Installing a new AR barrel

[chp5]

OK, I want to try a new barrel in one of my AR's. I have the DPMS multi-tool, but I don't have a torque wrench or a vice block-thingy to hold the receiver while installing the barrel.

Do I really need the torque wrench?

Can't I use an old mag in a vice to hold the receiver?

. . . or should I just give it up and send it to a smith?

Thanks.

[rhino]

I would get the vise block for sure. It's not that expensive and you'll avoid unhappy results that way.

[stingerjg]

DO NOT under any circumstaces try to remove the barrel nut by clamping the lower reciever. Unless you want to buy a new lower and upper reciever. It gets ugly fast. You must use a AR-15/M16 RECEIVER ACTION BLOCK to do the job without damage.

as far as the torque wrench is concerned, I have never used one. That dosent make it correct. but I have never needed one. The Mil spec of 30ft/lbs is just so the barrel nut does not fall off. I usally go hand tight and then use the wrench to go to the next hole.

Check out the military service manual for more info. TM 9-1005-319-23 page 3-40

PM me if you need more info.

[Mig]

Cy,

Don't try this without the upper receiver block. Talk with Bear1142 - he has the receiver block and could help you out.

Mig

[kurtm]

Wow you guys are to fancy for me! I usually clamp the barrel in a vice with barrel blocks ( aluminum plates with a vee cut in them ) and use the multi tool. Blue lock-tite the extention ( where it goes into the reciever) go hand tight and then wrench to the next notch that lines up. DO NOT lock-tite the threads!!! KURTM

[chp5]

Thanks for the replies guys. I'll give it a try.

[Patrick Sweeney]

Loctite? Oh, dear god, please tell us you didn't. Done right, you need loctite in exactly (let me see now, carry the one, add a decimal place) no place on an AR.

Get either the barrel blocks or an upper receiver block. Get a good barrel nut wrench, not one of the old mil-spec "three pin" plates.

Check, and if needed, adjust headspace before you install the barrel. It is so much easier than doing it once the barrel is in place.

Clamp either your barrel or the receiver. Slide the barrel in, and hand-spin the nut on. Take the wrench and tighten and loosen the nut twice. You want to rub off any high spots, wire edges grit, etc. Then tighten the nut with the wrench until a notch in the nut lines up perfectly with the gas tube hole. You will go 'way past 30 ft/lbs. If it is not physically possible to tighten to a notch you have to disasemble and figure out where you need to remove metal. (The advanced course of barrel install.)

then install gas tube, handguards, etc. Be sure your gas tube does not rub on the carrier key whent he carrier slides home without a bolt in place. Binding is bad, leading to premature gas tube tip wear. If it binds you'll have to carefully bend it until it slides home without binding or rubbing.

[kurtm]

Pat:

I have found that "Blue" around the extention, helps to stop "zero drift" when the gun is bounced around on a bi-pod. No matter how tight you crank the nut on, there will always be some radial slop. Yea it isn't much but I have seen it drift a minute around in a cicle over the course of a year. I am not alone on this idea, and several Barrel makers use this proccess when rebarreling NM ARs. I have even been known to use Accra-Gel to get the wiggle out. Oh yea and one othere place for "Blue" is the butt stock screw. I watched one guy loose his stock durring a match, He finished, but without a BUTT . He was just lucky that the rear reciever pin didn't drift out! KURTM

[Pact-Man]

How would one adjust headspace during this process?

[Patrick Sweeney]

Hmmm, glue the barrel in place to cure a zero-drift problem, and create a potential "heat it to remove it" problem. Glad I don't do much 600 yard NRA High Power. (the next book may change that, however.)

Headspace is adjusted by reaming a too-short chamber until the bolt will close on a "Go" gauge. If your barrel (new) is chrome-lined you aren't going to be reaming it, and should buy a new bolt with the barrel, headspaced by the manufacturer. Check headspace with extractor and ejector removed, and chamber scrubbed clean.

[JTAC Supply]

Very unlikely that your headspace won't be in spec with a new barrel and bolt, but it can happen. Always a good idea to check and make sure. Ditto the above, a torque wrench isn't absolutely necessary, but the vise block pretty much is. You can do it with barrel vise jaws, but the receiver block works better and can prevent bending the alignment pin and getting an off center front sight.

Jason