So,
I posted a thread in the NRA HP Facebook group a few days ago on this. Asking those that do build their own uppers, what if anything special do they do out of say an ordinary AR15 upper build.
In other words, are there any competition secrets/tips to building a competition AR15 upper.
WOW...got several responses from some old timers that ranged from "Pay a gunsmith", to "Your crazy for building your own".
Hmmmm
But also got several tips.
It seems that many of the older shooters (from M1A days) prefer to send upper to a smith for a rebarrel. That is fine, to each their own.
Three recommendations stand out from memory:
Use a Gieselle Reaction Rod to prevent torqueing the upper receiver
SHIM the barrel extension for a tight fit in the receiver
And then this gem:
Torque barrel nut to lower end of spec. Assemble, go shoot. Then torque barrel nut some more. Assemble, go shoot. Repeat until you find the tightest groups!
WOW!
No way I intend to do that. But, it just goes to show the extreme lengths some will go to for accuracy.
I replied to the "torque barrel nut" post and asked what he was basing that from, if he had any data to share. All I got in response was that the AMU did a study/test on that awhile back.
I do not doubt that someone tested this barrel torque thing...
Also was advised to procure Glen Zedikers book, building the competition AR15 (or something similar to that).
I have that on order (available at Amazon), and will share any tips I get from that book.
Anyone in here been down the path of reaming/truing the upper receiver barrel port? Barrel Nut Torque thing? Using shims on barrel extension?
Someone else mentioned something about the shoulders in the receiver....forget what that was all about.
Interested in what anyone in here has done, out of the ordinary assembly procedures.
R/
Chris
I've sent a couple of stripped uppers out to have the barrel mating surface squared up. The company that did the machining said they were a couple thousandths out of tolerance. As cheap as the service was, I'm glad I did it.
Also, I've used shim stock on my barrel installs. In my most recent build, there wasn't a lot of slop, but enough to get a .001 shim wrapped around the barrel extension and slide in firmly. When I called I Larue, their tech told me not to. He said the clamping force of the barrel nut made the shim irrelevant.
So which is right? What's voodoo? I dunno, brother. ???
LOL - I wish you two lived close by. I know about jack about building and fixing an AR.
I notice that Chris specified "for competition," so I'll not rant about how this is wasted on Appleseed ;). However, I'm inclined to think most of this stuff is still wasted on midrange, and in particular on Service Rifle. Sure, I could have the 225 in my '68 Jeep balanced and blueprinted, but it would only appeal to me as a gearhead.
Personally, I use a vise block to torque barrel nuts, and any plastic deformation in the receiver will adjust out with the sights. That saves me the $100 for Geissele's reaction rod. The rest sounds like black arts, where you hear from this one guy's friend's uncle about One Weird Trick that will make you shoot 0.325 MOA. In addition, I'd be wary of shims, since you might have slop in there by design to account for thermal expansion of the extension.
There is a good video on YouTube from a armorer at camp Perry where he sells competition barrels. He shows how to set up and tune the barrel torque and has the guaranteed groups for eavch barrel he makes and sells. Take a look for "AR-15 Barrel Harmonics" and how the torque changes the harmonic wave location at the barrel crown where the round exits. Pretty interesting.
I just rub the tail of an albino Onager on the barrel nut. Guaranteed 1/4 MOA ;)
Seriously though, a properly torqued barrel can shoot better than me. Not sure if a high master could tell the difference with some "voodoo" done to it.
I use the Brownell's receiver facing tool to square up the receiver face. I've read enough testaments to it improving group size and allowing previously off center rear sights to be centered up that I'm willing to spend the 5 minutes it takes to do a good job of it. The fact that we "know" square and true faces are better to bolt anything against makes that one a no brainer.
I've read Zediker's books on reloading and building more than once and got far more out of his reloading for competition than his AR building one but it is a good start and reference.
Shimming the barrel makes sense if you have a loose fit. The math is easy enough to work out if needed. I'm not a good enough shooter to tell if epoxying the barrel into the receiver helps.
Unless you have a barrel nut that does not require timing on the gas tube I don't see how you could fire and re-torque without going way over max torque spec.
I too use the receiver facing tool Lomshek mentioned. Does it make a difference, I don't know for sure, but it gives me confidence to know that I have eliminated a potential source of error.
As for shimming the barrel, I understand that its main purpose is to get the groves in the barrel nut properly aligned (timed on the gas tube) without exceeding the torque parameters (not to over-torque). Maybe I've been lucky, but I have never had to use one.
I believe that if you epoxy the barrel into the receiver you will now have a very permanent upper. I stay away from it. Instead I put liberal amounts of anti seize. Seems to work, at least it gives me a warm fuzzy feeling and if I ever need to change the barrel it will be much easier. I have an old receiver that I've been trying to remove the barrel. I've tried just about everything I've heard of. It just won't budge. I suspect the builder used Loctite or another kind of adhesive.
aj
Great info.
I am taking a 1 day course in October that is an intro into CMP NM Course Clinic. I have been looking forward to this course for months. My desire is to get into that game and start going to matches next year.
I love the AR platform and my plan over the winter is purchasing a NM rifle already built. Budget minded suggestions are welcomed :).
