Can you substitute magnum primers for regular primers?

[bigjeepman]

I am in pretty good shape as far as primers go but I have a question for you. I have been reloading for many years but have always gone by the book ... never going over listed max loads as I have always seemed to find that sweet spot before I got there. So I am guessing almost all of my loads for .38 spl, .357 mag, .45 acp, .45 colt, 7mm-08, .308, and .444 Marlin for examples are in the range of 85% to 90% of max loads. My 45/70 loads for my Marlin 1895GS and my Sharps rifle are only 1200-1400 fps so those are not even close.

Here is the question ... can I use (if I have to at some point in the future) substitute magnum primers for regular primers and not have problems? Another example ... shooting a Sierra 168gr HPBT over 44.0gr of Varget in my 10FP rifle? Another example ... shooting a Nosler Accubond 140gr over 41.6gr of Varget in my Tikka T3?

The reason I ask is because about 25% of my primer stock are magnum primers. It will take some doing to get down to that but it could happen as the future is fairly uncertain about availability with reloading supplies. I am thinking I might have to back off a grain or two of powder but I am uncertain if it is necessary.

What do you think?

[celltech]

I have seen reloading data that suggests a magnum rifle primer raises the initial pressure by ~1600 psi. That would equate to ~.4 grains of powder in something like a 6.5 Creed load...so not a giant difference.

[Robinhood]

Short answer, yes. A small reduction in charge weight is suggested as Celltech stated.

[Stumpkiller]

Agree with above. But I don't know the powder reduction you'd need. I'd drop back 5%. That's the "safe" minimum whenever you change a component . . . that in practice I'd wager few of us practice.

[bigjeepman]

What I am understanding is that if I ever have to use magnum primers that did not call for it, start load development over again by reducing powder charge and work my way back up. Hodgdon's load data for the .308 Win 168gr bullet and Varget powder ... minimum 41.0gr ... maximum 45.0gr. So at my 44.0gr load, I would be "probably" be okay but would be very wise to back off to say 43.0gr and move forward slowly in say .2gr increments.

This makes a lot of sense now.

[stanekjm]

Back a few years ago when we had a similar crunch on everything related to guns/ammo/reloading, I came across a small lot of magnum small pistol primers. I reloaded a few hundred 115 and 124 gr 9mm cartridges with them. Never saw any pressure signs. Granted I was staying at the minimum according to my Speer manual (which tends to be a little more liberal) If they are all you can find, use em and like the others have said, reduce your max charge and watch for flat primers or if you are really over pressure cratered or pierced primers.

[CFJunkie]

I have used magnum primers in hunting rifles to compensate for really cold weather effects that cause velocity to drop off.
With non-extreme powders, velocities drop in cold weather by about 1 fps per deg F.

I tested my M70 .270 with regular and magnum primers on identical loads at 29 degrees F.
Magnum primers increased muzzle velocity by 12 to 16 fps.
Not as much change as I thought they would provide, but it got back about half of what the powder lost to temperature drop.

I wouldn't recommend using magnums in hot weather though.

[geezerhood]

Switching to a magnum primer can also REDUCE the pressure of some loads.

[bigedp51]

Are Small Pistol Magnum & Small Rifle Primers Safe in 9mm?




CHOOSING THE RIGHT PRIMER - A PRIMER ON PRIMERS
http://www.sksboards.com/smf/index.php?topic=56422.0

CUP THICKNESS

"In rifle cartridges, the 6-1/2 small rifle primer should not be used in the 17 Remington, 222 Remington or the 223 Remington. The 7-1/2 BR is the proper small rifle primer for these rounds."
CCI/Speer Technical Services says: "The CCI 400 primer does have a thinner cup bottom than CCI 450, #41 or BR4 primers... [with] the CCI #41 primer... there is more 'distance' between the tip of the anvil and the bottom of the cup." so that is their AR15 recommendation, although it seems like there are no complaints with using the BR4 and 450 primers by AR15 shooters and reloaders, in general. The #41 just gives you a little more safety margin for free-floating firing pins and would be the best choice for commercial reloaders who have no control over the rifles their .223 ammo is used in.

Small Rifle Standard

CCI 400 -thin .020" cup, not recommended for AR15 use by CCI/Speer. Good for .22 Hornet, .30 Carbine. See Note 1 at the bottom of the page

Small Handgun Magnum .017" cup thickness

CCI 550See Note 1 at the bottom of page

NOTE 1: According to Speer/CCI Technical Services - Both the CCI 550 Small Pistol Magnum and CCI 400 Small Rifle primers are identical in size. Both primers use the same cup metal and share the same cup thickness. Both primers use the same primer compound formula and same amount of primer compound. They can be used interchangeably.

