Magnum Primers Change What... Exactly?

[BulletFactory]

My supplier is routinely out of stock on the winchester small pistol primers that I normally use, but they usually have the winchester magnums in stock.

I bought the magnums this time so I could shoot, but what exactly does this change, and how should I adjust the rounds to cope?

I'm loading a middle of the road charge of unique in a .40 S&W.

[Ole]

Doubt you'll notice much change in your application.

Keep in mind: The 40 S&W is a high pressure round and you should never substitute mag primers for regular primers in top loads.

[Jkallen83]

i use CCI primers. store was packed one day and i accidentally grabbed CCI magnum primers on accident.

after doing some reading, there dont seem to be much difference. i shot 200 magnums and 200 standard and could tell no difference. but for me in my 9mm's i could tell no difference.

some people told me to back the powder down a grain or two at first just to be sure.

[odfairfaxsub]

a grain or two would make a world of diff in pistols. he was prob talking about some rifle rounds.

[Old Caster]

With an American made primer, magnum means it will flash bigger but a Wolf Primer called magnum means thicker or stronger cup something along the order of CCI's military primers that are used to protect from slam fires in AR's.

[Harter66]

Lots of folks w/more brass case expirence than me. In shotguns however huge jumps can be expected . A winchester 209 was/is the lowest power w/the old Federal 209A being the hottest standard and the Win 209M being just hotter than that. The difference 209W to 209A load for load ran from 7-10 k LUP in any given load.

[fredj338]

IT depends. Use mid range data & swapping to a mag rpimer doesn't do much w/ SOME powders. Other powders sho more gain form a mag primers. So they are not plug & play, & it is wise to drop your load say 5% & work it back. A chronograph helps as all things being equal, velocity = pressure. I have seen significant jumps in vel, & assume pressure as well, when using a mag primer in 357sig loads w/ AA#9. I would think I am getting a more complete ignition of the ball powder by using the mag rpimer & getting higher pressure & vel.

[BulletFactory]

Since the mags are supposed to make a bigger flame, wouldnt this change the burn rate of the powder?

[ku4hx]

Since the mags are supposed to make a bigger flame, wouldnt this change the burn rate of the powder?

Burn rate is an inherent characteristic of the powder and can't be changed by simple means. If you could somehow remove the retardant in either whole or part, you could conceivably change the burn rate.

"Magnum" primers are generally constructed to have a higher (greater) "brisance". That being the case, they can cause more powder to be initially ignited than a "standard" primer would. That situation often raises pressure other things being equal. Thus the admonition to reduced powder charge if changing from "standard" to magnum" primers.

[303Guy]

That was a good explanation, ku4hx. Ummm .... just one point. The use of the term "brisance" comes to question (a bit off topic really). Brisance actually refers to the speed of a detonation, not the 'size' of the flame. Perhaps we should speak of the 'power' of a primer?

[Boerrancher]

I don't shoot max loads in anything any more, and I havn't noticed any difference in reg and mag primers in handguns. There is a noticeable difference in large rifle magnum primers and standard primers IF you are burning over around or over 60 grains of powder. It seems that around the 60 grain mark you get a more uniform ignition with magnum primers.

Best wishes,

Joe

[44man]

That was a good explanation, ku4hx. Ummm .... just one point. The use of the term "brisance" comes to question (a bit off topic really). Brisance actually refers to the speed of a detonation, not the 'size' of the flame. Perhaps we should speak of the 'power' of a primer?
Good point but I thought primers DO detonate. I don't think a mag primer has any more flame front then a standard but has more force to push the flame deeper into the powder charge.
Now I might be wrong but I see no more compound in a mag primer then any other. So do they increase brisance?
By igniting more powder at the start, pressures go up faster and allow a huge amount of powder to burn in a certain barrel length.
So I have to assume more brisance means more primer pressure and not so much more flame.
Flame quantity would depend on quantity of fuel.

[atr]

I do use mag primers in my .357 and IF I were going to load to the maximum load I would reduce the charge by 5% when using mag primers. However, I stopped loading (anything) to the maximum and with the .357 I have not noticed any difference between the mag primers and standard primers.

