I've just ordered parts for 3 projects but as I was selecting barrels, I came across comments about how 1/2x28 tpi threads allow muzzle expansion which creates inaccuracies and some barrel makers were crowning or using a different thread pattern for the muzzle. All three projects were to be finished with AAC Brakeout 51T flash hiders that I'd already purchased with 1/2x28 threads. One of the projects is intended to be a varmint rifle so I was going with a 20+ inch barrel (finally settled on the YHM 77TF -- 20 inches, melonited, fluted, and threaded at the muzzle with 1/2x28) but I'm wondering if I set myself up for failure with this and should have gone with a crowned or alternate thread pattern on the muzzle.

I'm curious about the claims WRT muzzle expansion. Wouldn't the muzzle device prevent this?

FWIW, the other two projects are a 16-inch carbine and an 18-inch SPR. It probably would have been cheaper to just order ready-made uppers but this will (hopefully) force me to learn more about the details of each rifle.