If you have some bee's wax around the house, roll a little shaving into a mouse turd shape. Run a jag into the barrel and looking down through the gas port, line the jag up so that the solid part is right below the gas port. Push the wax plug into the gas port so that it runs into the jag and stops going in any further. Mash it down hard so that it expands to plug the gas port tightly. Remove the jag. Loctite the block in place and once you're satisfied that the Loctite has cured thoroughly, warm the gas block with a heat gun. The wax plug will fall through into the bore. Push it out with a patch. Blow some compressed air down the gas tube from the receiver end to displace any remaining wax and follow it up with some brake cleaner to wash any remaining wax off the surface of the port. Clean the bore as you normally would and you're all set. If, for some reason, there is any remaining wax, the first shot down the barrel will vaporize it. You can also use modeling clay, though it may not fall free when you heat the block. The jet of compressed air while the block is still hot, will displace it.
Hoot
EDIT: I forgot to mention to block the hole in the block that lines up over the port as well. Same method.
Hoot: I think he's talking about using the Green Loctite so he doesn't have to take off the gas block since he's never done it before.
BjornF16: I've never used the green Loctite but I wouldn't think enough would wick in to cause any problem getting into the gas port. The gas port is usually closer to one end of the gas block than the other so if you're really concerned, you could just do the side farther away from the gas port and see if that helps.
On the ones I've done, the barrel( AA barrels from Satern) has a dimple drilled in the bottom to index where the screw lines up to hold the gas block in place.
So it's pretty easy to line up the gas block by taking out the screw that will line up with that dimple and looking in the empty screw hole until it's lined up with the dimple.
Then I put a little Loctite 243 on the threads for the set screw and screw it in. That way it won't back out and I know I've got it lined up in the right spot.
This is using a low profile gas block with two set screws on the bottom.
I actually Loctite and install the second screw first with the other screw out so I can line up the dimple and then I Loctite and install the set screw where the dimple is.
When you see a barrel and gas block uninstalled you realize how easy it is but when you've never done it you might get worried about messing it up.
Your Satern barrel should have the dimple drilled into it and if you want to make sure just unscrew the screw closest to the upper receiver and look in the screw hole and you should be able to see the dimple.
Good luck.
Lee
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Here is a link to an excellent article on what makes an AR-15 accurate. http://bulletin.accurateshooter.com/2011...s-answers/
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I assembled it from scratch...there is a dimple present.
I'm leaning towards buying a rifle lenth MK-10 handguard and a low profile, adjustable gas block to replace the mid-length MK-10 and railed JPE adjustable gas block that I previously installed (these may show up on the trading post area soon). When I replace, I'll use the blue loctite. Turns out the green loctite requires heat to loosen.
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My goodness, that's one heck of a brake on there! Reminds me of my old CETME. 
Hoot
BjornF16: I know PRI makes an adjustable low profile gas block that looks just like the non-adjustable one AA sells and it looks not quite as wide as the one in the picture.
I think Satern was dimpling them to match the PRI gas block since that is what AA was using. At least the dimple matched the location of the set screw hole perfectly on the ones I installed. I just wish AA would also offer the adjustable PRI lo-pro gas block.
Yeah I thought the green Loctite was a more permanent version so I've never used it.
Good luck.
Lee
BjornF16: Is that a WCI brake you show in the picture? It sure looks like one if iit isn't.
Thanks.
Lee
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That is a Titanium Warped Industries (WCI)...awesome brake! (ordered direct from Warped to get the Titanium).
I was planning on getting the PRI adjustable gas block...I think someone had recommended that after I had ordered the JP Enterprises block. Now I have a reason to order the PRI! 
rasp65 Wrote:Here is a link to an excellent article on what makes an AR-15 accurate. http://bulletin.accurateshooter.com/2011...s-answers/ I respect Mr Whitley, but I don't agree with what he has to say in this article. I've built several uppers that will group tighter than his pictures without rigid receivers, or facing receivers and with flash hiders, and so on. It just isn't as complicated as he makes it out to be. But I can understand why he would like you think it is. My shooting partner shoots one of his match uppers in 6mmAR, it is a good upper, but it won't outshoot one I built for 70% of the cost.
Get a good barrel, that, I agree with.
Bob
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Quote:
Use anti-seize on the treads for the barrel nut and green (wicking) locktite on the gas block after it is mounted in place.
Bob,
Can you expand upon your technique of applying green loctite?