Laredo,
Other than a NM trigger in the lower, you have a choices for stocks. UBR Gen 1, A1 or A2. You can also opt to use an A1 grip (which I prefer).
If you opt to use a scope, a MAGPUL BAD lever is authorized for use.
Other than the above, the lower is stock/as is.
Upper:
Many options here. For a decent priced upper, check out Keystone Accuracy, their A5 upper is what I have been using and it does very well. Green Mountain Barrel.
Of course you can go pricier, Krieger barrel, etc.
If you want an A2 upper with NM iron sights, Creedmoor Sports sells A2 uppers as well as many others, White Oak is another.
The A2 is a dying rifle on the firing lines as of late, with the introduction of scopes.
You can upgrade the upper, with items like a Giessele MK7 NM quad rail, but that is $$. I like the Keystone Accuracy A5 option. They use a Yankee Hill quad rail (12.5 inches) and they have modified the rail with a permanent sling swivel attached at the front.
Hope the above helps.
R/
Chris
AJ,
I have experienced extreme difficulty removing a float tube off an A2 I had bought from Creedmoor Sports. Think it was built by CLE, but had to use PB Blaster, let soak overnight, and also Kroil and heat (torch), with a breaker bar on a Ford wrench.
It will come loose, and yes...sounds like someone used locktite or something.
Maybe try the above?
R/
Chris
Quote from: Laredo on September 28, 2017, 09:48:29 AM
Great info.
I am taking a 1 day course in October that is an intro into CMP NM Course Clinic. I have been looking forward to this course for months. My desire is to get into that game and start going to matches next year.
I love the AR platform and my plan over the winter is purchasing a NM rifle already built. Budget minded suggestions are welcomed :).
Still happy with the Rock river national match rifle. After 11 years of use. The use has not been heavy, and I am fully aware that barrels are like vehicle tires that only go so many thousand miles. Have not changed the barrel yet.
I am partial to irons. However, I realize as I age I may want to change.
I have seen a2 uppers with a removable carry handle/site. My thought was if my eyes ever get to old for irons, I could take the handle off and put a scope on. Is that configuration allowed in CMP and NRA HP?
Carry Handles are allowed.
The real thing for a National Match type rifle in A2 config is that you would really want 1/4 min adjustments on the sights.
Also, it is highly recommended and desired to get the rear sight "pinned", you can research that, but it prevents wiggling movements and also is very repeatable.
A2 uppers in NM config should be really easy to find, especially considering almost everyone has swapped to a flat top upper with the scopes.
If you are on Facebook, there is a group called "The Firing Line Tag Sale" and they often have A2's pop up on there.
R/
Chris
Quote from: navybowhunter on September 28, 2017, 02:05:33 PM
A2 uppers in NM config should be really easy to find, especially considering almost everyone has swapped to a flat top upper with the scopes.
Easier to find used than new. I wanted to build one for my wife earlier this year, and White Oak was out; they said they can't source the forgings anymore, and they're saving the few they have left. Looks like Brownells has them, now, so maybe someone did another run. Your best bet is to post a WTB on the usrifleteams dot com forum, and you'll probably get one with a 1/4 minute pinned rear sight for anywhere from $80-140.
Someone mentioned cheap? If you want to do that, get the Rock River service rifle float tube kit from Brownells for $100, which includes handguards and is easy to install correctly (note that it doesn't include the delta ring/weld spring assembly):
http://www.brownells.com/rifle-parts/forend-amp-handguard-parts/handguards-amp-rails/ar-15-m16-nm-free-float-barrel-sleeve-prod9943.aspx (http://www.brownells.com/rifle-parts/forend-amp-handguard-parts/handguards-amp-rails/ar-15-m16-nm-free-float-barrel-sleeve-prod9943.aspx)
Pick up their $25 A2 front sight base that you can drill and tap for 8-32 set screws, after hacksawing the sling swivel lug off. Get a White Oak service rifle barrel for $225 and go shoot it out.
If you want a flattop upper and a free float quad rail, there's a $50 one on ebay that people on the National Match forum have recommended:
http://www.ebay.com/itm/282225960781 (http://www.ebay.com/itm/282225960781)
I put a YHM flip-up sight on my practice/loaner flattop, so I can shoot optic or carry handle:
http://www.brownells.com/rifle-parts/gas-system-parts/gas-blocks/ar-15-gas-block-front-sight-prod21446.aspx (http://www.brownells.com/rifle-parts/gas-system-parts/gas-blocks/ar-15-gas-block-front-sight-prod21446.aspx)
If you have time, you can save a couple hundred bucks vs. buying an assembled NM upper. On the other hand, you can have confidence in anything you get from White Oak, Keystone Accuracy, or Compass Lake.
Quote from: airplanejoe on September 28, 2017, 08:23:44 AM
As for shimming the barrel, I understand that its main purpose is to get the groves in the barrel nut properly aligned (timed on the gas tube) without exceeding the torque parameters (not to over-torque).
That's a negative. Shimming a barrel refers to wrapping shim stock around the barrel extension to increase the OD of the barrel extension so it fits tightly in the receiver if the receiver hole is too large.
What you're referring to would be using some kind of precision machined shim washer to help clock the barrel nut to an idealized torque.