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4/12/2018 12:49 pm  #1


Milling/drilling plates won't set onto jig

I just received my jig and am impressed. I have a AMT lower (Mil Spec) and when I put it in the jig none of the plates would drop over the pins. I noticed that the left side plate wasn't quite against the lower and found that the 'button' that sticks out where the magazine catch is inserted was not letting the jig flush up.

I used a 1/2 inch milling bit and put a small relief in and now the jig is flush on both sides of the lower.

I still have the issue of the plates not dropping on the pins. The bolts line up and can be turned in until they start to snug. Both of the pins look straight to the eye so I was wondering if anyone else had this issue.I noticed that there is one regular hole and one slightly slotted hole in the plates.

I had already purchased this lower and would like to be able to use it with this jig.

Any ideas would be great.

 

4/12/2018 6:54 pm  #2


Re: Milling/drilling plates won't set onto jig

I have used the AR-15 jig for several different sourced lowers with zero fit issues. The last one I did was not a standard mil spec receiver (see image in following post) and I had to lightly tap the plates into place.
 

Last edited by kentm (4/12/2018 6:55 pm)

 

4/12/2018 6:55 pm  #3


Re: Milling/drilling plates won't set onto jig

https://cdn.shopify.com/s/files/1/0401/8057/products/IMG_0565_1024x1024.jpg?v=1486161477

 

4/13/2018 2:18 am  #4


Re: Milling/drilling plates won't set onto jig

Mine has a small burr inside the back take down pin hole where it was drilled for the spring and pin. I also had to tap my side plates a little to get them to seat but that didn't let the top plates to drop on like some of the videos I've seen.
Does BA have any instructions or videos online?

     Thread Starter
 

4/14/2018 10:12 am  #5


Re: Milling/drilling plates won't set onto jig

I just measured the distance of the two plate pins from the inside edge of the jig to the side of the pine. I got 0.004 difference. (Left plate pin: 0.2470 and Right plate pin: 0.2430). Is that enough to make the plates hang on the pins and not drop down on the side plates?

     Thread Starter
 

4/15/2018 9:28 am  #6


Re: Milling/drilling plates won't set onto jig

Can someone who has one of the BA AR-15 lowers please mic the outside width of the trigger group pocket and let me know what dimension you get?

I finally got my plates to drop down on the side plates by shaving the outside of both plate pins. I know, not a good idea but now that I've done that only one side will bolt up. The other side is at least 1/16 to 3/32 off center on both holes.

Is there any way to contact BA besides leaving a message?

Thanks for any help. 

     Thread Starter
 

4/16/2018 7:53 pm  #7


Re: Milling/drilling plates won't set onto jig

My guess is that the "mil-spec" lower isn't "mil_spec".  It seems too wide.  Generally not an issue, except in this case.

(for pics below)

This dimension should be 7/8 (.875 +/- .010)  Our jig is designed to work with lowers that are as bad as .020 too wide. 


mil spec forging
https://preview.ibb.co/eCG17S/IMG_2418.jpg








Broken Arms receiver
https://preview.ibb.co/f5jA1n/IMG_2419.jpg

 

 

4/17/2018 2:14 am  #8


Re: Milling/drilling plates won't set onto jig

Mike,

Thank you very much for your reply. That solved the mystery as mine measures at 0.9040 so I guess I'll contact AMT and ask why they have that in their description.

I'll order a lower from you and get my build finished. Your jig does drill really nice holes through the side plates. Clean and no issues.

     Thread Starter
 

4/18/2018 3:33 pm  #9


Re: Milling/drilling plates won't set onto jig

I don't want you to feel as if you must use our lower.  Most forgings (especially Cerro) are to actual mil-spec dimensions and work great in our jig.  They just don't look as good.

 

4/18/2018 3:43 pm  #10


Re: Milling/drilling plates won't set onto jig

Your lowers do look good. That's another reason I'll be ordering one and doing a build. Thanks.

I did order one of your lowers and don't feel like I had to use one of yours. I like the extra pin enhancments on your lowers.

Last edited by ErnieHodge (4/19/2018 7:20 am)

     Thread Starter
 

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