Hello,
I have bought a NDS half fence A1 lower in the past and I had to oval out the rear take down pin hole on my C7 upper with a file and dremel to fit your lower....can you explain WHY you run your tolerances tighter than spec? I would think you would want to have some play as we are building a retro rifle and NO AR is tight like that from the factory.
just concerned when I do my MK12 build and pick up a full fence A1 lower that i will have issues on running other SPEC uppers on your lower again. your work is fabulous but I am worried about pin tightness.
sorry to sound agitated, but I am looking for a spec clone and I want it SPEC.






EDIT: a reply from NDS staff in another thread:



"We use a USGI print as the basis.





However, we had to loosen some dimensions to account for anodizing build up.





And we tightened the fit to the uppers a little. Sometimes that can cause problems with certain surplus uppers."





this is what I noticed.






 

Because we wanted our lowers to fit tighter to the uppers. There is a negative perception about quality when they are too loose.


There are wildly varying tolerance on surplus uppers. You can take one lower and check it with 5 uppers and they will all fit differently.

Forgings will warp once the meat is cut out, anodizing thickness will vary, and then you have the built in tolerance range.


We are inside the allowed tolerance range of the print for a machined, in the white part. We just run on the high side of it.



If you want to make sure that you have an easy fit you can send in your stripped upper and we will check it against the lower you are buying.

We have offered this service since the beginning.

Fair enough. I wish these retro clone guys understood how sloppy a proper M16 really is and that realism = play.....but i digress.

If the uppers are all tight can i run the lower on a mill and ipen the tilerances up to a "looser" level to mimick a work A1 or is your hole lower in the recvr to add downward pressure? If i can open tolerances on a mill then i can work with that and some aluminum black to refinish :)



Thabks for the detailed info. The quality is awesome make no mistake!

If you were to attempt to "loosen" the uppers fit to the lower I wouldn't even bother with a mill.

Just put some 200 grit on a sanding block and break the finish a bit.

The anodizing is typically around 1-1.5 thousandths and a change of that dimension will give a substantially different perceived fit.


I would isolate the surfaces that are contacting each other and only work them. Sight black or candle soot work well.

Pay attention to the back radius also, not just the flats.