Do you feel the gas block is the most important component to bed with loctite to reduce/eliminate the vertical grouping?
HI, first let me explain why I use green locktite to begin with. I shoot service rifles a lot, A2's and A3's which have a front sight tower and gas block combination. It is important to get the front sight tower perfectly plumb so that the rear sight has equal windage adjustment left and right of the no wind zero. Quality service rifle uppers have set screws that rotate the tower by pushing on flats milled into the barrel. You begin by adjusting the tower left and right until you have a no wind zero at 200 yards with the rear sight centered and then use the green loctite to bed the gas block to the barrel and also to set the set screws so no further movement is possible. You can use gravity but it really isn't necessary as the loctite will be drawn into any voids or gaps due to capillary action.
After achieving the no wind zero, I usually clamp the upper in a vise and apply a bead of the green loctite to the barrel to gas block interface, and the set screws, allow it to wick into the gaps and then wipe any excess away with an absorbent cloth. I should have mentioned that I cleaned the barrel tenon, gas block bore and set screws with alcohol before assembly or adjustment. Once the loctite has set up, about 8 hours I then apply a protective layer to prevent corrosion, CLP or similar.
When I was at the NRA school of gunsmithing, some of the students used blue loctite on the barrel nut threads, but for reasons I never got to the bottom of they had to remove the barrels on some of them which required a torch and much outgassing. I saw no advantage to this compared to anti seize which came apart easily if needed.
We went to the NRA Whittington center and shot all the uppers we built at ranges up to 1,000 yards. The uppers built with loctite on the threads all shot worse than those with anti seize but I wouldn't attribute too much science to that as their were barrel quality issues mixed in with the results.
We took a lot of time examining all the barrels with a Hawkeye bore scope hooked up to a big screen TV so everyone could see the issues. After examining a few dozen barrels it doesn't take a rocket scientist to migrate from Shaw's to Kreiger's.
My personal belief is that a lot of hocus pocus is used to explain away poor performance from poorer quality barrels.
I'm on my fourth Kreiger barrel on my service rifle now and all of them have delivered less than .5 MOA with vanilla flavored upper receivers without tuning loads for them.
So to fully answer your questions, I think bedding the gas block is important, not always but in some instances where bad harmonics play. I don't think squaring the receiver face or tight fitting barrel extensions are important. It is important to use enough toque to get the barrel nut firmly engaged, and do so by backing off and retightening a couple of times. And I do think it is important to make sure the gas tube is centered and not rubbing on one side or the other of the passage way through the reciever.
Bob
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Great explanation. A couple of follow ups:
1. You don't apply loctite to the barrel extension that slips inside upper receiver? (anti-seize only on the barrel nut threads).
2. Any difference in accuracy between clamp-on gas blocks and set screw gas blocks (as alluded by Whitley)?
Thanks,
No, Loctite is not needed assuming a normal fit.
I don't see any evidence that a set screw attached gas block is detrimental to accuracy. I understand the theory, but in the real world it doesn't pan out that way. The Army Marksmansip Unit has the resources for serious testing and they use set screw attached gas blocks and routinely trounce civilians shooting match rifles with clamp on gas blocks. Troy Lawton is the chief component acquisition guy for the AMU and holds several national records himself. To qualify a new lot of components he sets up ten uppers and fires 20 shots from each in machine rail that clamps the uppers by the float tube. The requirement is that all 200 shots be placed in a 3" group at 300 yards. That's only 1 MOA but at 200 shots it is tough to do.
Bob
200-shot 1-MOA groups? As Ben Franklin once said, "Wow!"
I'd take that any day over the occasional .25MOA three-shot group.
I wonder what nuances with the AR15 the Grendel exacerbates that depart enough from 5.56 gun characteristics to where some of the tried and true accurizing techniques on 5.56 guns may be different with the Grendel.
That said, if you start with a Krieger barrel, you probably won't have many accuracy issues.
When testing barrel after barrel, day after day for a manufacturer, I gained a first-hand respect for Krieger barrels that told me they are not just a name. A lot of them shot .5 MOA groups right off the bat, with many shooting 1/3 MOA or better. One in particular impressed me so much, as it was a hummer, that I wanted to keep the rifle badly, but it was specifically ordered by a customer. It was one of those moments where I felt like the barrel was meant for me personally, but couldn't have it. That's the type of accuracy I chase, but rarely ever see.
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