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Posted: 5/9/2004 8:01:13 AM EDT
[#1]
Never fear, I had a same problem as you when I attempted to install a newer A2 upper on my older colt sp1 - the front pivot pin was too big for the newer smaller pin of the A2 upper.
www.bushmaster.com/shopping/lowers/nes-06.asp This offset pin solved my problem. |
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Posted: 5/9/2004 8:09:58 AM EDT
[#2]
Large pins only came on Colt products. Don't think any adapter pin is going to help you here.
The RRA/Bushy combo would have the same pin size and SHOULD go together. Your lower may be slightly out of spec - WHAT!!  A Rock River part out of spec!!. How can that be!! Recommend you contact Pete and ask for help. He has a good reputation for backing the products he sells. Good luck. |
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Posted: 5/9/2004 8:29:18 AM EDT
[#3]
It sounds like he is talking about the distance not the size of the holes try putting the pivot pin in first. I hope it works for U soon Detlef
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Posted: 5/9/2004 9:37:08 AM EDT
[#4]
This is a common issue with RRA lowers / Bushmaster Uppers.
RRA has a high rear shelf and is a bit tight fitting in the gap where the upper receiver's post slips in. I little hard pushing or "nudge" with a rubber mallet will mate your upper to the RRA Lower. Over time it will wear in, but you will need to use a derlin punch to pop the rear pin for cleaning. On the bright side, you will have one super snug fitting AR. ~ s0ulzer0 |
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Posted: 5/9/2004 10:01:13 AM EDT
[#5]
Mate the upper and lower at the pivot (fwd) pin first, then rotate the upper and lower together and try to insert the rear (takedown) pin second. Look to see if the holes in the upper and lower are off at the rear. It may be hard to mate the upper and lower at the take down pin with out force. My new RRA lower was so tight at first I could not get the two receivers together or apart with out a rubber mallet like s0ulzer0 mentioned above. Once the two receivers are mated and the pivot pin is inserted, before trying to insert the take down pin, take a look at the holes to see if they are actually off. Keep us informed. If they are off fore and aft your lower may be out of spec. If the holes are off up and down you still could have a out of spec lower but you could also just have a very tight upper to lower fit which just requires some force to mate the two. Hope I explained this clearly enough.
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Posted: 5/9/2004 10:11:19 AM EDT
[#6]
You wouldn't have the first upper receiver that was so tight that the rear pin had to be pounded in. I have a few new Oly uppers that are very tight. One of which I had to file a tiny bit. I have a Bushmaster upper in which I did the same thing.
If you go the route of needing to file, take off VERY little. A few strokes and check, a few more and check... |
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Posted: 5/9/2004 12:57:54 PM EDT
[#7]
I had a Mega lower and an Oly A2 upper that did the same thing. I gently tapped the rear pin in with a small hammer and had to knock it back out with a punch. After awhile it got to where it came apart by hand. But man was that thing tight.
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Posted: 5/9/2004 1:39:45 PM EDT
[#8]
I have the same set up and I got RRA lower from Pete. I have to push the back pin really hard to get it to fit the Bushy upper( almost hammer it in).
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Posted: 5/9/2004 1:50:06 PM EDT
[#9]
make sure the front pivot is installed properly.Does the fromt pivot lock in place with out the upper on? try both pins without the upper on.I just rebuilt a Bushie lower with an RRA kit from pete and assembled one of his lowers for a buddy,it went together fine and his bushie upper fits fine but a bit tight until we worked the upper and lower by opening and closing a bit.If all fails call pete he will take care of it..927
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Posted: 5/10/2004 5:59:50 PM EDT
[#10]
The problem IS NOT the front pivot pin, it's the rear one.
RRA lowers have a uniform rear shelf area, as opposed to Bushmaster's "oversized" shelf area. Because of this, Bushmaster uppers have a full sized square rear lug as opposed to RRA's "tapered" rear lug. Because Bushmaster rear lugs are square, and RRA lower rear shelfs are rounded, there is some fitting required. Like the old saying goes, "You can't put a square peg in a round hole." And whatever you do, DO NOT HAMMER IT HOME as suggested in some above posts. All you need to so is slightly taper the two rear corners of the rear lug on your Bushy upper and then slap some Aluminum Black on it to return it to it's nice black color. I can guarantee you will not find a better fit than a RRA lower, especially when you "custom fit" your Bushy upper. It's really very simple and won't take you more than 10 minutes. Just remember to check fit after every few file strokes so you remove just enough material. Good luck with your project! |
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Posted: 5/10/2004 6:44:53 PM EDT
[#11]
Mine worked it just needed a little 'incouragement'
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Posted: 5/10/2004 6:45:10 PM EDT
[#12]
I picked up a Bushmaster upper this weekend ($321 Complete w/night sights even, just couldn't say no to that price), and it DID NOT fit my RRA. It fit right in another lower I have. It has an Eagle on it and says POS DIV of BIG POS or something like that. It sure didn't like the RRA though, the rear holes didn't even come close to machting up. I would have filed the upper done a bit to make it work too, if I hadn't already had another lower. It still takes a tap to get the rear pin in all the way.
