I have a brand new Anderson stripped lower and a 16" BCA upper in 350 legend (side charge model) sitting right here. Just waiting for PSA to ship my lower kit (7 days and it hasn't even shipped yet).
I wanted to do a pistol build, but the few places that had 10.5" or 12.5" uppers were pricey (out of my budget).
Either way, I also ordered some 20-round C-Mags from another site, but when the rest of my order shipped, they eliminated the C-Mags, said they didn't have any, even though the site showed them in stock. Had to order a couple of CMMG instead. I also ordered one 30-round Gen3 P-Mag, gonna try the trick of filing off the two ribs, seems to work according to a lot of reviews.
Since my state doesn't restrict hunting to straight wall cartridges and the fact that the round is relatively new, we have lots of ammo sitting on the shelves. I think this round will be a great home/property defense round.
Anyway, I'd heard about some controversy surrounding the cartridge and bullet diameters, so I did some research. Here's things as I understand it:
According to Winchester and SAAMI, the bore/groove diameter is spec'd at .346 and .357, the exact same as the .357 magnum. SAAMI says .357 -0.003, which means it SHOULD work with .354 to .357 bullets, however, in development, PRC was given a reamer that apparently wasn't to the correct spec. Bullets larger than .355 (9mm) wouldn't chamber in some of their barrels and the ones that did experienced dangerous pressure spikes. If you buy an X-Caliber barrel in this round, they explicitly state .355 bullets only. It seems the throat/neck area of the chamber is too tight. Some AR shooters say .357 or even .358 bullets are shooting fine, but I have to wonder if tight throat/necks are causing the early pressure signs mid way through the load data that some are experiencing.
All the factory ammo in this cartridge is loaded with .355 bullets as far as I know. If you look around, there are 350 Legend specific bullets available...all .355. The same bullets Winchester loads (150 grain Xtreme Point and 180 grain Power Points) are available in component form. Hornady has a bullet or two was well as LeHigh Defense. Browning is even loading factory ammo for it as well (I have a few boxes of their 124 grain FMJ's). The Browning FMJ ammo is cheap, $13 a box. I get the 150 grain Xtreme Points from Wallyworld for $20 a box. In my opinion, even for reloading, there's sufficient bullet choices in .355 that there is no need to go into the .357 or .358 realm. If you do, you can, if you want, resize the larger bullets down.