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Posted: 1/13/2007 8:27:38 PM EDT
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Ok, so I received my WOA upper receiver from ADCO *looks awesome and they assembled the ejection port and assit* and it's not mating well with my LCW lower. Forgive me for lack of terms, but I can only bolt either the fron end or the back end, not both at the same time. With a lot of effort I was able to get both pins in roughly 30% of the way, but looks like I'll be popping them out. Can anyone suggest a solution to this problem? If it matters I already have a 4 pos CAR stock and a RRA NM trigger and LPK assembled to the lower. Thanks. Dan |
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Read thru this thread about RRA...sounds like the same troubles. Mike |
The problem usually lies in the different thicknesses of coating material. If both pins will start in............tap them in seated with a soft mallet. You will have a very tight rifle with no wobble between the upper and the lower. Oil the pins first. If you tap them in then out a few times they will get easier. There is a tacked thread on in this section on the tighness of RRA parts. Edit: Mvician posted while i was typing.
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The LCW lower I got has a mating problem also. THe front hole a little to low and I have to force the upper down on the lower the last bit. Upper springs up a little when I push the rear pin out. Tried a dozen uppers on it and all are the same. Good luck finding your problem. |
I would use the above. Idea of useing a soft. Rubber or rawhide malit. To put together. I have had some factory rifle. move about 1/8 of in side to side they were so lose. It will ease up with ware. If its realy bad. Before modifeying it. Send it back or call the maker and see what they. Say. Personaly. I perfer the uppers and lowers to be a little bet tight. 
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A new idea? Push through the front pin and file down and finish sand the rear pin where you can see the mismatch between the upper and lower. A takedown pin costs, what, $5? If you don't want to take a chance on damaging the upper and lower with forcefitting, try this. The takedown pins don't take much of the stress of firing, or should not if I understand how ARs operate. |
| Ok, so I'm still having trouble fitting the upper to the lower. There's maybe 1/8, MAYBE, of metal blocking either the front or rear... tunnel thing *yes I'm hanging my head in shame*. I'm able to only get EITHER the fron or rear, but not both. I'm getting pretty desperate and I'm close to bringing the dremel out. |
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Always connect the front (pivot pin) first. Always. Now - determine what is stoping it. It will either be too much material up front not allowing them to close, or it will be a problem with the rear lug area where the takedown pin lug goes into the lower. If the latter is the problem, repeated attempts to close the lower should show rubbing marks here. Check it out - and let us know. Typically, if you just cannot get it together, then you need to remove a little material, either in the lower area, or on the corner edges of the rear lug of the upper. |
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I connected the front pivote pin, and when i lay the back down, I can see roughly 1/8 of the upper connection through the pivote pin area. As far as I can tell nothing is in the way. If it means anything, the 1/8 of upper receiver pivote pin connection *I really do not know the correct erms* is showing from the BOTTOM; not side nor top. If it helps I am able to reverse the process. I can connect the rear, but the front will not connect. |
| It's definately in the rear lug area. Looks like i'm trying to squeeze a size 10.5 foot into a size 10 shoe if you get my meaning. It's so close yet so far. Would dremeling hurt it, assuming i don't mess up? This is my Recce build that I'm working on after all. |
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Before you start removing any metal, make SURE you understand exactly what going on. If you have the front pivot pin installed and have an 1/8" gap at the back, the amount of metal to be removed depends entirely on WHERE it's hitting. Rather than a problem at the rear, it is far more likely to be a relatively small interference up front, magnified by a large lever arm. Take a thin piece of paper (the thinner the better) and slide it along between the upper & lower on both sides with the upper & lower held together as best you can. It will probably only hang up as you get to the front. Another way to check it to try putting a thin piece of paper between the upper & lower right at the front and see A) can you pull it out, or B) does it make the problem worse? If it's B, then the front pivot pin hole in the upper may be too high. Another check is to skip the pins entirely, and clamp the upper & lower together. If you look though the holes in the front & rear, you make be able to see how far off they both are. It sounds like they may both be a little high. If the upper can rock back & forth at all, there is something in the middle that is causing a problem. In the wrong place, a tiny burr could cause this problem, and the fix may be trivial. If the pin holes in the upper are off by a significant amount, I would talk to the vendor. The alternative is to migrate the holes in the upper VERY CAREFULLY so they will fit. I would use a fine abrasive on a long rod. You want to proceed very slowly, and a long rod will allow you to see any tilt more easily. Clean the hole carefully before doing another test fit, you don't want to get abrasive in the works. If the lever arm on the interference is long enough, it may only take a thousandth of an inch to get a good tight fit. Good luck! |
