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9/19/2017 7:27:10 PM
Posted: 3/25/2006 12:10:34 PM EDT
I tried to put a 20" A2 upper on my new RRA Lower. The rear of the upper hits on rear of the lower not allowing the pin to pass through. My other bushmaster upper fits the RRA lower, so the question is: Is the RRA lower rear cut out milled for RRA uppers or is the Bushmaster upper not milled enough to fit the RRA., it is about three C hairs shy of fitting I am debating on weather to mill some off the bottom of the upper enough to fit. Has anyone had any problems with other uppers on RRA lowers
Thanks in advance.
Link Posted: 3/25/2006 12:12:30 PM EDT
Link Posted: 3/25/2006 12:17:17 PM EDT
It is off enough that you couldn't force the pin through the hole. My guess is the bushmaster lower is milled more generous than the RRA but I have never encountered the issue before.
Link Posted: 3/25/2006 12:55:17 PM EDT
I have had the same problems with my Bushmaster Uppers on two RRA lowers (and a Century). Bushy uppers seem to be tighter than others. Neither one of mine would close near enough to fit the pin in. I tapered the upper edge of the lower with a dremel to fit. Just slight, don't go crazy, and you don't have to remove metal all the way down. It is the upper edge that hits and keeps it from closing. Yes the upper and lower will still be tight together when you are done, if done correctly.
Link Posted: 3/25/2006 2:12:15 PM EDT
I would sand down thereaer lug on the UPPER not on the lower. I had to do this on mine. It would not even go down a 1/8 of a inch into my lower.
Link Posted: 3/25/2006 2:24:18 PM EDT
I've had this same tight fit issue with RRA lowers. Tap it together and shoot the heck out of it. The first few times it will be real tight. It'll wear in and be fine.

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Link Posted: 3/25/2006 2:27:27 PM EDT

Originally Posted By Colt_SBR:
I've had this same tight fit issue with RRA lowers. Tap it together and shoot the heck out of it. The first few times it will be real tight. It'll wear in and be fine.



+1

Link Posted: 3/25/2006 2:37:14 PM EDT
Originally Posted By Colt_SBR:
I've had this same tight fit issue with RRA lowers. Tap it together and shoot the heck out of it. The first few times it will be real tight. It'll wear in and be fine.

Mine would not close at all. Filing the upper down may take longer, and may not work.
Link Posted: 3/25/2006 2:38:56 PM EDT
What the problem is the radius in the lower and the corners of the upper lug. All I did was lightly file the REAR corners of the upper lug. Just break the EDGE. Like put a SMALL 45 degree on the REAR edges. It's all it take. I barely broke my edges and she now fit's snug but not ( Need a hammer two get them apart tight ) .. LOL...RA products are great. This is a non problem , problem. Congrads on your rifle. WarDawg
Link Posted: 3/25/2006 2:40:35 PM EDT
[Last Edit: 3/25/2006 2:41:35 PM EDT by FishKepr]
If you decide to grind something, consider grinding the pin instead of one the receivers. That way if you screw up you're out a $3 pin instead of a $120 receiver.
Link Posted: 3/25/2006 2:45:31 PM EDT
Before you do all that, make sure the buffer tube isn't protruding into the lower receiver.
Link Posted: 3/25/2006 2:56:42 PM EDT

Originally Posted By WarDawg:
What the problem is the radius in the lower and the corners of the upper lug. All I did was lightly file the REAR corners of the upper lug. Just break the EDGE. Like put a SMALL 45 degree on the REAR edges. It's all it take. I barely broke my edges and she now fit's snug but not ( Need a hammer two get them apart tight ) .. LOL...RA products are great. This is a non problem , problem. Congrads on your rifle. WarDawg



This is what I did. But it sounds better the way he said it. It is at the top edge of the receiver where it meets the upper that it catches. On my wife's rifle I fitted it slowly with a small file, it is still a tight fit and works fine.
Link Posted: 3/25/2006 4:23:14 PM EDT
+1 That is what I did. My DPMS upper would not quite close on the Dalphon lower. I carefully filed off the edges of the rear lug and it fits very snug now. I use a golf tee to push the rear pin out but I can push it in by hand. Kinda scary but it does work. Do a search for Dalphon in EE to see the pics of the rear lug the original owner posted. His pics show what he did, pic is worth a thousand words right?
Link Posted: 3/25/2006 4:26:47 PM EDT

Originally Posted By FishKepr:
If you decide to grind something, consider grinding the pin instead of one the receivers. That way if you screw up you're out a $3 pin instead of a $120 receiver.

It is not a pin issue, it is the rear lug that is the issue. When I built my RRA before everyone was buying them I had the problem so I used my brain and fixed it. Now after some years of use it is still nice and snug. If you need to do it like I had to do. Just usea very fine sanding disc on a dremal and take your time and small passes at it. Just dont grind at it, make it fit like a gunsmith would do. OH it took me about 5 minutes to do it with the right tool. I am a jeweler so sanding stuff gets exspensive when you are grinding down on 14K.
Link Posted: 3/25/2006 6:04:26 PM EDT
It looks like the rear lug is the answer. Tapping is out of the question, it is out not just a little snug but stopping short. Taking out the buffer is good info, which I did when I was tryin to figure out the problem. I always hesitate when I have to take a dremmel to one of my rifles.
Link Posted: 3/25/2006 6:11:53 PM EDT

Originally Posted By gm168gr:
It looks like the rear lug is the answer. Tapping is out of the question, it is out not just a little snug but stopping short. Taking out the buffer is good info, which I did when I was tryin to figure out the problem. I always hesitate when I have to take a dremmel to one of my rifles.

Just remember if you use it ,light pressure, slow speed and light grit like 400 . Just skim it ,make even strokes. Take your time. Or use a file. If you are good with any hand tools you will be ok.
Link Posted: 3/25/2006 6:23:43 PM EDT
I run into this alot. I use a very fine stone and just hone the two rear corners until it will just close! A little will go a long ways and when done, due to the fine stone, it will not mar the inside of your lower as much.Hope this helps!
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