PS:www.helpnick.com |
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Posted: 5/10/2004 8:22:53 PM EDT
[#13]
RRA lowers are simplie out of spec! RRA lowers do not even fit RRA uppers very well and we have all heard about some BushMaster uppers not fitting at all. Every RRA rifle I have built (4) have had fit problems. After a bit of use the do loosen up but there is a lot of metal removed before this happens. Here are some pics of my latest RRA build. The rifle is unfired! I had to break down the receivers by placing a towel over my knee and giving it a good wack to the bottom of the mag well to open it up. After about 25-30 times of doing this the receivers now breakdown by hand but look at how much metal was removed in the process! All four of my RRAs have been the same way. Like the old saying goes "you get what you pay for" and I not buying any more RRA products. Just for reference, here is my Colt MT6601. It has zero play between the receivers and I have run right at 1500rds thru it. I have broken it down around 40-50 times I guess but hey your just paying for the pony right...lol... RRA upper lug   RRA lower  Colt upper lug   Colt lower  |
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Posted: 5/10/2004 8:30:53 PM EDT
[#14]
I actually consider this effect as beneficial. Like others, my RRA Match upper and standard lower had to be manhandled the first dozen times, and metal was removed from the lug. As a result, they are perfectly mated to each other with absolutely no play, tighter lockup than any other receivers I have. I'm liking it.
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Posted: 5/10/2004 8:58:44 PM EDT
[#15]
The last gun I built was made with a stripped RRA lower I got at a good price. The flat top Bushmaster upper would not fit because of the rear lug just like everyone said. Worst thing about it was I knew about this problem but didnt even think about it until I actually tried to close it! I remembered right away after that! Anyway, I took out the file and slightly thinned both the right and left side of the uppers lug until it fit. It fit snug, but it fits fine now and without the use of a hammer (dont use hammers!). I then put some Aluminum Black on the bare aluminum of the rear lug where I filed it and its good to go now.
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Posted: 5/10/2004 9:30:29 PM EDT
[#16]
RRA lowers are very tight, they are also thinner then my other lowers. I had to force a Colt A2 upper down onto a RRA lower by hand but it did go in, it looks very funny as the lower does not match the upper.
The upper hangs over the lower by 10 to 15 thousands, this will be the last RRA product I get. There are better lowers out there made by companies that care, hell they are not even members of this board. That alone shows you how much they care about us. |
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Posted: 5/10/2004 9:45:29 PM EDT
[#17]
Not to change the subject, but Jnewt, the face of the buffer in your Colt looks messed up. Does it have a puncture in it?
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Posted: 5/11/2004 3:07:47 AM EDT
[#18]
I've had exactly the same problem as described here with RRA lower and an old ASA (
) upper that I'd built a while back. A little bit of light filing at the upper's rear lug worked for me.
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Posted: 5/11/2004 4:58:57 AM EDT
[#19]
Same here with the RRA, lower matching to a RRA upper. All I did was lighlty file the upper reciver square lug at the rear corners. A very light 45 degree fileing. I don't have a problem with it. It made it a very nice custom fit. I find the RRA product to be very well made, and priced well. Mines been a Kick A$$ rifle with out a failure/ jam in over a 1000 rounds. I put the lower together myself. RRA lower with a parts kit from Georgia Persicion.Don't let 30 seconds with a file get ya down on your new rifle. She's going to treat ya right. WarDawg
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Posted: 5/11/2004 5:00:31 AM EDT
[#20]
I enjoy working with RRA parts, but it becomes tiresome when the specs vary so widely between them. Take these two RRA lowers with sequential serial numbers for example:
 Observe the variance in the following dimension:   It's no wonder that some uppers fit and some don't. These particular lowers were made for RRA by CMT. Both of them are solid performers, but CMT/RRA needs to tighten this mess up. |
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Posted: 5/11/2004 5:20:40 PM EDT
[#21]
I have to say that my preban Colt has a RRA upper on it that fits like it was custom made for it - even though it's standard production! You can't even slide a piece of paper between the upper /lower receivers and the rear pin pushes in and out snugly with just my fingers.