[felix]

Each primer lot is different. Case hardness/thickness, heat from ignition, and force from ignition. The ignition of a primer is so short in duration that it would be termed a detonation by definition. Magnum primer? What's that? I don't recognize that term as meaningful to me. Like Joe said, I prolly will use primers so designated on a trial basis for LONG CASES having more than about 60 grain capacity. Typically, Federal primers produce more heat and have the softest case; Winchester primers produce more force, giving a higher force/heat ratio. CCI more of a compromise, but with a harder case. ... felix

[Bob Krack]

I certainly do not know the validity of my opinion but I try to always use magnum primers in extreme reduced loads with the hope of igniting the powder furthest away from the primer. I am speaking or less than 4.5 grains of Bullseye in a large bottlenecked 30+ caliber cartridge or less than 7 grains of Unique in same.

I just know it works for me.

Bob

[hydraulic]

I get occasional failure to fire on the first strike from magnum primers. This happens with every cartridge I've loaded with magnum primers: M1 .30-06, 94 .30-30, Shiloh .45-70, .38 Special, 9mm. Probably have to hit 'em twice once or twice out of 25 rounds.

[oscarflytyer]

If you go from Std to Mag primers - Start over with your load workup, and drop at least 10%, and 15% would be better if you anywhere near top end/max with the std primers!

IME, a mag primer can quickly put an in spec load over the top of max in a hurry. I had this happen years ago when I changed from Std to Mag for my 300 Win Mag loads when I couldn't get Std. It was very scary!

Safety first!

[Frank46]

I have a sako 75 in '06. Federal brass, 55.5 IMR 4350, 165 grain ballistic tip and CCI 250? magnum primer. I have used this load in a few '06's and chronograph shows about 2800 fps. Also very consistent velocity readings. Yes, you aren't mistaken it is IMR 4350. I bought this some years back and only shoot this in my '06's. Great powder. Frank

[BulletFactory]

I figured that a mag primer would put more fire in a case faster, thus burning more of the powder more quickly. That would indicate that you would want to change powder to something that would burn slower.

[MikeS]

I have some 30-30 cartridges that I loaded a while back with 8gr of Trail Boss and the Lee 170gr FP boolit. After loading them I realized that I had used CCI magnum large rifle primers, so I haven't shot them yet. 8gr of Trail Boss in a 30-30 either is, or isn't a max load depending on who you ask. Using their 70% method of figuring out a load for TB, in the RP cases I was loading 10gr would be a max load, and 7gr a starting load. So should I be safe with the 8gr load with magnum primers? Or should I pull them?

[bobthenailer]

Ive only done this with one cartage and one load , 45 acp 5.0 gr of WSL 200 gr swc hg-68 style bullet. I orgionaly worked up this load with federal lp primers and was not a max load ! I then tried federal lpm primers because i had bought 25,000 for about $6.00 less a thousand than what primers were going for at the time . i checked accuracyat 25 yards from a rest with a red dot sight and for off hand shooting there was no real difference in accuracy , from the bench the std primers were a little more accurate than the mag primers, but i worked up the load with std primers to begin with.

[44man]

I have some 30-30 cartridges that I loaded a while back with 8gr of Trail Boss and the Lee 170gr FP boolit. After loading them I realized that I had used CCI magnum large rifle primers, so I haven't shot them yet. 8gr of Trail Boss in a 30-30 either is, or isn't a max load depending on who you ask. Using their 70% method of figuring out a load for TB, in the RP cases I was loading 10gr would be a max load, and 7gr a starting load. So should I be safe with the 8gr load with magnum primers? Or should I pull them?
Although a mag primer is not needed, you should be fine with your load. Two gr under max, I would shoot one and see. It is really not that drastic a change unlike shot shell primers.
The ONE reason I don't use a mag primer in the .44 is they tend to push out boolits before good powder burn. Depending on case tension, boolits can move different amounts and that changes case capacity with every shot. Larger cases can absorb the primer pressure before it reaches the boolit.
I even see it with the 45-70 revolver. It will fire fine with a Fed 150 but is way more accurate with the Fed 155 but if I go to a LR primer, accuracy goes to pot. Now shot from a rifle, the LR primer will work OK.

