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12/29/2008 4:07:28 PM EDT
This is a newb question and my first post so please bear with me.  I have read through most of the sticky topics in the forums and haven't seen this addressed unless I missed it.

Other than the RRA Lowers not fitting or having tight fits into certain uppers (documented at top of the troubleshooting forum), are there any other upper/lower compatibility concerns?  Should all manufacturers lowers fit with all manufacturers uppers?  I don't want to run out and buy a lower only to find out that I need an upper from the same manufacturer and not be able to find one due to supply.  I found a Bushmaster complete lower today for $370, but want to make sure that it will work with any upper I might buy.

thanks,

mrbrisket
12/29/2008 4:17:00 PM EDT
[#1]
It SHOULD

like I said "should"
12/29/2008 7:08:48 PM EDT
[#2]
It's been my experience that some are tighter than others, but have never had one that just would not fit. The ones that were extremely tight, meaning I could still push the take-down pins in with my hands but had to use a punch, nail, or whatever was handy to take back apart, loosened up slightly with a little use.

They all SHOULD be interchangeable.

Terry
12/29/2008 8:11:41 PM EDT
[#3]
Quoted:
It SHOULD

like I said "should"


The way I understand it is that everything is supposed to be mil-spec. If that is the case, your two receivers should go together just fine. I've assembled two rifles, one on a Bushmaster lower, and one on a DPMS lower. I got the upper for each from the same company, Sherluk's.
12/29/2008 8:22:22 PM EDT
[#4]
Only combination I've encountered that won't work is Armalite upper and RRA lower.  This was RRA lower bought in 2008.  It worked with a RRA lower bought in 2001.  Go figure.
12/30/2008 6:09:41 AM EDT
[#5]
Except for the known tight spec issues with RRA any other upper & lower should fit together unless they just are not in spec (obviously). However, no can tell you if any upper & lower combo you may purchase will fit without trying to fit them ourselves. Only you will be able to figure that out when you get a set to try but as has been stated they are supposed to fit if made within spec. Some are & some are not as many can testify to.
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