[550b getting primers to seat flush or just below]

Are you sure you have the small primer cup and anvil on the press there are two different sized primer cups and you can push small primers with the large one. But the large one will hit the base of the case and not seat to depth. Been using a 550 B for twenty years and in the early days went through such learning curves with this equipment. Hope this was helpful Doc

[Soliciting Recommendations for a 6mm Creedmoor rifle to 1000 yds]

Michael there are a ton of options when choosing caliber action or make for a competition rifle . zero to six hundred yards .223 to.277 calibers do a fine job. If u want to be able to reach out to the one thousand yard mark accurately, I would be more inclined to go with .284 / 7mm through .338 calibers. There are a number of conditions that come into play at that range. First is ballistic coeficient of the bullet you are using. Next spin drift, then bullet drop, being able to compensate for wind drift. To be truly accurate. Having deep pockets also helps because your gonna spend a boat load. Good luck with whatever you choose. My personal favorite is a Springfield M1A super match 7.62x51 or .308 whatever you like to call it, topped with a custom bulllet drop compensating turret scope.

[Problems with Montana Gold 223 Bullets?]

I was reading about the problems you are with the montana gold .223 bullets the bullets are fine but operator error is probably to blame. as the rifle you are shooting is probably a 1in 7 twist AR style rifle not all bullets 55gr. can handle this fast twist rate. Speer tnt is also a bullet that will blow up at the muzzle if you push it past 2900fps or over twist the bullet. my suggestion is try them in a 1 in 10 or 1 in 9 twist rate barrel load them at or below 3000fps Hope this helps with your confusion doc