Good Loctite
There are a lot of different Loctite retaining compounds available and I purchased a few different ones before settling on using this 609 version to bed by AR barrel in the upper receiver. Both it and Loctite 620 are for retaining cylinder surfaces and not threaded surfaces. After studying the MSDS and techincal data sheets, the 620 seems like a rock solid option but I chose 609 because the removal temperature to weaken the Loctite 609 at about 480 degrees F was about 100 degrees F lower than the Loctite 620. I wanted the option to disassemble my rifle if needed. I discovered my paint strip heat gun goes up to 1000 degrees F which may have made the issue moot but I do not know the maximum heat temperature a upper receiver housing can take without issue. I read once about 600 degrees F for housing temperature but not confirmed. The build went perfect, perfect placement, and perfect alignment. Note: I did freeze by barrel and heat the receiver for assembly, Criterion barrel and Aero Precision upper. I am a semi-retired engineer.
