Can you put any AR15 upper on any lower?

Segue2002

Segue2002

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Just wondering if this can be done as long as the caliber matches. Does it make sense to buy a cheap lower and put a really nice barrel and action on it? Maybe put a nicer trigger in the lower.

Any advice helps thanks.
 
Do what your budget allows. I found that my older Norinco lower has a lot of play with my NEA upper, so if I could do it again, I'd spend a few more bucks to get a better spec'd lower.
 
well most fit. some companies have a better fit then others. but yes all AR-15 large pin upper and lowers are supposed to fit each other.
 
Yes, and the caliber doesn't have to match in some cases. As long as the magazine dimensions don't change (of the new caliber you want to use), you should be GTG. Tight fitment is another matter....

As for the 2nd part of your question, it would depend on personal taste. I wouldn't do that, but that's just my preference. Except for Norc. I wouldn't use a Norc part on a AR
 
Segue2002 said:
Does it make sense to buy a cheap lower and put a really nice barrel and action on it?
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There are many who would say that you need a Noveske lower or something similar, and also quite expensive: that is their opinion.

My opinion is you need two parts of an AR to be very good and fit you very well:

1. Stock and trigger: The stock is the part where you get cheek weld, comfort and fit. You need these things to be proper so you can shoot properly. The trigger should be the type that you shoot well with. I prefer two stage triggers because that is what is on my bolt action rifles too, so it is a constancy issue. I use a mid-line Magpul stock (and grip) and an expensive Giesselle trigger.

2. Bolt, barrel and barrel extension: These need to work in harmony to get the best accuracy and dependability from the upper. There are many issues that when they are of good quality that you don't have to worry about. I am impressed with some of the "middle of the road" upper like CORE15, as their quality is impressive.

For my upper furniture, lower parts kit and such it is all generic stuff generally: as long that that pin or spring is of proper specification it will work. Right now for a lower I would recommend almost anything other than early NEA lowers (low serial number ones have a reputation of being out of spec) and the newest polymer lowers (they need to get away from the reputation of breaking).

Of course, these are my opinions only: so take them with a hint of salt.
 
If you're doing a build consider buying a matched set... I think Saskatoon gunworks still has matched pairs by Aeroprecision, and you will get better fit. IME they're a great budget manufacturer, and actually produce uppers and Lowers for many "brand name" companies.

As stated by others, IF they're in spec the upper and lower matter much less than the trigger, LPK, and barrel.
 
I couldn't resist...I just dropped the cake on a ATRS lower. Definitely not budget, but just try to get a better fit elsewhere.
Those guys are fantastic.
 
any mil spec upper should fit any mil spec lower. You can get a min/max spec condition where you will feel a sloppier fit, but with an AR, up and lower fit has zero impact on reliability or accuracy, it's simply a matter of personal taste. (i don't like it when the upper and lower wiggle or rattle) If you have a good barrel, with the barrel extension on properly and the bolt fits the extension square, you will have an accurate rifle.

All the upper and lower do is provide a box for the moving parts and provide something to bolt a user interface onto. Trigger and stock to your preference/budget will make it easier to shoot up to the level of the barrel/bolt, but will not add to the accuracy. I would free float the barrel of any AR i want to be super accurate, but any decent barrel should shoot 1-1.5 " at a hundred and it's easy to cut that in half if you hand load and free float.

I built an AR on a armalite heavy contour 20" chrome lined barrel that i picked up at a gun show for less then 200$ (the funny thing was the fella selling it was doing so because it "wasn't accurate enough")....added an eagle arms lower (armalite, thanks wolverine!), a generic upper, and for less then a grand into it had a rifle that will punch .75 with any north american ammo and .5 all day long with hand loads. AR's have to be the easiest rifles to build on the face of the earth!

Find yourself any reputable parts, it's actually hard to find bad stuff any more..(the days of the crap cast lowers are happily over) and make yourself a rifle!
 
I think that the Colt large hole receivers are the only one I know about that aren't supposed to work.

Sometimes you end up with tolerance stacking issues, if Brand A holds to .005 inches, and Brand B holds to .019, you end up with an issue of trying to fit a 1.015" part into a 1.005" space, and it requires hammers and sandpaper to fit.
 
Thanks for all the responses. I defiantly know what I want to do. I have a Dominion Arms 556 (Norinco CQ-A). I was thinking about just getting a better trigger and a good upper, but I defiantly done want it to be loose at all.

Probably the best bet will be to build a new AR from scratch, or pick out a good spec upper and lower.
 
I have seen high dollar "custom" lowers that won't fit anything including the upper it was shipped with. I have also seen the results of experiments using heavy walled after market and fitted parts up to uppers being welded to lowers in the hopes of improving accuracy. According to the shop doing the testing, their 300m indoor range and machine rest there was zero improvement when compared to using Milspec parts.
 
My upper Norinco AR fits perfectly on my issued C7A2 lower... And vise versa. I tried once just for the fun of it. Works well in full auto too. ;)

All the AR upper/lower from different brands did fit so far. Some are more loose then others but in general they fit ok.
 
Cpt.Flan said:
My upper Norinco AR fits perfectly on my issued C7A2 lower... And vise versa. I tried once just for the fun of it. Works well in full auto too. ;)

All the AR upper/lower from different brands did fit so far. Some are more loose then others but in general they fit ok.
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:ar15: Full auto.... sounds like a dream. lol
 
Phat Eagle said:
It is for a few minutes, then you get over it and never use it again... You quickly figure out your C6 or C9 is the only proper way to rock out!

There's an easy way to get to try it.... Join the Army Reserves!
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Speak for yourself. I love FA. Not much is more fun than that. Mastering the quick burst makes it that much more enjoyable.

And yes I served long ago. But I had shot FA prior to serving and have shot FA loads of times since getting out.
 
Suputin said:
Speak for yourself. I love FA. Not much is more fun than that. Mastering the quick burst makes it that much more enjoyable.

And yes I served long ago. But I had shot FA prior to serving and have shot FA loads of times since getting out.
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This. I enjoy full auto. Not for been able to dump a 30 round mag in 3 seconds. That you get over it quick. ANd it is pointless unless you NEED to spend ammo for budjet reasons... ;) But for the small bursts... Alleyuya!
 
I have a CORE-15 lower that was well-matched to its upper but wouldn't take any other uppers, including CMMG, Norinco and DD. After the CORE-15 upper got destroyed in a stunning display of Bubbaism and replaced with an NEA upper, I needed to "machine" (Dremel) the lower to fit the NEA upper. Since then, the lower has been able to accept any upper by any manufacturer - TIGHT fit, but still.
 
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