What size primers do I need

Lyman 50th says Large Rifle for 6.5 Creedmoor.
You really need to get a reloading manual. Reloading is NOT about guessing.
You are, however, in the right place to ask questions!

Yes get a reloading manual and read all of the early chapters about the basics. Then read it again. Go slow. When you find the load data for your caliber, it will specify what size primers to use.

Welcome to The High Road and reloading!
A reloading manual is essential. For someone starting out there is a lot to learn besides which primer, how much powder and what bullet type. Published load data assumes a basic knowledge of reloading. Don't skip this part.

I’m going to pile on the get a manual. Personally I like the LEE one as it’s well written, but any of the major ones will do. I’d also suggest watching as many YouTube videos as possible.

Once you read the section on the basics, I’d suggest rereading several times. Then get a second manual from a different author and do the same.

I’d also suggest reading as much here about reloading as possible.

If you cant get or find a manual, i hear Lyman 44ed is available on the web as a pdf

Two things:

1) Winchester 6.5 Creedmoor uses large rifle primers

2) For unknown primer size brass/cartridges, small primers are .17” nominal diameter, while large primers are .21”. Even with a ruler or standard tape measure, this is pretty easy to discern - small is slightly smaller than 3/16”, while large is slightly larger.

More than one manual is a good thing ! I Makes good reading when you're in the " Library" and thinking

Federal is the one you have to watch out for, it has both small & large primers.

Mason1667 said:

Boy do I feel silly, I truly figured primer diameter would be too close to be able to tell the difference with just a ruler so I didn't even look but that would have saved me from unnecessary anxiety

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When in doubt, always ask. What you may not realize is that there is so much that you don’t yet know, you don’t know the right questions to ask to get all the correct info you need. Get some manuals, read the front section a couple times each as that part explains the process and will familiarize you with the terminology. Then read as many of the posts here as you can and as you learn more, you will know which questions to ask to learn what you need to know. Don’t feel bad, we all started out at the same point, and many of us did it before the internet.

Mason1667 said:

Like it says I need help figuring out what size primers to use, I've searched all over and haven't found help yet. I just got into reloading and have a bunch of "Winchester deer season xp" shells chambered in 6.5 creedmoor. I'm assuming they'd be large rifle but I'm still too new to be confidant in my guess. I'd really appreciate help.

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OK, it helps to get the terminology right, especially with ammunition and the reloading of ammunition.
Shells are for shotguns and Artillery. Rifles like your 6.5 Creedmore use cartridges, often abbreviated as rounds.
As AK hunter points out, it is one of those calibers that is made with both size pockets. As you can see, the difference is visible.
+1 on getting more than one manual; I suggest the Lee manual to start with, it's the best one for a beginner.
If possible, find someone who can walk you through the basics; reloading is better learned in person, though manuals are essential and You Tube videos can be helpful.

There are many free downloads for free manual to include western powders and online versions from hogden. Download one and do a cover to cover reading.

Welcome to THR!

Mason1667 said:

I'm assuming they'd be large rifle but I'm still too new to be confidant in my guess.

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Assuming and guessing in reloading can get you in to trouble. In addition to manuals that have good primers - that’s a primer, not a primer, there are YouTube videos.
You’ll also see magnum primers, just to confuse you a little more. The reloading manuals and published data will be your best guide in what to use. Let us know how the reloading goes. Good luck.

In the 6.5 CM it can be either, SR or LR. Lapua says the SR is better, produces less SD numbers. You can buy it either way, so buy the brass according to what you have in stock.

Read a manual, it will answer questions you don't even know about yet.

First welcome to THR and all us goofballs that reload.
Lots of tools and components are in short supply as we are in a drought of all things reloading. Primers are the most sought after thing now. They will sell for $100 per K (thousand) or more and when shipped have a Haz Mat fee along with regular shipping. Primers should cost $35-$45 when things go back to normal-ish, hopefully that will be soon. The key to it all is a loading manual with the how to in the front. The Lee second edition is a good one to start with. Might be able to get something at a public library that you can read without buying. Ask questions, we will be glad to help but if you read some first the answers will make a lot more sense. At the top of this section is a reloading knowledge sticky where after reading about reloading those threads will answer a lot of your basic questions without having to post alot. You will be an old pro before toy know it.

The problem with coming here to ask questions is like peeplwtchr said, you don’t know what to ask. Like others have already said, get a manual, even an old one, and read the instructional part at least twice. It will answer questions that you didn’t even know you had. Then come ask the forum what you don’t understand about what you read. Reloading is a very methodical activity when done correctly. As is learning to reload correctly. Don’t get ahead of yourself. Have fun and be safe.

I don't know that "read the manual" is all that helpful to a new reloader. Maybe I'm just a visual learner. I was fortunate enough to have an uncle show me how to load in the pre-internet days. But now, I'd watch a good youtube video or 2 to get an idea of the overall picture and to develop vocabulary before reading a manual.

But to primer sizes, yes, the creedmoor is a dual primer size round. Probably it only needs to be a small primer round, but the parent case is a large primer case, so for production simplicity I imagine that is why we have large primer cases. 45 acp is also a dual primer size.

Buy the ABC's of reloading. Available on Amazon for 25 bucks. When your done with that you can move on to DEF.

Remember your just not risking your own face, your risking the safety of people around you.

We were all newbies once but I didn't dare ask questions until I read a few books and watched a few youtube videos. Do your DD.

https://www.thehighroad.org/index.php?threads/missed-it-thank-god.888565/

@Mason1667 welcome to the forum and the world of reloading.

Personally, I’d recommend any brand name reloading manual long before unspecified Youtube videos. How will a newbie know a good video from a bad one? Experienced reloaders can pretty much separate the wheat from the chaff in the world of YT reloading. Newbies, not so much. And there’s a lot of chaff on YT. ymmv