I don’t think it matters. I have a BCM upper on a POF lower and they fit really well and I can swivel it open.

It really doesn’t unless you are build a precision target gun. Then the tighter tolerances of a matched upper/lower will have some benefits.


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Aero receivers, and a few other manufacturers as well, have a threaded hole that allows a plastic tipped set screw to press against the bottom surface of the upper receiver's rear boss. This can be used to eliminate the play between the upper and lower, while still allowing the pin to move without tools.

If you aren't a fan of installing roll pins, Aero's M4E1 receivers use threaded pins for the bolt catch and forward assist retention. This, with the integrated trigger guard, greatly simplifies the assembly process. I don't know of any other forged receivers that have this feature.

...... and they are known to be a pita at times, especially on the trigger guard.

I've had some experience with roll pins from the LE6920 build I did. It's something I need to learn how to do, so I may as well start with this build. I have punches etc. and will get any others I need.

Get roll pin punches. Regular punches bang them up and spread them out.

^^^ This !! http://www.cotep.org/forum/images/icons/icon14.gif

Good advice^^^^


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I have received all necessary parts to complete the upper, I should have a new rifle to try out by the weekend. Woohoo!


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Update. I'm doing quite a bit of research on different brands of parts, based on some of the adivice I'm getting here, as well as some Youtube videos. I know... I should treat those with a grain of salt, but some are pretty good.





I agree. And I'm focused on Geissele for the trigger group as well, per AFJuvat.



What are y'alls thoughts on "Sharps Rifle Co." for BCGs? I'm seeing a lot of good videos on their BCGs (eg XPB series, or the "Extreme BCG). Here are a couple of videos I've seen...


https://www.youtube.com/watch?v=oJsE2gNo1ek


https://www.youtube.com/watch?v=R-AEyY7DAEI


Now, a question or two. I'm seeing a lot of videos on "Buffers" and "Buffer weights..." For example:


https://www.youtube.com/watch?v=YwvcWgNBu2Y


and


https://www.youtube.com/watch?v=Bx0ttioOBgA


I gather that they help balance against the gas system pressure for the right extraction'/ejection force, but I'm not sure how it works. Do they work with the BCG, or with the gas system in the upper? Or something else?


Question 2: Headspace.... How important is to get headspace right? I gather pretty important in avoiding a catastrophic failure...


https://www.youtube.com/watch?v=IWTpPMYW-CA


Anyway, I should be ready to start buying parts (at least the upper/lowers) by mid January.We'll work on barrels and gas systems, next.



Thanks all!