirt simple to assemble, but fitting the barrel to the extension etc etc is absolutely Thag industries easy. Everything is contained in that barrel extension. I slammed one out for myself in about 3 hours from the time I pulled the blank from the rack and said “hmmm. I wonder how that will shoot” to having it mounted on the rifle stacking groups at 100 yards. It was so easy I almost blinked and missed it.
The threads on the barrel are .812-16 (which is dirt simple because 16TPI has a thread depth of .062 or 1/16 of an inch.) The threads are .625 long or 5/8″ (you could dam near do this with a tape measure) and there’s a 1/8″ undercut at the shoulder. The extension is screwed on and set with Loctite 271 Red (hurberdurberdur). No grey hair. No deep thought. No crazy tolerances. Screw it on and go.
The chamber gauge was another discovery. I noticed that my headspace gauge had a very pronounced extractor cut in it, and it turns out the leading edge of that mark is the headspace dimention for an AR-15 chamber. I cut to that line and was within .010 of headspace first rattle out of the box. A couple twists with the reamer by hand allowed the perfect clearance for the bolt head lugs. Unbelievable.
The gas block cut is the only critical thing on the barrel and it was easily rendered and a hurried profile busted onto the blank which was easily polished out with the barrel in the spinner on the belt sander. After that, the barrel was installed on the reciever, leveled in the vice, a 3/16 rod went down the barrel and the gas hole was drilled.
On went the gas block, and handgaurd, BCG, and charge handle, snap it on the lower, push in two pins, attach a scope and it prints 1MOA at 100 yards with 55 grain Blitzking over 26 grains of Varget.
Compared to building a precision Mauser or Remington 700, you could almost accidentally build one of these in your sleep! Crazy.
- January 16, 2018 at 2:04 pm #48731Rattlesnake CharlieParticipant
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Yeah, even I’ve been able to put them together.
- January 17, 2018 at 9:49 am #48756popperParticipant
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You don’t pin the extension?
- January 17, 2018 at 11:32 am #48757
Of course I did, but it was a simple matter of tapping it in place. Barely worth mentioning. Its only purpose is to clock the barrel to the receiver.
- January 17, 2018 at 2:16 pm #48759HarterParticipant
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Heck even I can assemble one and have results .
One note worth noting . Barrel quality , barrel quality , barrel quality ! Yes it makes a huge difference . A bare bones zero nothing base kit will get you 2.5″ , 1.5″ with a jacket it likes . Spend $200 more on a good barrel and the zero nothing rattle trap shoots like GSs .
- January 17, 2018 at 7:47 pm #48762kensParticipant
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I couldn’t understand the aluminum reciever of the AR15, understand how the thin aluminum could hold the bolt in tolerance nor take the recoil until; I saw one apart and saw the barrel extension.
It’s the barrel extension that makes the lock-up of the bolt; I guess the extension is actually the ‘receiver’ per-se.
But then, I saw the different uppers, like .338lapua, 50bmg, and other esoterica, and I couldnt understand, until, I realized the lower, which is the AR receiver, is really just the trigger group. (magazine well if needed)
Seeing the extension, bolt & barrel all 3 pieces in your hand made me realize how cute these things really are, but then, they are not blued steel and bright walnut. they are cute, but they are not ‘pretty’
- January 18, 2018 at 9:50 am #48771popperParticipant
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I figured you put the pin in but wondered why the red loctite? I’ve seen Utube where it is used to seat the extension in the receiver as well as receiver socket being ‘squared’ and true’d. Just curious.
- January 18, 2018 at 2:30 pm #48776
It’s just like anything else. You can torque the snot out of it and hope it doesn’t turn loose (while inducing internal stresses in the barrel) or you can apply red loctite and torque to about 30 Ft/Lb and let it ride. This is how the Army Marksmanship teams do it, and they are right.
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