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Posted: 9/13/2010 11:41:17 AM EDT
Ok, I have decided to lap two of my new uppers. I got the lapping tool and lubricated it up. It was a tight fit, but then stopped part way inside. It would not go forward or back. Is there a trick to this? With two people I was finally able to remove the tool by one pulling on the upper and one on the lower using the drill in reverse (what a pain). What am I doing wrong? Both uppers are extrememly tight. I have not even been able to start lapping because they stop about 1/2 inch before the cut groove in the tool. Help...
Link Posted: 9/13/2010 11:51:40 AM EDT
[Last Edit: 9/13/2010 11:55:03 AM EDT by bloodsport2885]
What are you using for lube? Anything less than axle grease and I wouldn't do it. There's not really any trick. Mine went it but it was a little stubborn. Machining tolerances I suppose.
Link Posted: 9/13/2010 11:58:08 AM EDT
[Last Edit: 9/13/2010 11:59:25 AM EDT by rc109a]
Mulit Purpose Lithium Grease
Link Posted: 9/13/2010 1:04:59 PM EDT
I just did one. Slid straight in the front of the receiver. TIght but it went in all the way. Only lubed it with gun oil. Spun with no problem.
Link Posted: 9/13/2010 1:12:39 PM EDT
It will spin, but it is extremely tight. A slight twist the wrong way and it becomes stuck.
Link Posted: 9/13/2010 1:50:01 PM EDT
I had the same problem. I actually have to use a clamp like this to turn and remove the tool rather than via drill. It loosened up some by the time I was done but in that particular receiver I would still consider it tighter than expected.
Link Posted: 9/13/2010 2:04:54 PM EDT
I put a philips head screw driver in the indention opposite the cutting end to push it out while I spun the drill in reverse. I used SAE 30 for lube.
Link Posted: 9/13/2010 2:39:36 PM EDT
I've seen uppers at both ends of the spectrum. I've never had one that didn't loosen up by the time the procedure was complete. Either machining tolerances or anodizing could be the culprit for a tight fit.
Link Posted: 9/14/2010 5:48:24 AM EDT
I tried it again on both uppers with the same results. It stops just as it clears the ejection port. I can force it, but then it takes me 30 minutes with the corded drill to get it to back out. I don't think this is going to be worth the hassle. I thought about running a little fine lapping compund on the shaft, but for the gain that I would get at the chance of messing up a good upper, I don't think it is worth it. What do you think?
Link Posted: 9/14/2010 5:54:57 AM EDT
[Last Edit: 9/14/2010 5:59:31 AM EDT by GearHead_1]
I certainly wouldn't force it and I wouldn't lap the inside of the receiver. You should do whatever you can to insure the compound doesn't get into the receiver bore. It's possible that you have a lapping tool that is machined improperly. If that were the case and you used lapping compound you would not only destroy the anodizing inside the receiver but you could be making the fit too loose. Perhaps I missed this but which uppers are you using? I have found Mega uppers to be extremely tight.
Link Posted: 9/14/2010 6:13:36 AM EDT
I had this problem myself. I actually sent the tool back to midway with a letter explaining that I thought it was on the high side of the tolerances or out of spec. They sent me a new one that fit just right. It may be the tool.
Link Posted: 9/14/2010 6:24:46 AM EDT
They are spikes uppers. I have a third on my 6.8 that I was going to try, but I might consider sending the tool back and see what they say.
Link Posted: 9/14/2010 6:38:35 AM EDT
I had this problem with mine ... I ran some 600 grit sand paper over the part that goes inside the upper and after that it was fine. I think it was just slight machining marks or some kind of surface build-up on it ... after I sanded it I put some CLP on it and it slid right in the upper no problems.
Link Posted: 9/14/2010 8:50:50 AM EDT
I had the same issue with a BCM upper. It is now a paper weight.
Link Posted: 9/14/2010 9:08:20 AM EDT

Originally Posted By Garandboy:
I had the same issue with a BCM upper. It is now a paper weight.


How did you make your upper a paper weight?
Link Posted: 9/14/2010 10:42:46 AM EDT
I've found that if you're using a clamshell, you can get the vise too tight and it slightly distorts the upper. I loosen the vise a little and was good to go. I've also had some uppers that had tight spots, but working the tool in and out, slowly took care of the problem. When done, you could see where the anodizing was worn through. I only use a light oil for lubrication.
Link Posted: 9/14/2010 11:55:18 AM EDT
I tried loose clam shell, no clam shell, light oil, heavy oil/grease. I even lightly sanded tool. Nothing worked. When I put it in a lathe, it wobbled. I ran it across a true surface and noticed it is slightly out of true. I called Midway and they stated that they have had issues in the past. They are sending me a new one and said to keep the old one. We will see how this works…
Link Posted: 9/14/2010 12:11:00 PM EDT
Please pardon my ignorance but what is lapping?
Link Posted: 9/14/2010 12:43:26 PM EDT
Originally Posted By jaqufrost:

Originally Posted By Garandboy:
I had the same issue with a BCM upper. It is now a paper weight.


How did you make your upper a paper weight?


Ouch!
Link Posted: 9/14/2010 2:26:45 PM EDT
Originally Posted By TylerC:
Please pardon my ignorance but what is lapping?


Squaring/truing the upper's face before the barrel is installed.
Link Posted: 9/14/2010 3:01:52 PM EDT
Originally Posted By rc109a:
I tried loose clam shell, no clam shell, light oil, heavy oil/grease. I even lightly sanded tool. Nothing worked. When I put it in a lathe, it wobbled. I ran it across a true surface and noticed it is slightly out of true. I called Midway and they stated that they have had issues in the past. They are sending me a new one and said to keep the old one. We will see how this works…


Wow. Must have been made with a Monday hang over.

Link Posted: 9/14/2010 3:26:06 PM EDT
Originally Posted By Gatorhunt:
I had this problem with mine ... I ran some 600 grit sand paper over the part that goes inside the upper and after that it was fine. I think it was just slight machining marks or some kind of surface build-up on it ... after I sanded it I put some CLP on it and it slid right in the upper no problems.


Forgot to mention I did the same thing.
Link Posted: 9/14/2010 7:20:30 PM EDT
I have noticed slight tightness with the stag and bcm uppers when trying to lap them. After using a good amount of gun oil it was smooth sailing. I highly recommend not lapping on sanding the inside of the receiver. My thought would be to contact midway and see what the can do.
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