[bigjeepman]

Switching to a magnum primer can also REDUCE the pressure of some loads.

Could you give an example or a source for this? I cannot imagine that being the case but it could very well be.

[JeepsAndGuns]

It can change it very little on some cartridges, and a little bit more in others. However unless you are at or near the max load, it should not be much of a issue.
The best thing you could do is load some up yourself and try them. I would reduce your load a little and work back up. That way you will know what and how much you need to change your load when/if you need/want to change to the mag primers.

I also did a test myself on pistol rounds and did not see a huge difference.
https://www.ar15.com/forums/armory/S...ts-/42-518085/

[bigjeepman]

It can change it very little on some cartridges, and a little bit more in others. However unless you are at or near the max load, it should not be much of a issue.
The best thing you could do is load some up yourself and try them. I would reduce your load a little and work back up. That way you will know what and how much you need to change your load when/if you need/want to change to the mag primers.

I also did a test myself on pistol rounds and did not see a huge difference.
https://www.ar15.com/forums/armory/S...ts-/42-518085/

That was interesting data ... thank you for the link.

[JeepsAndGuns]

I have been wanting to do the same thing with large pistol primers, regular vs mag, vs large rifle just like I did above with the small pistol. However I just have not had the time to do so, I have been very busy lately.
I also have a 1000+ large rifle mag primers and want to run some across the chrono back to back with regular primers and see how much difference there is. But same as above, I just have not had the time.

[darkker]

The answer is, that it depends.

I've been pressure testing lots of different things in the past few years, and most of what people "know to be true" really isn't with much regular consistency.

So the application, and the details matter in a big way. If you want generality and simplicity in your life, then any time you change anything, return to starting loads and re-develop your loads.
If you can live with details and conversation, it probably doesn't matter as much as you've been told.

I don't fox with basic priming compound, so that may make a difference. I've only tested regular and DDNP compounds.

https://photos.app.goo.gl/8PWTvMgxvH9Dbjaf6
https://photos.app.goo.gl/n3jnC3d6TZmRgT5d8

Now the "noise" aside, I've done this with every brand of regular compound primers. In a 308-ish sized case, it doesn't matter. It didn't matter in my 204, however I haven't tested pistols.

Cheers

[rerun5]

I had the same question several years ago after buying a box of standard LRP's and upon opening finding I had 1000 magnum LRP's. So I asked this question about rifle primers and was given enough positive answers to test them in all of my LRP rifles. I reduced the start charge weight by .5 grains and worked up and I ended up back at the start charge. I didn't do this for pistols but I understand it is the same principle. I wouldn't have found this out if they would let us return unopened primers, but that isn't allowed.

[geezerhood]

Could you give an example or a source for this? I cannot imagine that being the case but it could very well be.

I found quite a few places on the web that talk about reduced velocity when switching to a magnum primer for the same load. Reduced velocity almost always means reduced pressure, all other things being exactly the same. I remember reading at least one article that had some pressure testing with it, but I don't remember the search terms I used or where it was. One theory, not proven is that the extra push from a magnum primer causes the bullet to "jump" into the throat before the powder gets burning, thereby increasing the volume and reducing the pressure. Sounds a bit off but perhaps it is true. Multiple individuals have experienced reduced pressure signs and reduced velocity when substituting a magnum primer for a standard, so I pretty much bought into it until I see something different. That doesn't mean you can't get an increase in pressure, but that is not always the case.

https://www.google.com/search?client...+magnum+primer

[Woopig]

My Speer book substitutes magnum for standard on ball powders.(rifle) I do on .357 mag reduced charge. No issues at all.

[Idaho]

I've been doing load development for a 25-06 to use on chucks. Most accurate bullets have been the Berger VLDs. The powder/primer combination that delivers SD in the single digits, like 2fps, is RL-23 over CCI-200 primers. I have very few of the CCI-200 but have a brick of the CCI-250s so I've tried them and the results are not good. Same powder will not give low SD with the 250 primers!?!? I've tried to vary the powder charge and seating depth with no joy. So, yes, Magnum primers will make a difference in how your loads shoot. With the right powder I'm sure they will be fine. I use the CCI-450 primers in one of my 223s and get excellent results from them. Load some up and run them over a chronograph to verify and compare with your standard loads and primers. Who knows? You may get lucky.