AR15 uppers and lowers

[WELSHAR15]

Will any two work together assuming both same caliber? I have a RRA a2 midlength that I love but I would like to get another and it appears that this is a much cheaper way to do it. Is there anything I should be aware of when using uppers and lowers made by different companies? Should I just go to Atlantic Firearms and pick up a cheaper Ar15? Any help would be appreciated. Thanks in advance.

 

[Davidk]

If made properly, any two will fit and work together.

 

[99si/mass]

Only thing you have to worry about is Colt size pivot pin holes. Most are regular size now but if upper is made with colt holes they are to large for most lowers.

 

[z0mbi]

Will any two work together assuming both same caliber?

The lower does not have a caliber, unless you're talking about custom lowers made for like a .50BMG AR setup or something ridiculous.

 

[Davidk]

All AR15 lowers are the same--except as some Colts as mentioned above. AR10, AR50 are different from AR15s.

Some AR15 lowers DO have caliber markings but they are just markings, the actual lower is the same. I have lowers marked 223, 5.56. 6.8, and .499. They are all identical and interchangeable.

 

[LoginName]

RRA uppers can be a hair on the tight side (at least they used to be), which is actually a good thing.

A few lite file strokes on the takedown pin lug will fix it right up for a nice snug upper/lower fit.