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Posted: 9/13/2011 1:09:53 PM EDT
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Everyone agrees some uppers have better accuracy than others but I'd like to know why!
My first ever build is an absolute tack driver and I can consistently shoot sub-MOA with it. I'm a not what I would consider a talented marksman by any measure, amateur at best, but I am very technically savvy. I read every guide I could find on building the upper and followed the instructions to assemble mine. Did I just get lucky or are they just that foolproof? The reason I ask is because I didn't spend a fortune doing it. When I total the cost of the build I'm into the rifle for about $700 including the LT BCG and LT-104 scope mount. My next build is going to be my "dream" build using a Larue lower and upper along with a matched barrel and bolt so it's going to cost considerably more. Not because I want it to be expensive, but I want to build it with certain parts I've had my eye on over the last two years. What are some of the ways to keep the accuracy of the upper on par with, if not better, than the one I built with RRA parts? |
Build it with more RRA parts 
Seriously though, to help accuracy, a good barrel, BCG, upper, and trigger group will be your best bet. The barrel and upper to keep everything solid and the trigger group to keep you as consistent as possible. The rest is just details. As long as the rest is decent quality and keeps functioning its hard to quantify the rest of the parts ability to make the weapon shoot better. But that's my 2 cents, I'm sure some will rip me to shreds. |
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The trigger is taken care of thanks to another thread of mine which worked out great.
My barrel and bolt are going to be a match set probably from ARperformance. Everything else I put on the rifle will be Larue as much as I can make it so quality won't be an issue. The biggest investment in the whole setup will be my scope which will cost almost as much as my first build did. I'm almost drooling thinking about completing my "dream" rifle. The really fun part will be the ammo and function tests before the next hunting season. Many communist cantaloupes will have to die I'm sure. |
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I've read that people going for extreme accuracy or extreme long range accuracy have their upper receiver and barrel 'trued' or some similar term. I am not very knowledgeable about it, but I'm pretty sure they make it fit without any irregularities between the barrel extension and the upper receiver ... or something like that.
The ammo used plays a big role too. |
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There are a lot of EASY things to do for accuracy. Quality matched bolt and barrel help. Lapping the receiver helps. Super triggers help. Ammo helps.Super optics help. Great fitting stocks help. Trigger time helps. Breathing rituals help. How you hold the rifle helps. Lack of caffine helps. 5.56 in a 5.56 barrel help vs 223 in a 5.56. Being able to see helps. Having a super place that is wind free (or as much as possible) helps. Having a good benchrest and seat helps. Being comfortable shooting helps.
Some people are just natural shooters, and they can embarrass you with a store bought rifle when you pull out your $2500 build. It happens. Lapping the receiver |
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Quoted:
There are a lot of EASY things to do for accuracy. Quality matched bolt and barrel help. Lapping the receiver helps. Super triggers help. Ammo helps.Super optics help. Great fitting stocks help. Trigger time helps. Breathing rituals help. How you hold the rifle helps. Lack of caffine helps. 5.56 in a 5.56 barrel help vs 223 in a 5.56. Being able to see helps. Having a super place that is wind free (or as much as possible) helps. Having a good benchrest and seat helps. Being comfortable shooting helps. Some people are just natural shooters, and they can embarrass you with a store bought rifle when you pull out your $2500 build. It happens. Lapping the receiver So what exactly are they doing to the upper on that lathe? It looks like they're just polishing the edge smooth and possibly level? |
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I just included the video for someone asking the question of what it was. There may be someone that is more experienced that can enlighten more and correct any statement that I have wrong. As I stated, I am still learning, but my understanding the lapping process uses different "grit" lapping compound to grind the face flat, or makes the end of the upper so the barrel does not cant when torqued down. You mainly read about this from people that are ex-snipers and competition shooters. I have read alot of their articles, and I have ordered the lapping tool - $35 Brownells. It should arrive soon.
Now, this doesn't necessarily mean your rifle isn't accurate when you assemble without this, but it means the process makes the barrel straight with the lower face. A 1/2 - 1 degree of cant causes quite the issue at 100 yards, but it should be consistant to some degree. If you haven't noticed, sometimes there is even some light flashing from the forge process on the end of the barrel nut threads on some cheapy lowers. The billet uppers may have a slight advantage to forge lowers here. CNC is a very accurate way of making something - However, the billet must be thicker to make as strong as the forge lower - This is a huge debate, and I don't want to start that here. Anyway, if you mounted back up sights, you probably started at the middle for the up/down, and left/right. Sometimes, you end up 2-3 lines to the left/right and up/down to hit ZERO. Does this mean that it changes when the barrel heats up? Maybe, and this lapping procedure removes this from the equation. This is why a lot of people do the lapping of the lower. Some people go from 1-1.1" MOA to .5-.7" after this process. They also go from 1" to .5" MOA from playing with ammunition and finding the sweet spot for their twist ratio on the barrel. There is also a process to true the bolt face in bolt actions, but I have not seen these for sale for AR-15s - It might be that headspace issues may arrise, and I understand that autos are not under the same guise with these issues as bolt action. Hence, matched bolts and barrels are the only thing I have seen. Lots of varibles for accuracy, and it's good to work them one at a time. ETA: I have assembled 5 rifles, and I will say that some are more accurate right out of the box as the OP stated. Just a luck of the draw. ESA: Yes, polishing it smooth and level. |
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Since my upper is a Larue billet I think I will assemble the rifle and take it to the range. If the accuracy is ok then I will just leave it set up. If not, I'll buy the tool from brownells and go from there.
On my next build that's forged I'll go ahead and lap the upper receiver. This is exactly the kind information I was looking for, thanks. |
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This is a good read and has some photos about squaring an upper in a lathe from Mod Dano523. http://www.ar15.com/archive/topic.html?b=3&f=66&t=525793 Archived so only team members can view.  |
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Quoted:
This is a good read and has some photos about squaring an upper in a lathe from Mod Dano523. http://www.ar15.com/archive/topic.html?b=3&f=66&t=525793 Archived so only team members can view. Thank you Gatorhunt! Through the link you posted I found this thread which explained my headspace question. Definitely a good read. |
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It should not effect headspace due to that being set by the bolt and the barrel extension, but I would have to read more on that subject. That is why I said on the bolt truing...It will. I think this is why companies like Midway do not sell the AR-15 bolt lapping tools.
ETA: Never mind...You found an answer. |
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