AR15.Com Archives
 Building first AR.. What is best upper receiver? Barrel too?
jpreedy  [Member]
11/18/2011 8:28:40 PM
Im in the process of building my first AR, just completed my lower. I have a spikes tactical lower and dpms lower parts kit if that matters at all and am going to be putting on a full length quad rail. Who are the best makers of uppers for an AR and why? Also who makes a good 20inch barrel? In terms of uppers ive heard that as long as its a reputable co and is mil-spec they are all pretty much the same. This gun is primarily for the range, small game, and when the SHTF. Any opinions? Also I am a student and money does matter somewhat but is not the only factor.

Any help or input would be greatly appreciated since I'm so new to this and can't find any forums that relate. Thanks
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zshier17  [Member]
11/18/2011 9:56:23 PM
As far as uppers go, your pretty much right. If your just getting a normal plain jane upper, any good company makes standard milspec uppers. Some companies have different little doodads here and there that seperate them from other

companies. A popular upper is Vltor's MUR, really nice upper with a few aesthetic differences. Chances are if you have a spikes lower, a spikes upper would create the best fit, but really anything would work well. As far as barrels

go, i personally love my Noveske barrel, but since your kind of on a budget, that might be slightly expensive. Rainier Arms has a good rep for their barrels, Rock River Arms has always produced great barrels at a great price. For a

budget build that still produces accuracy for hunting and SHTF, i would recommend RRA. Also might want to look into White Oak Armament.
durabo  [Team Member]
11/19/2011 10:46:59 AM
Originally Posted By zshier17:
As far as uppers go, your pretty much right. If your just getting a normal plain jane upper, any good company makes standard milspec uppers. Some companies have different little doodads here and there that seperate them from other

companies. A popular upper is Vltor's MUR, really nice upper with a few aesthetic differences. Chances are if you have a spikes lower, a spikes upper would create the best fit, but really anything would work well. As far as barrels

go, i personally love my Noveske barrel, but since your kind of on a budget, that might be slightly expensive.


this is incorrect and should not be repeated in the technical forums.

OP -

can you give a bit more info on your layout of your build, i.e. what you want to do with it... any kind of accessories you want to have? I am trying to figure out your end weight and intended uses...
zshier17  [Member]
11/19/2011 11:27:31 PM
what is incorrect with that statement? So are you saying that a spikes upper and a spikes lower aren't a good fit? because i have a spikes upper and lower and they fit great together. I didnt say the only way to get a well

matched upper/lower was to get the same one, I only said it increases your chances. Not sure what the atrocity was here.
durabo  [Team Member]
11/20/2011 12:21:36 AM
Originally Posted By zshier17:
what is incorrect with that statement? So are you saying that a spikes upper and a spikes lower aren't a good fit? because i have a spikes upper and lower and they fit great together. I didnt say the only way to get a well

matched upper/lower was to get the same one, I only said it increases your chances. Not sure what the atrocity was here.


Brand matching up has absolutely nothing to do with it when you are talking about manufacturers who machine to proper milspec tolerances. couple that on top of the tolerances from the various forgings made by a few different companies who sell to all places and you have one of those situations where fit is a crap shoot.

just because your spikes set matches up and fits perfectly does not mean everyone will or even that there will be a higher chance of them fitting and matching up tightly. it just means you got lucky.

no atrocity here, just everyday misinformation that im trying to cut down on for the new people.

besides... fit means nothing anyways except cosmetics.
Toyoland66  [Member]
11/20/2011 12:50:47 AM
Asking what is the best upper is like asking what is the best automobile. It depends a lot on what you watn to do with it, and what your budget is.

If you do some reading around this site and others you will see several names mentioned more than others. Look for something mil spec, and buy the best you can afford (just my $.02)
jpreedy  [Member]
11/20/2011 2:26:50 AM
As I said I will be using it for hunting, the range, and shtf. How do you geta good fit and what are some if the better names out there. I'm not looking for some upper that guarantees a group of 2 inch when shoutinga target the size ofa dime on the far side of the galaxy,just some ideas of manufactures of the better all around top performers for the price range of 00 to 200?
FlDiveCop71  [Team Member]
11/20/2011 2:43:35 AM
The term "mil-spec" as it applies to fitment, does not usually refer to a single, precise, exact measurement, but rather a measurement within a small range of tolerances (+ /- , ect), to which if a part is manufactured within said tolerance range, would be considered to be a "mil-spec" part.

