Longevity, Accuracy Tips for the AR15

[babaganoush]

Just one works very well. I use the 220 lapping compound that came with my ring lapping kit. So, correct. You're not polishing.

The only steps needed to lap your upper:

Lap with compound
Stop soon
Wipe & check for 100% contact
Repeat as needed.

[45r]

I've read that some smiths put a little aeroshell 33MS on the threads and tighten down hand tight.

Then tighten down 3 times to next hole and sometimes don't even use a torch wrench.

Don't know if it's a good idea but some say 30 pounds is all that's needed.

The 33MS works good for lubing the lapping tool inside the receiver if you have a tight fit when squaring the receiver.

It's a high quality grease with 5 percent moly.

[cbe1962]

Aeroshell 33ms is also graphite-free. Based on research I did for my build, graphite is the chemical element LRRPF52 refers to in post #30 that reacts with aluminum and it is a component of most moly lubes. Aeroshell 33ms was the only graphite-free grease I found commercially available that meets the mil-spec for barrel nut grease. I bought a 14 oz tube for my builds, and have provided a handfull of the Horde with enough for a few builds out of my surplus. Search "Aeroshell" for more details if you are interested.

[LRRPF52]

I've mentioned it some other threads, but I wanted to share it here as well. As I have been truing uppers in preparation for the Lilja barrels, someone asked me to check their AA upper I have.

It was literally the only one that is dead-on true, not making it up. I didn't even think to check it earlier because of all the irons I have in the fire, so I was pleasantly surprised to see that not only was it perfectly true, but that it was anodized after being trued. It also was trued as part of the normal machining process, because there are no telltale signs of a lapping job. On top of that, the extension tunnel is very tight with several of the barrels I checked on it.

If all the AR15 uppers were made to AA's forged upper standards, there would be no need for this lapping tool.

If I were to put a retail value on an AA forged upper, it would be somewhere between $160 and $200.

[montana]

I've mentioned it some other threads, but I wanted to share it here as well. As I have been truing uppers in preparation for the Lilja barrels, someone asked me to check their AA upper I have.

It was literally the only one that is dead-on true, not making it up. I didn't even think to check it earlier because of all the irons I have in the fire, so I was pleasantly surprised to see that not only was it perfectly true, but that it was anodized after being trued. It also was trued as part of the normal machining process, because there are no telltale signs of a lapping job. On top of that, the extension tunnel is very tight with several of the barrels I checked on it.

If all the AR15 uppers were made to AA's forged upper standards, there would be no need for this lapping tool.

If I were to put a retail value on an AA forged upper, it would be somewhere between $160 and $200.

I agree, I have built many AR rifles using AA upper receivers. I have not had any slop in the inside upper receiver tube when fitting my barrels. They have also fit many different types of lower receivers that I have acquired with out any problems. I have had to blend the M-4 cuts to a few barrels but this is normal. They are top quality especially for the price when available.

[explorecaves]

I've mentioned it some other threads, but I wanted to share it here as well. As I have been truing uppers in preparation for the Lilja barrels, someone asked me to check their AA upper I have.

It was literally the only one that is dead-on true, not making it up. I didn't even think to check it earlier because of all the irons I have in the fire, so I was pleasantly surprised to see that not only was it perfectly true, but that it was anodized after being trued. It also was trued as part of the normal machining process, because there are no telltale signs of a lapping job. On top of that, the extension tunnel is very tight with several of the barrels I checked on it.

If all the AR15 uppers were made to AA's forged upper standards, there would be no need for this lapping tool.

If I were to put a retail value on an AA forged upper, it would be somewhere between $160 and $200.

Just got my tool in the mail today and checked the 3 Aero Precision blemished uppers I have on hand. Pleasantly surprised to find zero gap to be corrected. I will say the coating appears to be a little thick on 2 of the uppers in the interior where the BCG goes (rear of the ejection port) as I had to use the drill to rotate the tool to get it fully seated inside the upper (even with copious lube). The third slid in almost too easy for my likes, but I had already reserved it for my wife's .223 build due to a little play between the upper and lower (there is so little that she won't notice) so I am not too concerned about it being too loose for the barrel extension.

[LRRPF52]

Yeah, I just checked an Aero that I am using for another forum member's upper, and it is almost dead-on. Spin the upper on the tool with a bright light in the background and look carefully at the edges. You can see then if it is out or not, or just use Dykem fluid on the receiver face, let it dry, then skim the face with the tool in a drill and see what happens.

[explorecaves]

Yeah, I just checked an Aero that I am using for another forum member's upper, and it is almost dead-on. Spin the upper on the tool with a bright light in the background and look carefully at the edges. You can see then if it is out or not, or just use Dykem fluid on the receiver face, let it dry, then skim the face with the tool in a drill and see what happens.

Did this and couldn't see any light around the edges. I am used to using this method with my optics assembly background so I have a keen eye for any gaps. I will double check them again when I get ready to mount the barrel.

[45r]

Has anybody used a DPMS lo pro upper and needed to have it squared.

They are thicker and can be milled for a side charge later on if you want.

In an article by Robert Whitley it says it's good to use a thick receiver and you can bed the barrel to receiver with loc tite if the fit is loose.

