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4/14/2015 1:48:06 PM EDT
This is my second AR build and I am becoming more and more frustrated with free float rails impeding with the lower alignment therefore not allowing the pins to go through. Two builds, two different rails, two different uppers and lowers, same result. I end up having to back out the rail to allow the pins to align. The face of the upper receiver should not allow any rail to impede with the lower alignment. Is this common among  builds, could I be doing something wrong, or is this a design flaw since the AR platform has more options than a Lego set?
4/14/2015 2:18:44 PM EDT
[#1]
I would need pictures to understand visually where you are running into problems.
4/14/2015 3:29:22 PM EDT
[#2]
What rails?   I've only ever had that problem with cheap chicom rails. Luckily they're cheap and usually temporary so trimming them is not an issue.
4/14/2015 3:37:54 PM EDT
[#3]
I share your frustration and have run into this also when installing a Yankee Hill rail. I too had to just back it of the receiver a bit more than I wanted.
4/14/2015 5:30:12 PM EDT
[#4]
I'm gonna go out on a limb here and say that it's probably not the mil-spec receivers that are the problem.  
Have you contacted the company that makes the rail?
4/14/2015 6:14:33 PM EDT
[#5]
Quote History
Quoted:
I'm gonna go out on a limb here and say that it's probably not the mil-spec receivers that are the problem.  
Have you contacted the company that makes the rail?
View Quote


No not yet but now I have a small gap between the rail and upper (slightly thinner than a credit card) is that acceptable?
4/14/2015 6:16:12 PM EDT
[#6]
Quote History
Quoted:


No not yet but now I have a small gap between the rail and upper (slightly thinner than a credit card) is that acceptable?
View Quote View All Quotes
View All Quotes
Quote History
Quoted:
Quoted:
I'm gonna go out on a limb here and say that it's probably not the mil-spec receivers that are the problem.  
Have you contacted the company that makes the rail?


No not yet but now I have a small gap between the rail and upper (slightly thinner than a credit card) is that acceptable?



There shouldn't be a gap and never had the problem you are having. What rails are you using?
4/14/2015 7:09:05 PM EDT
[#7]
My jp tube is notched out on the bottom side to allow for clearance. It also has a small gap between the tube and upper. It isn't a big deal because the top rail bolts on and the holes are slotted so you can butt the rail up next to the rail on the upper. If you don't bridge the gap with an optic then I wouldn't be concerned with a small gap.
4/14/2015 9:03:26 PM EDT
[#8]
Quote History
Quoted:



There shouldn't be a gap and never had the problem you are having. What rails are you using?
View Quote View All Quotes
View All Quotes
Quote History
Quoted:
Quoted:
Quoted:
I'm gonna go out on a limb here and say that it's probably not the mil-spec receivers that are the problem.  
Have you contacted the company that makes the rail?


No not yet but now I have a small gap between the rail and upper (slightly thinner than a credit card) is that acceptable?



There shouldn't be a gap and never had the problem you are having. What rails are you using?


I am using a no frills $70 10" keymod. This is what I get for being cheap. Anyway the rail is on super tight (probably 60+ ft lbs) it definitely isn't going anywhere and for now I am going to have to live with this slight gap, until I can upgrade to a better quality rail. I will post pics of the gap tomarrow. Thanks so much for all the support.

4/15/2015 9:34:18 AM EDT
[#9]
I have been using YHM tubes and I have never had that problem.
The gap on the top rail is going to vary between tubes.
4/15/2015 2:49:24 PM EDT
[#10]
This is the gap I must live with for a while. The rail itself is nice and tight.
4/15/2015 5:39:38 PM EDT
[#11]
For an YHM build your lockring is too far back.
4/15/2015 6:56:56 PM EDT
[#12]
Quote History
Quoted:
This is the gap I must live with for a while. The rail itself is nice and tight.
<a href="http://s1222.photobucket.com/user/Doug_Cruz/media/20150414_205041_zpsnfzhojqv.jpg.html" target="_blank">http://i1222.photobucket.com/albums/dd490/Doug_Cruz/20150414_205041_zpsnfzhojqv.jpg</a>
View Quote



Trim the ring, if for some reason you feel that may be a problem down the road, order a spare from fleabay before grinding.
4/15/2015 8:25:36 PM EDT
[#13]
This video shows the exact problem I faced. When I tried to get close the rail hit the upper not allowing the final rotation. So i backed it off just like he does in this video. The Midwest Industries rail installs just like mine. Apparently a small gap is totally acceptable.
https://www.youtube.com/watch?v=qJyx-OVAJtA
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