It's my understanding that Remington has quit offering reloading components: cases, bullets, etc. Don't know about primers, as I have still seen those available.
Can't speak for Winchester. As War Eagle has stated, I usually pick mine up from the classifieds or scoop 'em out of the scrap bucket at the range. Kinda hard when you shoot a few odd balls such as 6.5x55, .338 Win mag, and .38 Super.
I wouldn't be surprised if the major manufacturers are putting all their efforts into ammo production.....I can for see another ammo shortage looming on the horizon, esp. if Hillary gets elected.