also looking to buy some ammo in bulk (.223)? anyone reccommend a website/brand?

.223 / 5.56 : Ammunition To Go

Ammunition - .223/5.56

There are others but I have used these two and know they are good to deal with. Check the sights frequently to find good deals , then, order as much as you can while the bargain is on.

The new Wolf ammo is fine in the M&P 15 sport. The label is WPA, or Wolf, or TUSA. Black boxes, yellow/ red writing. I have already sent 1500+ WPA through my rifle. Not 1 FTE, not one FTF. Cost is about .19 per round- $190-200 per 1,000.
This ammo is steel cased, and has a black teflon/ polymer coating. No reloading. NOTE: This is NOT the lacquer coated brass Wolf used to sell. Better primers, better powder. In so far as cleaning the gun (Dirty powder issues) this ammo runs pretty close to my Federal 5.56 ammo. I have sent as many as 550 in a single session, with no cleaning. No problem.

I talked to a guy who runs several rifles at a time. His ONLY time with issues from the Wolf family ammo is when you start with 200-500 rounds of Wolf, and then switch to brass cased ammo. Brass swells, steel does not. If you shoot a lot of ammo in a steel case, then there might be some build up in the chamber if not cleaned. If you throw in some brass ammo, it is possible that the brass will expand and stick a bit, causing the extractor to maybe jump the rim, or rip the rim off the casing.

I flirted with it to see if I would have issues. None so far. I keep a chamber cleaning tip, and after a while I will give the chamber a quick scrub pass with the brush, and not worry for another 300-500 rounds.

And, finally- DO NOT run .22LR through these guns. Get the dedicated upper as was suggested.