I also think the RRA lowers are about the best on the market. Bushmasters are FIELD rifles and are made to be broken down easily, thus the loose fit. If you notice the pics above, you will see the uniform rear shelf area I wrote about earlier. On a Bushmaster that area is relieved and made wider, which gives a lot more play. I'm not out in the jungle hunting Charlie, so a tighter rifle is too my liking. I own a BRAND NEW Bushmaster 20" A2 which requires an Accu Wedge to keep the receivers from wobbling! I've never had that problem with any of my RRA rifles, especially those built with both RRA upper and lower receivers. 
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Posted: 5/11/2004 5:29:30 PM EDT
[#22]
I like'm tight, RRA tight.
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Posted: 5/11/2004 5:47:01 PM EDT
[#23]
I have had no problem with RRA uppers, only the lowers 
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Posted: 5/11/2004 5:59:54 PM EDT
[#24]
I've got a RRA lower mated on a generic upper.
I use an accuwedge and I like the fit of my gun. Sometimes it is a pain to get the back pin in but that is usually because of the accuwedge. I think RRA lowers are nice. CRC |
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Posted: 5/12/2004 8:51:16 AM EDT
[#25]
What is that dimension supposed to be? Looking at the receiver drawings on biggerhammer.net, I can only find the dimension at the front pivot pin (0.500 +0.000/-0.004). My guess would be that, for simplicity's sake, the dimension at the rear pin would be the same. If that is the case then the variance you measured could be within spec, but the overall dimenion would be too small (~0.01 too small? - that seems like a lot to me but maybe it isn't). Since many people report tight fits with their RRA lowers and RRA themselves advertise their tight fit, I wonder if RRA deliberately cuts that slot narrower than spec (whatever the spec is)? |
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Posted: 5/12/2004 11:37:09 AM EDT
[#26]
I'd like to see some Colt, Bushy, Armalite and DPMS lowers measured just to see what some of them spec out to.
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Posted: 5/12/2004 2:45:27 PM EDT
[#27]
I don’t know what my Colt, Bushmaster or DPMS (I don’t have an Armalite) lowers speck out at, but I’ve never had any problems like you guys are describing with fitting like parts or mixing them up. I also recently bought an LMT lower, although I have yet to build it up, I have tried on different uppers and all those seem to fit right too. I have heard a lot of good things about RRA in the past, but it’s things like these that just make me cringe. How is it that everything else they have is supposed to be so great but they can’t come through on something like this. You guys are talking about pounding on your rifles with hammers and banging them around just to get them together, this just seems extremely wrong to me; shouldn’t be happening that way.
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Posted: 5/12/2004 2:53:38 PM EDT
[#28]
I think they do make the lowers tight deliberately to ensure the tight fit. My RRA lower was extremely tight when new. I din't pound it, though. I oushed out the front pivot pin as well as the rear and just pulled the upper off by holding the handguards. After a couple dozen times, it got easier to get the upper off. Persoanlly, though, I prefer a looser receiver fit. |
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Posted: 5/12/2004 3:03:35 PM EDT
[#29]
I had exactly the same issue with a Bushy upper on an Oly lower. Five minutes and a little careful file-work later, everything was good with the world.
Maybe I'm way off, but I'm of the opinion that, if you build anything out of parts from different manufacturers, you should expect a little fitting here and there. Maybe not every time, but for God's sake don't be "shocked and dismayed" about it. Just use your brain, your hands, and your tools and make it right. |
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Posted: 5/12/2004 3:17:19 PM EDT
[#30]
Or just by parts that are built to spec.. You get what you pay for.
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Posted: 5/12/2004 4:01:40 PM EDT
[#31]
Damn, with that kind of attitude I'm going to suspect you of being a Macintosh user.
You will never sell me on the whole "Colt or nothing" thing. I'm a little too much of a free thinker to accept that kind of programming. Besides, it's complete BS. Hell, the most accurate (and reliable) M16 I was ever issued was an A2 built by FN. |
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Posted: 5/12/2004 4:47:33 PM EDT
[#32]
Not tryin to sell ya on anything bro... All companys have there faults, just some have more than others.