This is exactly where the material has to be removed most of the time when using a CMT lower with a bushy/colt upper. |
| Gwhite has the right idea. With the takedownpin removed from lower,Insert the pivot pin then close the uppers by hand. look through takedown hole and determine where and how muchmetal needs to be removed. Use an apropriate size rattail file to get where you need to be. should only be a few hundreths or less. if its way out of specs send the rec back. Many years ago most aftermarket receivers that i came across needed final fitting. I used to use a drill and bit until learning the hard way how soft aluminium can be. |
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Interesting - I have never had to remove metal from inside the takedown pin hole. That seems like you are fixing the symptom, not the problem. The problem is typically excess material at the rear takedown lug, or an excessivle tight shoulder area at the back of the lower. I suppose if the lower to upper contact area at the pivot pin is too tight, and you didnt want to remove material at that area - one might resolve it by removing material inside the takedown pin hole, I just never have had to do that. |
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Minuteman419 brought up a failure mode I hadn't anticipated, which is that the corners of the rear lug on the upper are too "sharp", and are hitting the rear of the cutout in the lower. If that's the problem, it's an easy fix. The trick is figuring out what's not right. I would recommend against using a rattail file. Most of them are very coarse, and unless you are experienced & careful, it is VERY easy to remove too much metal. A fine half-round jewelers file would be better. You are working on an expensive piece of hardware, and you aren't getting paid by the hour. Take your time. There is a more sophisticated technique for finding where the interference is. If you can find an art store, see if you can get some powdered white pigment (Titanium Dioxide). Mix this in some vaseline to get a white grease. Paint a suspected area on the upper with a thin coating, and them put the upper & lower together. Any place they touch, you should see the white grease transfered to the lower. If there is just a smear, it may not be meaningful, but if you have a bit with a thin spot in the middle, that is likely a contact point. This is a technique used by custom gunsmiths to get a perfect fit between two pieces of metal. Ordinarily Prussina blue is used, but it doesn't work well on dark surfaces. Be careful with the white stuff, if it gets all over the outsides of your receiver, it may be very hard to get the last bits of it out of the annodizing. A quicker and less messy approach is to use a black magic marker on the surfaces you are fitting, and see where it wears off when you mate the upper & lower. The catch is that it may be invisible if your hardware has a really black annodizing job. If it's just dark grey, it may work fine. Good luck! |
| Ok, so I decided to see if something was blocking the upper and it appeared to be the buffer *the golden colored part on the buffer spring*. I took these out to try it, and the upper fit perfectly. So, would it be correct in taking a belt snader and just LIGHTLY taking off some of the buffer material? |
NO. The buffer cant do this. Something else isnt right. You need to spend some more time examinging *what is stopping* it from closing. The buffer retaining pin might cause this - if the pin is too tall, or the lower isnt drilled correctly.... but removing the buffer should not have any effect. Do you have other uppers that you can test fit on this lower? Do this: 1. Remove the buffer and spring, and the bolt carrier, and charging handle. Cock the hammer and place weapon on safe. Close the upper-lower. Does it fit? 2. Install buffer spring and buffer, hammer cocked. Fit? 3. Install bolt carrier and charging handle, hammer cocked. Fit? |
Ok - now we are getting somewhere. First - how did just removing the buffer fix the problem before, and now it is the tube? Or did you remove the whole buttstock before and not tell us? Second - what brand is the stock? |
1) I apologize for any confusions because I do not know these terms. I'm doing my best not to say "this thingy". 2) the stock is a 4 POS one I bought from Tic00 *I believe that's his name* off the EE. |
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There we go - this has already been reported: www.ar15.com/forums/topic.html?b=7&f=125&t=288199&page=3 That is where you need to make adjustments. Cheap stocks sometimes require this - it aint the end of the world. |
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