Aside from normal machining variances, some manufacturers choose to mill their parts closer to a particular end of a tolerance range rather than in the exact middle. They do this so that a higher majority of their components may achieve a 'tighter' fit with other 'in-house' manufactured components. This is why it is usually recommended to purchase your upper & lower receivers from the same company or manufacturer.

That being said, Personally - I would take the lower receiver with me to a local gun show or shop, and hand match it to one of the uppers that are usually available at such. Most proprietors / vendors will not mind if you ask to test-fit your lower to their products in order to find a good match-up. (Just be sure to ask FIRST... )

Good Luck with your purchase, & welcome to the forum.
FlDiveCop71
zshier17  [Member]
11/20/2011 1:10:34 PM
Originally posted by durabo:
Brand matching up has absolutely nothing to do with it when you are talking about manufacturers who machine to proper milspec tolerances


FIDiveCop71 beat me to it, but he is exactly correct. Informing the OP that buying an upper and lower from the same company will get you a good match is not Misinformation. Any good company would not sell an upper and a

lower if they did not fit together well. Saying that buying an upper and lower from the same company(given a reputable comany), will not increase your chances of finding a good fit is the only misinformation on this post. We are

only trying to help the OP, and nothing I or FIDiveCop71 is incorrect or in anyway false. It is merely an opinion, your opinion is not wrong and neither is mine, however calling my information out as misinformation is wrong.

besides... fit means nothing anyways except cosmetics.


This however, is a small bit of misinformation. The tight fit between an upper and lower reciever has a lot to do with not only function but accuracy. A loose fitting upper reciever can affect everything from sight alignment to

cheekweld to carrier tilt. If a good fitting upper and lower reciever was not a desirable thing, companies would not make matching sets, reciever tensioning screws would not be manufactured into lower recievers and competition

shooters would not have a matching set made for their rifles. A good fit is just as important as any other aspect of assembling an AR-15. Assemble your rifle correctly and no matter how cheap it is, it will treat you well.
zshier17  [Member]
11/20/2011 1:20:17 PM
Originally posted by jpreedy:
As I said I will be using it for hunting, the range, and shtf. How do you geta good fit and what are some if the better names out there. I'm not looking for some upper that guarantees a group of 2 inch when shoutinga target the size ofa dime on the far side of the galaxy,just some ideas of manufactures of the better all around top performers for the price range of 00 to 200?


I have a RRA upper, a Spikes upper, and two LAR uppers, all of which are great uppers. I think RRA is a great company to buy from and work with, good solid products at a good price. Spikes tactical is also a great company,

and since you have a Spikes lower, it cant hurt. Vltor makes really nice looking uppers. But really any of the big companies out there i would trust. Rainier, Bravo Company, DPMS, PSA, Stag, M&P... honestly its just what you find

that you like the best or can find at the best price. Chances are this wont be your last build so dont overthink it too much. Just get a good solid upper and see how it performs in the end. Good luck though man, and make sure you

update with some photos and whatnot.
durabo  [Team Member]
11/20/2011 9:54:52 PM
Originally Posted By zshier17:
Originally posted by durabo:
Brand matching up has absolutely nothing to do with it when you are talking about manufacturers who machine to proper milspec tolerances


FIDiveCop71 beat me to it, but he is exactly correct. Informing the OP that buying an upper and lower from the same company will get you a good match is not Misinformation. Any good company would not sell an upper and a

lower if they did not fit together well. Saying that buying an upper and lower from the same company(given a reputable comany), will not increase your chances of finding a good fit is the only misinformation on this post. We are

only trying to help the OP, and nothing I or FIDiveCop71 is incorrect or in anyway false. It is merely an opinion, your opinion is not wrong and neither is mine, however calling my information out as misinformation is wrong.

besides... fit means nothing anyways except cosmetics.


This however, is a small bit of misinformation. The tight fit between an upper and lower reciever has a lot to do with not only function but accuracy. A loose fitting upper reciever can affect everything from sight alignment to

cheekweld to carrier tilt. If a good fitting upper and lower reciever was not a desirable thing, companies would not make matching sets, reciever tensioning screws would not be manufactured into lower recievers and competition

shooters would not have a matching set made for their rifles. A good fit is just as important as any other aspect of assembling an AR-15. Assemble your rifle correctly and no matter how cheap it is, it will treat you well.



can you show any data to back any of this up?

an intensive search here will show hundreds of threads with thousands of people who have the same company matching upper/lower and a loose fit. then you will also have a bunch of people who got lucky and get a nice fit. tolerances are just that... tolerances. the odds of getting a perfect match (especially when buying them separate) essentially makes it a crap shoot and completely random.


