I bought just the M5E1 tool for $37.50 from G&G. It arrived quick!
And this is my first build (still waiting on a Criterion barrel to arrive) so very interested in this topic. There are a lot of threads that simply ask if the AERO M5E1 receivers need lapping, in other words, is AERO machining beyond the norm. Not sure answers to those questions help because regardless of their machining, generally, YMMV. Videos are often lacking in coverage/quality sufficient for a new guy to approach this with confidence. I watched some accurizing videos from Criterion and sent Michael some questions.
1st, Do you need to protect the female threads unique to the M51E one-piece design from the lapping tool when refacing the receiver? A lot of lapping videos show lapping on the face of male thread extensions whereas the M5E1 turns that inside out with it’s integral free-float anti-rotation tabs, i.e., handguard mount.
2nd, Would turning the lapping axes vertical and turning the tool by hand be advisable?
3rd, When Michael at Criterion refers to a ‘sleeve retainer’ in the videos they show Locktite 409. Seems like it’s functioning as a bedding compound – So, my question was, does this adhere to both surfaces and make future barrel swaps more difficult? (something a little different than the thread runover mentioned here). I didn’t see a release agent employed so was thinking it does not – I use release agents when bedding other actions for sure. The problem with a ruined receiver here changed my mind and really makes me wonder about those future barrel swaps. Regardless, I’m wondering if holding the 409 back off the end of the last ¼” extension might be advisable to avoid the thread issue?
4th and last one, Is there any danger of negatively impacting headspace by being too aggressive with refacing the receiver face on the M5E1 receiver, or on any of them really?