[Lloyd Smale]

mike you wont have any problem with that trail boss load and bullet factory you wont have a problem with your unique load either unless your using a load on the ragged edge of to much pressure allready

[44man]

Ive only done this with one cartage and one load , 45 acp 5.0 gr of WSL 200 gr swc hg-68 style bullet. I orgionaly worked up this load with federal lp primers and was not a max load ! I then tried federal lpm primers because i had bought 25,000 for about $6.00 less a thousand than what primers were going for at the time . i checked accuracyat 25 yards from a rest with a red dot sight and for off hand shooting there was no real difference in accuracy , from the bench the std primers were a little more accurate than the mag primers, but i worked up the load with std primers to begin with.
That holds true for the 1911 but we worked with a S&W revolver and could not get anything better then throwing rocks! [smilie=1:
I sat in the basement and stared at the case. I said to myself, the LP primer is too large. I made inserts to fit a SP primer, loaded them and reduced groups a tremendous amount. Then my friend that owned the ACP's found SP brass and they even shot better from his 1911.

[MikeS]

I have about 1500 45ACP cartridges made for small primers, and about 1000 made for large primers. From now on when I buy once fired brass, I'm going to try and stick with small primer brass, I don't really see the need for a large primer in such a small case. Of course at the moment all 2500 are loaded and ready to go, along with another 2000 aluminum cased Blazer cartridges that I replaced the original plated boolits with my cast lead ones, so I'm ready for the TSHTF day. :)

I noticed that the blazers are now boxer primed, unlike the original Blazer aluminum cases which were berdan primed so folks wouldn't reload them. They're still marked NR on the headstamp, but I might give it a try with a few, just to see how it goes. BTW, the blazer cases also use small primers, with any luck they'll be the new lead free primers, they leave the primer pocket much cleaner than regular primers!

[nanuk]

I have heard/read it all regarding primers

the best one I read though, was by someone whose wife worked in the primer manufacturing area of a company, and the explanation was thorough and comprehensive.

Just wish I could find that post.

[BulletFactory]

me too, what a tease.
:popcorn:

[W.R.Buchanan]

The only comment I want to make here is for all of those that may be lead to believe this is a good thing to do.

In any cartridge other than the .40S&W I'd say no big deal. Of all the cartridges this one is the least forgiving of minor errors in loading.

Too deep a bullet seat, or a smidge too much powder or the magnum primer with a smidge too much powder and you have got a problem.

The .40 S&W cartridge is a high pressure cartridge, and in a revolver that means you just need to hold on tighter, however in an auto pistol, it means more slide acceleration or recoil.

It also means possible case failure. Which is what happens when you push this case too hard. Also DO NOT load cases marked FC or FC10. They will blow up,,, got one sitting right here in front of me. This case is responsibile from most Glock blow ups.

If your charge is middle of the road then you will probably be all right, but I have to tell you, I would not make a habit of this when loading this cartridge. You only want magnum primers with certain powders that really need them for complete ignition. UNique is NOT one of those powders and the only clear result is an increase in pressure. How much I don't know, but I do know it is there.

It is not good loading practice.

Of all cartridges you can reload, you need to pay attention to the details on the .40 S&W the most!

Any other cartridge than this one and I would not have even commented.

Randy

[BulletFactory]

The .40 can be a really ornery female. I switched to HS-6, trying to beat a leading issue, didnt like how the Unique metered anyhow.

[Rocky Raab]

The only thing you can say with absolute certainty about swapping magnum and standard primers is that the change will result in:

Less, the same, or more pressure, and

Less, the same, or more velocity.

In almost any combination.

[SlippShodd]

I noticed that the blazers are now boxer primed, unlike the original Blazer aluminum cases which were berdan primed so folks wouldn't reload them. They're still marked NR on the headstamp, but I might give it a try with a few, just to see how it goes.

Sometimes they make it through resizing and/or belling without splitting and you can load them once. After that second firing 99.44% of them split. I've split a lot of cases in my 1911 over the years, but I don't feel the need to do it repeatedly on purpose.
I do however drill out the flash hole, load with wax and reprime for a perfectly acceptable mouse killer/garage load. They do hold up fine for that.

mike(c)