and the whole accuracy being effected by upper/lower fit is a complete myth brought on by people trying to apply bolt gun rules to the AR15 design. Upper/lower fit has nothing to do with accuracy in an AR15 style firearm. its just not the way it is designed.

even if you could show it being effected you would literally HAVE to lock your rifle up in a vise every time for the tiny bit of accuracy increase to make itself shown. throw that thing on a bipod/sling/shoulder and you immediately bring so many variables into the accuracy equation that the .001 difference will be completely lost.... assuming you could actually shoot well enough to notice it anyways... and if you can shoot that well then you really don't need "help" with anything, you should be famous already.

i would love to be proved wrong on any of this because if you could actually prove it then the AR world would be a much different place... but there is really just no data that shows either of these things are true, only unsubstantiated claims and samples of one.
jpreedy  [Member]
11/21/2011 2:34:26 AM
im a noob to the ar world but have been raised up around guns all my life and i do know that slop and a lose fit between the receivers will result in a horrible accuracy. if the lower moved one inch do you think that would have any impact on the accuracy? YES, the answer is an obvious duh! so the tighter the fit the better the accuracy, no myth there. its like if you were given a chain saw with the chain really loose. how well would that work? would it do the job like it was supposed to? probably not. im not saying anything to the contrary against tolerances. all manufactures are going to be able to machine with a different precision, but to have all tolerances to be within .001 plus or minus would be a whole lot better than to be at .99999. and exponentially better if you were shooting at 1000 yds. say the buffer tube was machined within tolerances of .1 and the upper within .05 and the lower with .11 and the barrel with .09, and the break with .19 and the bolt at .07. that has a total allowance of .61 hypothetical units. if they were all with .1 dont you think that would have a huge impact on the performance of the gun? NASA doesnt machine their projects to within .9999999, they go to the ten thousandths in order to provide better results. same concept here. better fit ( aka tolerances as close to 0 as possible) the better the machine will work.

the advice of going to a gun show was really good and now that i know what to look for in terms of brands i think i will go ask to try to match up my lower with a tight fitting upper.
durabo  [Team Member]
11/21/2011 7:01:39 AM
Originally Posted By jpreedy:
im a noob to the ar world but have been raised up around guns all my life and i do know that slop and a lose fit between the receivers will result in a horrible accuracy. if the lower moved one inch do you think that would have any impact on the accuracy? YES, the answer is an obvious duh! so the tighter the fit the better the accuracy, no myth there. its like if you were given a chain saw with the chain really loose. how well would that work? would it do the job like it was supposed to? probably not. im not saying anything to the contrary against tolerances. all manufactures are going to be able to machine with a different precision, but to have all tolerances to be within .001 plus or minus would be a whole lot better than to be at .99999. and exponentially better if you were shooting at 1000 yds. say the buffer tube was machined within tolerances of .1 and the upper within .05 and the lower with .11 and the barrel with .09, and the break with .19 and the bolt at .07. that has a total allowance of .61 hypothetical units. if they were all with .1 dont you think that would have a huge impact on the performance of the gun? NASA doesnt machine their projects to within .9999999, they go to the ten thousandths in order to provide better results. same concept here. better fit ( aka tolerances as close to 0 as possible) the better the machine will work.

the advice of going to a gun show was really good and now that i know what to look for in terms of brands i think i will go ask to try to match up my lower with a tight fitting upper.



Buffer tube has nothing to do with accuracy in an AR. I don't think you quite understand how an AR actually functions.

And if you have an inch worth of slop then you should not be firing that rifle.
durabo  [Team Member]
11/21/2011 7:07:04 AM
Originally Posted By durabo:
Originally Posted By jpreedy:
im a noob to the ar world but have been raised up around guns all my life and i do know that slop and a lose fit between the receivers will result in a horrible accuracy. if the lower moved one inch do you think that would have any impact on the accuracy? YES, the answer is an obvious duh! so the tighter the fit the better the accuracy, no myth there. its like if you were given a chain saw with the chain really loose. how well would that work? would it do the job like it was supposed to? probably not. im not saying anything to the contrary against tolerances. all manufactures are going to be able to machine with a different precision, but to have all tolerances to be within .001 plus or minus would be a whole lot better than to be at .99999. and exponentially better if you were shooting at 1000 yds. say the buffer tube was machined within tolerances of .1 and the upper within .05 and the lower with .11 and the barrel with .09, and the break with .19 and the bolt at .07. that has a total allowance of .61 hypothetical units. if they were all with .1 dont you think that would have a huge impact on the performance of the gun? NASA doesnt machine their projects to within .9999999, they go to the ten thousandths in order to provide better results. same concept here. better fit ( aka tolerances as close to 0 as possible) the better the machine will work.

the advice of going to a gun show was really good and now that i know what to look for in terms of brands i think i will go ask to try to match up my lower with a tight fitting upper.


