Home Forums Hunting & Shooting Ask The Gunwriters Magnum primers in standard loads?

Like everyone else, I'm watching my supply of reloading components. I have a surplus of large rifle magnum primers compared to standard large rifle primers, and I shoot standard cartridges a lot more than magnum cartridges. I think I have read that using magnum primers in standard cartridges is not a problem, but it's probably wise to reduce the powder charge somewhat, all else being equal.

What does the campfire intelligentsia say? Thanks!

I'd say do more and broader reading especially the readily available books from John Barsness. Components might be rare and expensive but knowledge is readily available and cheap at the price. Might start with say


By no means am I saying the problem is insoluble but I am certainly saying "not a problem" is a risk that ranks right up there with hold my beer and watch this.

What should a prudent handloader do any time he changes a component in a given reload? [not a trick question ]

southtexas,

In general, this is one of the "problems" where a chronograph is the handloader's best friend. When switching to a magnum rifle primer (or even to a certain extent anytime you switch primers) a chronograph will provide a pretty good guide to pressures, as long as every other component is the same.

Depending on the size of the case, drop the powder charge a grain or three, and see what muzzle velocity results. Then adjust the charge to about the same as the velocity using the standard primer.

Clark,

Thanks for the book recommendation! Rifle Troubleshooting and Handloading is now in its third printing, and keeps plodding along, a decade after it appeared....

John

Sounds like some sound advise here.

Not large rifle, because I have a lot of LRP, but I change standards to magnum pistol primers when I a shooting different types of powders. I use std. with W231,but get better accuracy using magnums in Universal. Of course adjusting powder amounts to suit.

Been using them in 243 and 30-06, just make sure you start your powder charge a few grains less while working up a load since mag primers are a little hotter.

Yes, there is a lot of good advice re LR magnum primers in place of LR standard primers for load development.

A topic I don't recall seeing though is minimum bullet weight (regardless of cartridge). Can the "hotter" LR magnum primer begin to propel a relatively light bullet prior to the powder beginning its burn? I am thinking non magnum cartridges like .223 REM, 243 WIN, or even something like a 125 grain bullet in .308 WIN.

While it’s a limited set of examples, the article on this subject by Brian Pearce in the 2015 Hodgdon annual provides some good illustrations of what can happen, and also some surprising ones where nothing much did. Since a couple applied directly to stuff I use, I perhaps got more out of it than others will. Worth seeking out.

I will have to check it out.

I have run a few experiments using Federal and CCI regular and magnum primers in 30-06 and 7.62x54R cartridges, measuring pressure and MV. I did not find any case where there was a significant difference.

Recently, I ran another test in 5.56x45 measuring only MV vs. CCI magnum and regular primers. There was no significant difference in MV. However, the standard primers started to plateau at lower charges than the magnum primers did.

That is not to say that there is no demon out there. I just haven't found where he lives.

I have never swapped from standard to magnum primers on a load already worked up, but I have gone the other way, subbing standard primers for magnums. I saw similar velocity in both cases, and slightly better groups with one and slightly worse groups with another. Sometimes primer choice seems to really matter with certain powders, but I have also found the opposite is true with other powders.

Going back 35 years with a bunch of 270’s with H4831 and 150 grainers everytime I substituted mag primers my groups got larger. Every time.

With RL26 powder mag primers did improve accuracy a tiny bit over standard primers in one 270. No difference in another.

My rule of thumb is I use magnums in loads greater than 75gr of powder. That said, every rifle is different. I can tell you I dropped DOWN to standard primers in my 338 (73gr of RL-19 and 210 TTSXs) and my groups for better.

Just another opinion without a lot of data to back it up..I ended up with a bunch of CCI Mag LR and some Fed 215 rifle primers for cheap a while back...I don't have any of the cartridges that one would normally associate with mag primers but who can be picky these days? I clang a LOT of steel and I cautiously started substituting mag for standard...in the 06 using IMR 4831...no velocity change, in the 6.5 Creed and H414 I gained about 30 fps, in the 6.5 Swede (29" bbl) with VV N160, I LOST 35 fps, in the 7.65 Belgian I again lost about 30 fps. WTH???
My half baked conclusion: in an efficient cartridge and somewhere around 90% volume of powder fill, mag primers don't mean a thing. Maybe they should be best utilized in overbore boomers.

Flintlock,
My experience has been with slow burning powder in 06 capacity cases mag vs standard primers don’t have a noticeable effect on velocity.

Large case capacity
Ball powders (I like H414)
Cold weather

Put those three ingredients together and I always use Fed 215
Or
WLRM

How does it affect my groups??? Not sure because I’ve never tested groups in sub 30f temps. Just rather eliminate a variable when hunting.

A few comments:

I started testing magnum vs. standard primers around 30 years ago. My first "experiment" involved the original mil-surp H4831 in the .30-06 with 180 and 200-grain bullets, a powder which was pretty bulky, especially with 200-grain Partitions. I found that 58.0 grains of H4831 with Federal 215s matched the velocity of 60.0 grains with CCI 200s--which helped the "problem" of getting enough powder in the case considerably.

This sort of deal doesn't always apply, but since then I have done a LOT more experimentation with various primers in cartridges from the .17 Hornet on up. Whether any difference occurs in velocity and accuracy depends on several factors--and not just the primer but the specific powder, including how much the powder charge fills the case. And the primer can also make a difference in how temperature resistant powders can be, whether or not they're advertised as temp-resistant.

Also, one of the advantages of being a gun writer is being able to consult with various people in the business, including long-experienced pressure-lab folks. Several of them provided great info on different primers, including stuff involving pressures, velocities and the consistency of both.

One was Ron Reiber, the recently retired head of the Hodgdon pressure-lab for several decades. I first got to know Ron around 30 years ago, when he contacted me about some problems with H335 I mentioned in an article. It turned out the difficulty was due to Hodgdon running out of the mil-surp powder they called H335, and having a new version produced--which turned out to burn somewhat faster.

Another good source of info from 1990s was the A-Square handloading manual, which included a chapter on how primers affect pressure, listing the piezo-electronic experiments they conducted. The results varied with the cartridge and powder, which could be expected, but they definitely occurred--and often the primer made a considerable difference.

Among other things I discovered was that there's also some overlap in "standard" and "magnum" primers, especially in large rifle primers--but also in some small-rifle primers. Not all "standard" primers result in the same pressures and velocities, and neither do all "magnum" primers.

As my research and experimenting continued I published several articles about all this, which also included how some brand/types of primers have changed over time. Most of this information eventually appeared in my Gun Gack books--but it involved a LOT more shooting (both mine and the results from ballistic labs) than trying a typical pair of of standard and magnum primers in a few cartridges.

John, I think we've discussed previously, but a good friend of mine who posts here and is an avid reloader related to me that a Federal engineer recommended magnum primers only if case capacity exceeded 80 grains. A few years ago I bought a bunch of primed 338 WM made by Federal so I pulled one of the primers and it was a 210.