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Posted: 5/12/2004 4:57:34 PM EDT
[#33]
I can certainly respect and agree with them making their uppers tight. My only bitch is that they don't make them consistent. The amount of variance in my own RRA lowers is striking. |
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Posted: 5/12/2004 6:15:22 PM EDT
[#34]
I recently purchased an RRA lower to use with my Colt upper until I can get my hands on a Colt lower and the RRA lower is very, very nice. It was made by CMT. It drops every mag I've tried in it, the mag catch doesn't bind, there's no wear on the face of my buffer whatsoever, and the pushpin holes line up perfectly with both the Colt and RRA uppers I have. The Colt to RRA fit is loose, but I do have almost 1000 rounds through the combo. The RRA to RRA fit was very tight at first, but it is snug and doable by hand now.
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Posted: 5/12/2004 6:44:43 PM EDT
[#35]
I have a
stag arms lower that fits perfectly to my bushmaster uppers.Go figure. After reading some of the stuff about the stag and RRA lowers though, I think I got luckly. CJ's numbers don't lie. |
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Posted: 5/12/2004 7:53:26 PM EDT
[#36]
CJan_NH, if I read your caliper correctly, your variation is only 0.003 of an inch (3 thousanths of an inch) -- not that much. While I don't have any experience with RRA lowers, I recenty got a FAB-10 lower (CA-legal fixed 10 round mag) and mated it to a Bushmaster upper. It was tight at first but I was able to get the rear takedown pin in and out using a punch (teflon coated). After about 100-200 cycling of in & out of the rear take-down pin, and some BreakFree, things have loosened up enough now that I can do it by hand comfortably.
Detlef, if you can get it to fit with a little "encouragement", keep working it. It will loosten up. Best of luck. You guys make me jealous being able to build up all these rifles. |
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Posted: 5/12/2004 8:37:33 PM EDT
[#37]
That's why I asked earlier for the actual specification. From the drawings on the biggerhammer site, the total allowable variation at the front pivot pin is 0.004 inches. I don't know because it isn't listed on the biggerhammer drawings (or I just can't find it), but my first guess would be that the tolerances at the rear pin are the same as at the forward pin, so that the 0.003 inch variance CJan_NH measured wouldn't necessarily be out of spec. Of course, that doesn't mean the average width of RRA's cut is right on spec (and it appears that it might be narrow based on the anecdotal evidence many have reported), but I haven't seen anything yet that shows RRA's lowers have more variance than others or than is allowed by the specs. Maybe CJan_NH has made many more measurements than he has presented here and it is on that entire set of measurements that he bases his "striking" variation comment. One other thing to note that may or may not have any bearing on the accuracy of CJan_NH's measurements is that he measured (based on his photographs) at two slightly different locations, with his narrower measurement made further to the rear of the receiver. It doesn't look like he made the narrower measurement so far back that the fillets interfered with it, but there is some chance the fillets had an effect and in any case it would be best to measure at a consistent location if one wishes to compare unit to unit variation. Of course, CJan_NH may have made the actual measurements at the same locations and just misplaced the caliper during the photography, in which case this is a non-issue. I also agree with an earlier poster in that it would be interesting to see the variations in lowers of many different brands rather than just RRA. Just knowing RRA's variation doesn't tell me whether it is better, worse, or the same as others. |
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Posted: 5/12/2004 10:46:37 PM EDT
[#38]
Agreed. I would like to see two or three Colts and two or three Bushmasters also measured for comparison. A couple of Armalite receivers would also be nice. Having measurements of the big four companies on at least three, if not more, of each brand receivers would be a better basis for comparison. Maybe a large group of ARFCOMers can get together somewhere and do a comparison?
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Posted: 5/12/2004 11:09:39 PM EDT
[#39]
Holding the caliper in one hand while taking a photo was pretty tricky, so before I picked up the camera I placed the caliper in the exact same location on each lower, took the measurement, and then locked the caliper so I wouldn't lose the value. While taking one of the pics the caliper moved slightly, but it had already been locked from where the measurement was taken-so the value didn't change. It should be noted that the pics I posted were only two of five RRA lowers measured. I also measured three Colt lowers and one Bushmaster lower. Of the five RRA lowers measured, two were within .0004 of each other (four ten thousanths of an inch). Ironically the largest variance was in the two sequentially numbered units that I pictured. The Colt lowers were two sequentially serial numbered preban 6601 blue label HBARs from my own collection and a postban MT6400C lower, also from my collection. The two prebans were within .0005 of each other (five ten thousanths of an inch). I measured the postban Colt and the Bushy lowers, but I don't have additional identical lowers to compare them to. I can't remember where they measured out compared to the RRAs. If anyone is interested I would be happy to measure them again and post the results. |
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Posted: 5/14/2004 9:41:53 AM EDT
[#40]
Thanks for the clarification, CJan_NH. Sounds like my suspicions were correct. As for posting all your measurements, I wouldn't ask you to go to any trouble, but if you have the data handy I would be interested. No pictures needed, just the numbers. And if you have the measurements at the front pivot pin, they would be interesting also. Again, though, this isn't anything critical to me, so please don't put yourself out unless you are interested as well.
