What parts do you routinely change and when?  Thank you.

Gas rings need to be changed when you can set the BCG down on the bolt and it pops into the carrier.

Ok, so let me get this procedure straight: I take out my bolt assembly, and put everything, bolt face down, on a table.

If the bolt carrier slides down, the gas rings are worn?

Should the bolt assembly be clean when i do this?

Clean is better but does not matter. The version I have always herd was ther bolt has to fall out of the carrier under it's own weight, not the weight of the carrier. Hold the bolt carrier group buy the carreri and point the bolt towards the floor. Be sure to remove the carrier key for this test.  Rings last a long time as does just about every other part on the AR.

Usally parts are replcaed due to lose and not being broken.

Quoted: What parts do you routinely change and when?  Thank you.

Start out by purchasing a Bushmaster spare parts kit to have on hand in an emergency. It’s kinda hard to put your finger on what parts will wear out first, but I would venture to say the extractor, spring and insert would go first. Possibly a cam pin too.

My spares have grown over the years as the number of AR’s I own has grown, but I started out with a kit from BM and it just seems to grown on it’s own!