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Rifle Primer question: mag vs reg?

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WestTN2288

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Just like title says, does anybody see a big difference in switching from magnum to standard SR primers in loads like hot 5.56 and 6 arc? Would it make a big difference in the accuracy/performance of loads? Some loads I am running now, show some signs of primer flattening on SR mag primers.

Mostly because I am having trouble finding SR magnum, but surely somebody here just knows the answer or can at least point me a couple of steps on the right direction.
 
The procedure to follow is : any time you change a component you need to reload at the lowest recommended level and build back to your desired or best available accuracy.

If you change from SR regular to SRM primers you should have started at the very low end of the powder charge scale.

Flattened primers are an indication of over-pressure. The issue is worthy of research on your part just to insure you know the exact cause. For example, if the only difference in 223 loads is the Magnum primer and you have flat primers and did not have before, we can confidently blame the magnum primer.

Have you noticed any increase in recoil? Muzzle blast? Sticky bolt lift or stovepipes or ejecting brass to the next county? Look at the SRM fired brass neck for splitting. The SRM fired brass primer pocket compared to a fired SR primer pocket from same rifle you see a carbon residue difference?

My experience says you will see a difference in POI. You need to watch for any signs of overpressure beyond flattened primers. Be careful as you approach the max load.
 
My stuff runs about 1-1.5grs different on regular vs magnum sparklers. A chrono would be the only real way to see where you are at for velocity, es, sd, etc


As for flattened primers, I wouldn't put much into that. If you are oversizing your brass and creating excess headspace you will see flattened primers. Primers in general are not a good way to read pressure. Flat primers can come from excess headpsace, cratered primers can come from excess space in the firing pin hole on the bolt.

Primal rights has a great article on why primers aren't a great way to read pressure. I would post a link but every time I post a link my posts are set to invisible for moderator review. The article is Understanding Pressure
 
The primer flattening doesn't bother me much, I kind of expect it from the loads I have been running. Every other signal from the brass says I'm okay. The point of impact/velocity information was what I guess I was really asking.

I feel like I can find a decent amount of info about going from standard to magnum, but not nearly as much about going the other way.
 
I have run CCI 450 in all my AR's with no issues, but I worked up my loads with those primers. I wouldn't just swap primers without going through load development again.
 
CCI 450s are available at several places right now, as well as 41s. Midsouth, Natchez, etc. I think that N GA Reloading had them the other day, too.

SR Mags have a harder cup for usage in ARs. Theory is that the floating firing pin could cause a slam fire with more sensitive primer cups of standard primers. It's never happened to me.

Some loads will shoot better with one primer or the other. Only way to find out is to try them, but start low and work up
 
Okay, while on this subject I have a question. I have used regular small rifle primers in 6.5 Grendel with good enough results. I do have 20 rounds of Lapua brass 6.5 Creedmoor that must use small rifle primers. In the Creedmoor case do you think small rifle Magnum primers would be more appropriate?
 
rifle02 said:
Okay, while on this subject I have a question. I have used regular small rifle primers in 6.5 Grendel with good enough results. I do have 20 rounds of Lapua brass 6.5 Creedmoor that must use small rifle primers. In the Creedmoor case do you think small rifle Magnum primers would be more appropriate?
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I'm about to embark on the road to using some Lapua srp pocket brass for some test loads in my 6.5 CM as well, and my thinking has led me to choose SRM primers also. I've used Hornady and Starline LRP cases with no issues, but I have heard from some that there is a potential for less fire thru the flash hole with the SRP cases, so that's the route I'm taking from the start.
 
rifle02 said:
Okay, while on this subject I have a question. I have used regular small rifle primers in 6.5 Grendel with good enough results. I do have 20 rounds of Lapua brass 6.5 Creedmoor that must use small rifle primers. In the Creedmoor case do you think small rifle Magnum primers would be more appropriate?
Click to expand...
I don't know why, and will test it myself, but the Grendel seems to like magnum primers
 
WestTN2288 said:
thank you all for the responses. Sounds like I'm starting a new set of loads.

Also, I need a reason to come to the other side of the state. I can't seem to find them anywhere over here…
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Looks like most of the online places have them available pretty regularly now. The price is still more than I'm going to pay, but the availability tells me the price will be coming down.

I recently got some at our local sportsman warehouse for $8.25 for 150. But they had a two pack limit. That's $55 per thousand, (provided you have six other people with you 🤣) , so the prices appear to be coming down.
 
I use Cci 450's to load .308 in the SRP Palma brass. You will get more consistent speeds than with standard primers especially in colder weather.
 
fairchaser said:
I use Cci 450's to load .308 in the SRP Palma brass. You will get more consistent speeds than with standard primers especially in colder weather.
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I had to switch to Fed 215 Mag primers in my 300 WinMag using H1000. I had ever so slight hangfires at the range when it got cold. Slight, and only I could tell behind the rifle, but definitely a slight delay in firing.
 

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