What is Reddit's opinion of Flitz BP 03511 Metal, Plastic and Fiberglass Polish with Paint Restorer, 1.76-Ounce, Small, White?
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I sent a note to Henry asking what they recommend, and they said Flitz Polish. Works great!

Link to Amazon where I bought mine.
https://www.amazon.com/Flitz-BP-03511-Fiberglass-1-76-Ounce/dp/B00MUG95UI/ref=sr_1_4?ie=UTF8&qid=1501675657&sr=8-4&keywords=flitz+metal+polish

Flitz polish

Flitz BP 03511 Metal, Plastic and Fiberglass Polish with Paint Restorer, 1.76-Ounce, Small https://www.amazon.com/dp/B00MUG95UI/ref=cm_sw_r_cp_api_i_DJEdBbTT9ZPF3

Use a standard AR-15 cleaning rod and load up some barrel swabs (or just cut up a t-shirt) with it and just run it back and forth until desired smoothness is reached. I use flitz on my real bolt actions to polish the bolt/receiver so they cycle smoothly.

Check out Flitz polishing paste. Flitz website, Amazon. The paste has a very fine abrasive and I've used the stuff to remove patina and rust on carbon steel (non-stainless) knives on several occasions.