Mounting a Meprolite on a Mossberg 500- Loctite needed?

[bk42261]

I have a 500 with a Vent-Rib Barrel that I cut off to 19 1/2 inches so the rib was cut at the solid part of the rib.
I ordered the Big Dot sight that's (supposed to be) the same thread as the bead that was OEM.
I know enough to degrease the threads, but do I NEED to use Loctite, and, if so, I should use Blue, correct? TIA for your help.

 

[herrwalther]

Blue will work. Purple is recommended for smaller screws like scope rings and even smaller screws like bead sights. "Smaller" being 1/4" and under.

https://www.midwayusa.com/product/1764445105