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Discussion Starter · #1 ·
WAS SHOOTING TODAY & ONE OF MY AR'S WAS HAVING PROBLEMS. IT HAS A RRA LOWER THAT I BUILT. FROM DAY ONE I HAD TO GIVE THE MAG A GOOD HIT TO HOOK UP IN RECEIVER. TODAY I DECIDED TO TAKE A LOOK AT IT AFTER SHOOTING. SPLIT LOWER FORM UPPER- INCERTED MAG (NO PROBLEM). PUT BACK TOGATHER (PROBLEM). TOOK A DIFFERENT LOWER & PUT ON THE UPPER (NO PROBLEM) NOW THERE ISN'T MUCH ON THE MAG WELL TO F.U. SO I TOOK THE CATCH RELICE OFF GOOD RECEIVER & PUT ON THE RRA RECEIVER. ( PROBLEM- WILL NOT HOOK UP AT ALL). SWITCH THEM BACK OVER (PROBLEM- WILL NOT HOOK UP AT ALL) W.T.F. ??? :'(
 

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Maybe I missed it in your summary - but do you have the same problem with that lower - regardless of what upper you put on it? Except for when you insert a mag without an upper on it?
 

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Sounds like a challenge with the lower.
 

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Hmmm...

Can you determine if the catch is somehow oriented higher in the problematic lower than in the other lower? That might explain why you have difficulty (or failure) to seat the mag - if the mag itself is contacting the bolt prior to engaging the catch.

Plan B - sell me that 'bad' lower (cheap) and your problem immediately goes away... ;D
 

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Discussion Starter · #6 ·
TOOK COLT LOWER & RRA LOWER--INCERTED A MAG IN EACH-- LOOKS LIKE MAG IS SITTING HIGHER IN RRA LOWER. :'( WHAT WOULD DO WITH A "BAD" LOWER? DO YOU THINK RRA WOULD EXCHANGE IT?
 

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I'd definitely ask. They would certainly honor a legitimate claim where it is obviously an issue with the mag catch being incorrectly machined.

Let us know what they say!
 

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Discussion Starter · #9 ·
UPDATE: HAD THE ROCK RIVER LOWER ON A LARUE UPPER AND HAD PROBLEMS WITH MAG HOOK-UP. PUT RRA LOWER ON A RRA UPPER (PROBLEM SOLVED). ALSO FOUND THAT IT WOULD WORK ON S&W MP-15T. RRA LOWER WAS NOT COMPATIBAL WITH LARUE, COLT, & CMT UPPERS. TOOK A MEASUREMENT ON MAG STICKING OUT OF LOWERS & THERE WAS ABOUT A 1/16" DIFFRENCE IN MAGS POSITION ON THE ONES THAT WORKED & THE ONE'S THAT DIDN'T.
 

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Good to hear TX. Now I am forced (out of curiosity) to try my RRA lower with my variety of uppers. Will report back...
 

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OK, so far, my RRA lower seems to work fine with the following uppers:

RRA Entry Tactical (No surprise there)
LMT MRP (12" Piston SBR)
LMT (10.5" SBR)
Model 1 (7.5" .22LR)

I did however, have failure to seat the mags (PMAGS and C Products USGI Stainless) when using a Bushmaster upper on the RRA lower.

I definitely had to give them a whack to seat fully (open bolt) and with bolt closed they would not seat - so maybe there is an issue with different tolerances / specs with RRA lowers?

I didn't have time (well, motivation) to try every lower (RRA, Spikes Tactical, POF, LMT, DPMS, Bushmaster) with every upper - but I think this is enough for me to know that SOME do not match up as cleanly as I thought.

Hope this helps, and confirms that you ain't goin' crazy! ;D
 
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