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Posted: 5/14/2004 10:12:06 AM EDT
[#41]
I took a dremal and rounded the rear lug on my bushmaster upper to fit a RRA lower, fits like a glove.
does not require much but a little work on the edge. fits tight holds together nicely and shoots great what more could I ask for. |
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Posted: 5/16/2004 6:20:33 AM EDT
[#42]
I did the same measurement you did on 10 lowers in my stock and got less than .0005 difference. Four serial numbers were sequential the rest were between 30 and 80 numbers apart, if ran on cnc equipment 80 parts would be a 5-8 hours apart. Robert |
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Posted: 5/16/2004 6:26:57 AM EDT
[#43]
regaurdless, RRA lowers are not built to spec.. Is it a big deal, no |
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Posted: 5/16/2004 6:31:59 AM EDT
[#44]
Sorry I was editing my original message when you replied, I guess perspective of spec come into play.
Robert |
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Posted: 5/16/2004 5:19:56 PM EDT
[#45]
Same here. I would like to see some comparison numbers if CJan or anyone else has any. It would be good to see. Also, what exactly is the sped and what sort of leeway, if any, does the spec allow? I think we need to know this before we pass judgement on anything. |
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Posted: 5/16/2004 5:39:41 PM EDT
[#46]
There was another thread in the past which had a diagram and specs for the AR receivers. The section in question should be .500 to + .005 not + or - but + .005. The Colts that CJ measured then where .500 to .502 I beleive... As you can see the RRA lowers are WAY out but some people like the extreamly tight fit
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Posted: 5/16/2004 7:07:10 PM EDT
[#47]
Thanks for the additional input, RBPRECISION and jnewt.
Here is the way I interpret the information presented thus far: RRA's QC is fine, and RRA does not have any problems with maintaining unit-to-unit tolerances since measured variations are all small, within the specification, and comparable (remember, I am only talking about variation here) to Colt and others. However, it appears that RRA has made a design decision to make their receiver slot dimension (the average or "target" value) narrower than specification to make for a tighter fit between the upper and lower. Do people agree or disagree with the above summary? (edited to clarify differenct between tolerance variation and average/target specification) |
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Posted: 5/16/2004 7:16:04 PM EDT
[#48]
Thats the way I see it... Some people really like that super tight fit. Me personally, I like that just right fit, right out of the box and no tools or leverage needed to open the receivers. The RRAs do loosen up after a bit but the amount of metal that has been worn off is kinda If RRA would make them just a tad bit closer to spec that would be perfect.
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Posted: 5/16/2004 8:52:30 PM EDT
[#49]
You can have you opinion that RRA is the best lower but that is a pretty ignorant statement without taking into hard facts. Bushmasters are better lowers than RRA. Why? Because they are made to spec. An AR-15 is a combat weapon, not a nice looking sporting arm, and play between the upper and lower is spec so various uppers can be used without fitting issues. This is the whole idea behind the AR-15. Bushmaster lowers can take a RDIAS. Politically correct RRA receivers cannot. Do I want to take my mallet, punch, and file with me into the field to service my rifle? RRA lowers may look pretty and fit nice and tight but you loose important features of the AR-15 system and you get what you pay for. |
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Posted: 5/16/2004 9:37:55 PM EDT
[#50]
Well, you also have to take into account that RRA started out marketing mostly to match shooters. Most of whom enjoy a receiver with a really tight fit. My RRA was tight when new and I had to force the receivers open, but after a dozen or so times, it loosened up to where it was just tight enough and I didn't have to force it hard to open. It wears in with time and by the time you would have to take it "into the field" it would have been fired and cleaned enough times that the receivers would have loosened to the point where excessive force is no longer necessary. As far as the RDIAS is concerened, 99.999% of AR owners will never have to worry about such a thing. |
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