I'm new to the muzzleloading world and I'm wondering what the best most reliable primers are

So when you say primers I do assume you are talking about shotgun primers.

I do not know that they are the BEST, but I use Winchester W209 primers for everything.

I know Western Powders suggests 'Mag' primers for BH-209 but if you breech plug is designed correctly they are not needed and sometimes can be a detriment.

What gun are you using, and what powder?

I like the Federal in the 209's. HD.

Most on the market today are good for the right purpose without knowing what gun and what powder we will not be able to help much.

The ones that make the rifle go "BOOM" . Don't really think there is a "Best" primer. The one that works with your powder charge and makes it go off every time. I know from my rifles that Federal Fusion 209 primers work with Pyrodex RS while CCI 209 primers work with BH 209 for the most reliable loads for my rifles. As mentioned the BH 209 needs a hotter primer to use it along with the right type or style of breech plug for it.

I've got a Remington Model 700 ML in .54 that I converted to shotgun primers. It seems to like the Remington Primers. I tried the Winchester primers but they didn't seem to group as well as Remingtons did in my rifle. My suggestion is get several brands since primers are fairly cheap and see which one your particular rifle likes.

Thanks guys!

Telling us what gun you have, and what powder you use will be helpful in deciding what primer you need.

Don't underestimate the value of a good fit in your rifle. They all will make the gun fire but they all have different widths and lengths.

As Muley states, your model of gun will have a big difference on the best answer.