Please note that this article looks at research and testing done by a variety of sources. Extreme caution should be taken when creating loads that go against accepted load data. This article looks at theory and our experience, and should not be considered recommendations about primers for the 204 Ruger. When developing a new load for your 204 Ruger, or any caliber, you should start with smaller amounts of powder and pressure and work up gradually.
About the 204 Ruger Cartridge
The 204 Ruger is a fast shooting small caliber round, and is one of the less common rounds that you can get an AR-15 chambered in. It’s a flat shooter, and is derived from the same parent cartridge as the 223 or 556. I first discovered the 204 Ruger when I accidentally cut a 204 Ruger cartridge down to make a 300 blackout cartridge, thinking it was a 223 from some range bras I picked up.
What size primer does 204 Ruger take?
The 204 Ruger cartridge takes a small rifle primer. Some reloading manuals, like the Lee and Nosler handbooks, list regular small rifle primers in their load data, while others recommend either small rifle magnums, or the #41, which is a harder magnum small rifle primer with a thicker cup.
Hornady Handbook of Cartridge Reloading
Can you use small rifle magnum primers in 204 Ruger reloads?
Yes, some reloading data are made with small rifle magnum primers. Hornady is one example of one that has their load data calculated with small rifle magnum primers, namely the Remington 7 1/2 primers. In theory, magnum primers are more efficient and require slightly less powder to get the same velocities and power. If they cost the same and your manual is calculated in magnum primers, I’d use magnums. The powder savings is only a couple tenths of a grain, but that can add up.
I asked my personal gun smith, who also taught me to reload his opinion on small rifle vs small rifle magnum and this is what he said about it: “I’ve tried both. Small mag is if you want fast loads. You need to burn a lot of powder quickly. You can over pressure the case quick so be careful. In the end if you are following good reloading procedures, load light and build up to what you want with either one.”
Can I use #41 small rifle primers in 204 Ruger reloads?
Yes. The #41’s have a harder cup and are very popular for reloaders who shoot primarily out of an AR15 platform. Most reloaders are able to use these interchangeably with the magnum small rifle primers without adjusting their load data, but you do your own testing if you choose to use the #41 small rifle primers in your 204 Ruger loads.
Berger Bullets Reloading Manual
Will small pistol primers work in 204 Ruger?
We have seen some reports that yes, many people have gotten small pistol primers to work in their 204 Ruger loads. Some report that they can even chronograph at faster speeds than with small rifle primers for that cartridge, though we haven’t verified this for ourselves yet. Your main problem with small pistol primers is the cup thickness and the free float firing pin in an AR style rifle. The free float firing pin makes contact with the next round’s primer when the new round is chambered. There isn’t enough force to set off a factory 204 Ruger round, but that may not be true if you have small pistol primers. Essentially, this could mean that you pull the trigger once and it could empty the whole magazine. At least that’s the theory. I’ve never actually seen it happen, though you can always get someone on a forum to claim that they’ve seen it happen. As with all reloading, if you decide to try this proceed with caution. Also, when test firing, load 1 in a magazine, then try with 2 in the magazine, then 4 or 5, before you try a full magazine. Every gun is different, so see how your gun will react before you just full send it with 204 Ruger reloads with small pistol primers. Even in bolt guns though, there’s also the risk of a primer puncture and putting too much pressure on that primer, so use smart reloading practices and load lighter than you otherwise would and build up if you decide to try this. It’s riskier to use a thinner primer like small pistol primer than it is to use a thicker primer, like an AR hard style primer.
Can I use small pistol magnum primers in 204 Ruger?
We’ve also gotten reports that yes, you can also use small pistol magnum primers to develop your loads. We also read a report that said for one manufacturer, they’re identical to the regular small rifle primers. Specifically, the CCI 550 Small Pistol Magnum primers and the CCI 400 Small Rifle Primers are the same size, with the same cup thickness. They’re also made from the same material and use the same explosive.
As always, do your own testing to confirm using safe load development practices.
https://apocalypticprepping.com/making-300-aac-blackout-brass-from-204 Ruger-5-56/
What Primers Do I Use?
I initially developed my 204 Ruger loads using regular small rifle primers. Now I either use #41 primers, or, more frequently, I just load all my .204 Ruger and 204 Ruger brass to .204 Ruger load levels.
Other Frequently Asked Primer Questions:
Will small rifle primers work in 204 Ruger reloads?
Yes, the 204 Ruger cartridge is made to take a small rifle primer. Some recommend an AR specific primer, with a thicker cup, but we haven’t ever had any issue with using regular small rifle primers in a 204 Ruger.
Can you use CCI 41 primers for 204 Ruger?
Yes. It loads about like a regular small rifle primer. It is a popular primer in AR type rifles. If you have light firing pin strikes, you may have problems with these, as they have a harder cup, but the 204 Ruger was originally designed to shoot this harder nato style primer.
Can you use CCI 450 Primers for 204 Ruger reloads?
Yes, you can. Small rifle magnum primers, like the CCI 450, will certainly work in the 204 Ruger cartridge. If you usually use a regular small rifle primer, we recommend not going straight to a max load after you make the switch. Work up loads safely like you otherwise would, but the magnum primer shouldn’t be an issue.
Where can I find 204 Ruger primers for sale?
I buy from Sportsman’s warehouse and several local shops by where I live.
CCI primers for 204 Ruger
CCI 450, 400, and 41 primers are all the commonly used cci primers used, and there is standard load data for each. Look at your specific load data and see if what it specifies.
What Winchester Primers should I use for 204 Ruger?
We recommend the WSR primer, or small rifle primers. They do have a thinner cup, at .020, so if you have a heavy striking free float firing pin, you may want to consider something like the CCI #41s.
Can you use CCI BR4 primers for 204 Ruger?
Yes. BR 4 primer are good to go. They’re a match grade primer, so they’re a more expensive option, especially if you’re just planning on using them for plinking, but they work. In fact, some prefer them for precision loads.
What Federal primers can I use for 204 Ruger?
- Federal 205
- Federal 205AR
- Federal 205M
- Federal small pistol and small pistol magnums at your discretion and at your own risk, but they fit and some have reported success.
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