I've read some say don't use loc tite,but he shoots very accurate ragged hole groups.

[customcutter]

Probably suggests using thicker uppers, so that there is less flex in the upper. Just an EWAG. That's why many use the billet uppers, which is what I bought for my Liberty barrel build.

Edit:

I plan on trying it without the loc tite. If I don't like the results, it's easy to go back and loc tite it. Just a suggestion.

[NugginFutz]

Has anybody used a DPMS lo pro upper and needed to have it squared.

They are thicker and can be milled for a side charge later on if you want.

In an article by Robert Whitley it says it's good to use a thick receiver and you can bed the barrel to receiver with loc tite if the fit is loose.

I've read some say don't use loc tite,but he shoots very accurate ragged hole groups.

My DPMS slick side was only slightly out of square, but I lapped it anyway, since I already had her in the stirrups, so to speak.

It also happens to be one of my straightest shooters, so I am pretty convinced the extra wall thickness has something to do with it. It also has a 24" SS Bull barrel, so the two seem to mate up well.

[LRRPF52]

For heavier barrels with bull profiles, it makes a lot of sense to use a billet upper with more beef to it. The VLTOR MUR is a great upper, as are the ones mentioned like Seekins, JP, Mega, and Precision Firearms.

If you are about to order your Grendel bolt from Precision, seriously consider using one of his billet receiver sets. They are actually Mark's own design, with some really nice touches in terms of funneling to the magwell, mate-up, and aesthetics. He also is a big supporter of this cartridge with both rifles and ammunition, and makes extremely accurate guns as those of you who own them can attest.

If you have the opportunity to buy an AA upper receiver, they are already trued and anodized, with a tight extension tunnel. There's a 16" AA carbine for sale here on the Forum as we speak.

Blue Loc-tite is one common method of bedding the extension to a somewhat loose tunnel, after you have trued the receiver face. Just keep the Loc-tite off the threads after you apply it to the OD of the extension, and clean up well. Heat from a heat gun on low is all you need to remove it at a later date.

Another thing I do with uppers that tend to be loose is Cerakote the inside, then lap the carrier raceways so the carrier doesn't gall with the Cerakote during cycling. The Nickel Boron BCG's work really well in this regard. Some guns with over-sized "match" bolt carriers can and have been known to run sluggishly in the past, so you do have to be mindful of what it takes to make an AR15 run well when you start talking about changing the ID with coatings.

[Dan]

my lapping tool is coming in the mail! I'm excited to see what kinds of results this could produce.

[LRRPF52]

There's a thread on Sniper's Hide right now where a guy asked what he could do to fix his accuracy problems with his BHW .264 LBC-chambered AR15. I mentioned the receiver face squaring and extension bedding, and he did it first to his .204 Ruger, having never heard of this before.

Here are some of the posts after he received his lapping tool:

Posted by precision308: I lapped my receiver today and found that half of the receiver was nit making contact. Lapping didn't take long at all. This sounds good in theory lets hope that this helps.
Thanks everyone

Here's a post from 204 AR:

I don't care who trues and beds and who doesn't, but I proved it to myself that it can help tremendously. On the advice of Mike at Dtech I tore down an upper (that I had built) that was underperforming and sent it in to him for truing. Upon reassembling the accuracy improvement was significant; the face of that upper had been off quite a bit. I've since had a receiver lapping tool made and use it on any builds I put together. I'm a believer.

Precions308's update:

Here were my results..........
The grendel had no change in accuracy after lapping the receiver. I did not locktite anything on it. I plan on locktiteing theb barrel and the gas block and we will see how it goes. Now on the other hand I have a 204 I was never happy with. I lapped the receiver on it which was way off and I locktited the barrel and the gas block. It brought a one inch gun down to 1/2 in. I shot three quick groups with it and the largest group was just under .6 ".

Ya I'm happy too. I used blue loctite. Ill update my results on the grendel once I get them done. I ll get it bedded done thisweekend but won't get to the range untill early next week.

Well got out today and shot the gendel. After going back and locktiting the barrel and gas block ive had no increase wirh accuracy. I've contacted bhw and they told me that they would stand behind the barrel.

I switched those receivers and yesterday shot four 5 shot groups at 100yds. Group sizes were approximately .5, .7, .75,.7. I consider this acceptable. Would I like to see better. Yes but acceptable. It appears for whatever reason rather it be the stiffness of the new receiver or something was way out of spec on my other receiver it played a major role in accuracy.

I like to learn new things. For what I paid the barrel is acceptable and with speaking with bhw they were eager to help. It was a pain but now that I got consistanty I can work on the loads and hopefully improve on what it is already shooting. I will say from the results of my 204 I believe in loctiting andblapping the receiver. But I still want to know if that first receiver is out of spec somehow or if the stiffer receiver was thebcure.
THANKS EVERYONE

The upper receiver is an important component in the foundation for accuracy.

[NugginFutz]

The upper receiver is an important component in the foundation for accuracy.

+1

It's a no brainer, when you consider it. The upper is what keeps the barrel and optics aligned, and if there is any flex or movement, you will never realize true consistency or accuracy.