What I am looking for is a good 16 inch carbine barrel, chrome-lined, 1:7 twist, 5.56 chamber. Doesn't have to be a precision barrel, but decent accuracy and very reliable.
YHM is probably going to do that for you. I believe the barrels they sell are purchased elsewhere, probably from Wilson (Wilson the barrel company, unrelated to Wilson Combat.)
The Spike's Tactical barrel is probably at least as good. The BCM barrel is probably a little better, but the improvements may be undetectable in a sample size of 1.
You might want to check prices on the Daniel Defense hammer forged barrels before buying. Some of the DD 16" barrels don't cost much more than button rifled barrels, and they are likely to last considerably longer.
Accuracy is going to depend on:
-your skill
-your ammo
-your forend setup (free float or conventional)
Probably in that order. If all are great, maybe 1-1.5 MOA, if not, it goes down from there. Most military type ammo will only do about 3 MOA in 10-shot groups anyway, so you really need match ammo or handloads to have the barrel be a limitation.
Durability depends heavily on shooting style and accuracy expectations. Slow fire expecting 3 MOA, I would expect 20k rounds of barrel life. Machinegun usage (presumably on a pre-86 registered MG...) you might only get 3-4k. If you expect really tight <1.5 MOA accuracy, again 3-5k is probably in the ballpark. Moderately fast firing and expecting 2-3 MOA, maybe 10-15k. These are just off the cuff, ballpark numbers. Even the 3k numbers represent ammo costs of several times the barrel cost.