ETA... Just managed to actually read that wall of text. What you are talking about is tolerance stacking, and in your example you are talking about tolerances of parts that have no real quantifiable effect on accuracy.

You cannot apply the physics of other platforms to the AR design. There is a reason that the platform is so amazingly popular, and part of that is the design itself lends it to being incredibly accurate and not really effected by things like that in regards to accuracy.


Buffer tube has nothing to do with accuracy in an AR. I don't think you quite understand how an AR actually functions.

And if you have an inch worth of slop then you should not be firing that rifle.


zshier17  [Member]
11/21/2011 12:48:35 PM
Ok, so basically what myself and jpreedy are saying is that we like our uppers and lowers to have a tight fit. I think it makes a difference and so does he. You dont think it makes a difference and

thats completely alright. Make your AR's with loose recievers and ill make mine with tight fitting recievers and we will both be happy at the end of the day. The point of all of this is DO NOT call it

misinformation. Having a good fitting reciever is NOT going to hurt, only help. So if the information given does not hurt then its not misinformation, only an opinion. And please find the nearest

competition shooter, and i dont mean 3 gun, i mean 600-1000yd competition shooter who uses the AR platform and ask them if a good fit between recievers is desirable. So this argument is over and

everyone has his opinions firmly worked out now. OP–– hope this helps and welcome to the site, just a normal day on ARFCOM. Dont forget to throw a pic of your build up on the pic thread.
durabo  [Team Member]
11/21/2011 3:42:01 PM
Originally Posted By zshier17:
Ok, so basically what myself and jpreedy are saying is that we like our uppers and lowers to have a tight fit. I think it makes a difference and so does he. You dont think it makes a difference and

thats completely alright. Make your AR's with loose recievers and ill make mine with tight fitting recievers and we will both be happy at the end of the day. The point of all of this is DO NOT call it

misinformation. Having a good fitting reciever is NOT going to hurt, only help. So if the information given does not hurt then its not misinformation, only an opinion. And please find the nearest

competition shooter, and i dont mean 3 gun, i mean 600-1000yd competition shooter who uses the AR platform and ask them if a good fit between recievers is desirable. So this argument is over and

everyone has his opinions firmly worked out now. OP–– hope this helps and welcome to the site, just a normal day on ARFCOM. Dont forget to throw a pic of your build up on the pic thread.


fair enough.

now that you have stated that your belief that tight fitting receivers making a difference in accuracy is opinion and not fact backed by cold hard data i approve of this.

carry on.

OP good luck with the build.
Streetsalvation  [Member]
11/21/2011 4:28:00 PM
That was a lot of reading back and forth:)

OP, I am as well in the process of assembling a build on paper before I buy. I am a fan, so far, of Spikes Tactical. You have a lower so it seems you might be as well. They may not be the cheapest but you could spend a whole lot more as well. What I am looking at doing is buying their upper and putting in the boron coated BCG in it. Why? Cause it looks pretty;), the idea of it functioning even better sounds good to me, and long life sounds great. I also like the fact that Spikes backs their product with a lifetime warranty. Not many people care about this, but I just like the security that if they back it for a lifetime, there might be a slight chance they have built it for a lifetime.


Barrels, I have not done any serious searching yet because I was looking at getting a complete upper.

have a blast reading to find your answer;)

Street
jpreedy  [Member]
11/22/2011 3:58:49 AM
I'm sorry, I misspoke. WhenI said buffer tubeI really meant the fit between the tube and tube female end of the stock. The fit there actually does affect tue accuracy. If that rocks and moves when shooting that will affect accuracy ina negative way because the whole rest of the gun will move around compared to the such of the gun. Which is precisely why people are so concerned with the tightness between the two and don't like any movement or rocking. Same with the fit between upper and lower. If you were to puta laser on just the lower snag one just on the upper ofa lose fitting ar at 200 yards there would only bea slight difference in the max distance between the two points. then at 600 that group size triples in size. And yes, as you called tolerance staking, not quite what its called in the engineering world, does apply to every machine, and in this case affects accuracy all the way down from the stock to the barrel
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