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Posted: 6/6/2005 5:37:26 PM EDT
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I have a Rock River lower that only works with one of my four uppers. It won't mate completely...cannot close three of the uppers enough to get the rear pin through. It does work with one Bushhamster upper but won't work with a Colt upper, another Bushy upper and a CMT upper.... Not really interested in breaking out the Dremel... Input appreciated... |
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From RBPRECISION.com web pages under applications: "Fitting a Rock River upper to you lower. (Tight fit? We can help) All of the Rock River Arms lowers are an extremely tight fit, they need to be worked in the following way : For the love of God make sure there is no rounds in rifle and it is on safe, the hammer will need to be back in the cocked position!!! Our lawyers make us tell you that death is possible if this is loaded when you perform this, we like our customers please do not shoot yourself! 1. Assemble the front pivot pin to the upper. 2. Lubricate the rear lug completely with a light grease (best) or oil, lube the inside of the receiver also. 3. Ensure the rear takedown pin is completely out in the open position (detent is holding) 4. Slowly push the 1/2's together, they will stick (THIS IS NORMAL) it will most likely not close completely at first this is normal. 5. Open and close, repeat being careful to keep the halves aligned, do not slam them together but continue to use increasing force to fit together, when almost completely together use a nylon or soft rubber mallet to tap upper receiver into final position. 6. When they are seated (little to no gap between upper and lower) lightly tap the rear takedown pin into place. This will seem scary to a beginner but it is natural for a tight fit. 7. You may see some of the anodized removed from the rear lug at the corners, AGAIN, this is normal. 8. You may have some difficulty separating the upper and lower, with barrel up and rifle unsupported (hanging in the air) grasp the rifle by handguard and give a "smack" to the top of the buttstock, you may need to do this repeatable, usually 5-10 times will do the trick." |
Do a search, this is very common with RRA lowers. Its better to risk being too tight, than too loose. |
bigbore is right. I read an article quoting the owner/founder of RRA saying that they intentionally manufacture RRA lowers slightly out of spec (larger in some critical areas) to "ensure the tightest fit in the industry" Thats great, but occasionally results in your type of issue Apparently there is a variance in the dimensions that makes interchangeability possible. Unfortunately it also makes sloppy fits possible- and "no-fits" - albeit rare |
I guess my only question would be - What's wrong with being in spec? The tight fit does absolutely nothing for the function of the rilfe and is a PITA for new rifle owners. This seems like a silly thing to do to any part of a rifle. |
| My 2 RRA's were like that when i first pieced them together, but after putting some rounds through them, they loosened up so it's easier to take down and put together. There is absolutely no give between the upper and lower when they're put together. I like the way they fit. |
+1 You can send it back but the next one will likely be the same way. If you don't like it and\or do not want to have to file the lugs on your uppers. Let me know. If you live in the northern part of the state and want to get rid of it, maybe we can work out a FTF deal? |
Nothing is wrong with spec, but RRA deals mainly with the casual shooter. I can promise you, if they were made to spec, and went together loose you would hear a lot more complaining about the loose fit, than you hear about the tight fit. |
Is this the same guy who said they developed the "new" 1913 rail specs  . Sure, I'll take his word for it. -Justin |
FWIW, if that quoted statement is true and the company admits to purposely making something out of spec, what does that say about the rest of the product. I'll get bashed for that statement and don't really care, but I would not be happy with having to deal with some of these lowers. Filing/fitting parts just to make them fit, as is the case in some of the combos that go together, is unacceptable in my book. People are always bashing Colt for their "out of spec" items, why not RRA? Because RRA is cheaper? |
Believe me, I can see your point but I don't think it's a fair comparison in this case. While I’ve never heard Colt’s “official” reason for changing the specs on civilian AR’s, I believe it’s generally accepted that the reason they do it is P.C. in nature. It’s their attempt to make it harder for Joe Blow to convert their AR into a select fire weapon. More then likely it’s an attempt at a legal CYA. Regardless of the reasoning behind it, none of the changes they’ve made through the years could be considered an “improvement” or a useful change. What RRA has spec’ed for the rear takedown area of their lowers does help insure a tight fit. I realize that a tight upper-to-lower fit does nothing to increase the accuracy or reliability or the AR platform. I have seen some people try to claim a loose fit between the two actually helps increase reliability but I call BS on that. In my opinion, the fit between the two does little-to-nothing to effect the function of an AR. That said, some of us hate loose fitting weapons. I don’t want to hear my weapon rattle around as I move and will take steps to prevent it. The other thing to keep in mind here is the stacking of tolerances. Not all uppers need to be “fitted” to all RRA lowers. From what I’ve seen here and have experienced myself, I’d say in most cases “fitting” is not necessary but if you happen to get an RRA lower on the skinny side of the measurement and an X-brand upper on the fat side, then it might be time to whip out a file. I have two RRA lowers and have tried a number of uppers on them. The only one that required a file to make it fit was (ironically enough) an RRA upper. I’ve had Colt and LMT uppers on them and they fit like a glove. It is what it is. Some people love it and consider it a “feature”, some hate it and consider it a “flaw”. To be honest with you, I hated it at first but the first upper I tried it on was that RRA but since then I’ve grown to really like. YMMV |
All good points and all well taken. Due to this fact, I would never buy an RRA lower sight unseen. I'd like to try a few upper receivers to it to make sure I don't have one overly tight. I still haven't owned an RRA lower. I guess I don't feel I'm missing much. 
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Why? loose doesn't affect accuracy, and is easy to field strip. The most Accurate M16 I ever was issued has such a loose fit I could practically aim through the gap. I don't mind loose fit. It's really not an anomaly with the Stoner system. |
That's what so cool about having all the options we have. If you don't care about how tight the upper and lower lock up or, if for some reason, you actually like a loose fit then I would suggest something other than RRA FYI - This holds true for Stag lowers as well as they are milled to the same spec and some people have reported having the same issue with their Stag lowers. Both are milled by CMT. ShelbyGunner - my offer still stands if you decide you don't want it and you're not too far away? |
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