Large rifle primer question

When you change any major component, ALWAYS drop back to a lower load and work back up to your accuracy load within the necessary velocity for your purposes. In this case I would recommend going back to a known-good starting load.

You can do some leg work to best answer your own questions. Use grt and run the calculation between the two. Due to the nature of primers they represent about 5k of the total pressure. Figure out if your load is far enough off max to tolerate that change. Or calculate a rough reduction to compensate for the change. Because your Knowledge and ability is always unknown the standard practice of starting at start is always safe.

If you are going to start using magnum primers I would approach it just like you would work up any load. Start with a lower charge weight and then load in increments upwards. Inspect your brass after every shot and then settle on a charge weight that gives you the results you are looking for. Don't just assume that the magnum primers will give the same results as non magnum primers.

Depending on what we read your current load using H322 powder under a 150 grain bullet comes in a little under the maximum load suggested in the Speer 12th edition. The suggested max being 31 grains. With that in mind I would back off a little, no less than 27 grains and see what it gets you. If you are anywhere near Cleveland, Ohio shoot me a PM as I have plenty of large rifle standard primers.

Ron

It probably won't make enough difference to matter. But I'd play it safe and reduce my powder charge and work back up. Chances are good you'll find your old load is fine. But I'd not start there.

WHICH primer you developed that load with matters too. Not all standard large rifle primers are the same. Some are hotter than others and one manufacturer's large rifle primer may equal another manufacturer's magnum primer.

Since you are not at max, and only switching the primer, I’d drop back 1 grain and work back up towards where you were. Point being the primer makes little difference overall, like a small amount of the total pressure and you are only increasing it by a small percent of that. Dropping a grain might seem excessive, but any change in a component warrants backing off and working back up safely.

It could change your accuracy node, it can change your barrel harmonics, it could change nothing you may notice. Hopefully it will be minimal or not even noticeable.

@perryjosh, welcome to THR!
I’d definitely reduce the charge with the magnum primer, but can’t offer any help on a specific quantity. If it were me, I’d look up the load work up for this combo and reduce the charge to the next lower one I had used but that would be in the .3-.5gr range. Do you employ a chrono in your process? You could at least see where you are with Vavg. Good luck.

The standard when changing any component is lower the charge by 10% and work back up if necessary. Don’t go below published minimum.
Not to be offensive, but one can make all kinds of conveluted arguments for, and get any number of Internet opinions about, deviating from this standard, but the fact is, if you’re asking this question, you probably don’t have the expertise and experience to do so.

twarr1 said:

The standard when changing any component is lower the charge by 10% and work back up if necessary. Don’t go below published minimum.

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Just curious, where does that standard come from?

bullseye308 said:

It could change your accuracy node, it can change your barrel harmonics, it could change nothing you may notice.

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This is why I always advise going back to a known-good start load, one which predicts velocities in your gun's "sweet spot," and build up to accuracy, then worry about velocity. It isn't JUST about "pressure," it's about WHY you are handloading to begin with. If you're looking for accuracy, start low and check the accuracy nodes. If you're loading for hunting, look at the projectile's required velocity for terminal performance at the range you intend to hunt. If it's for plinking, look for the most economic load that still puts a bullet in a "target" under comfortable, enjoyable conditions without stressing you, your supplies, or your gun.
When you change a major component - gun (bore/rifling/chamber), projectile, powder, primer, or case - you can't just assume everything else will remain the same. Some powders don't react well to more/less brisance; some bullets need a certain velocity range to perform as advertised; some cases don't seat certain primers well... In my experience, changing cases has the least effect on the performance of a hunting load but if you read the journals of long-range rifle competitors, the case is the foundation of accuracy. Just depends on what you're after but taking the time to do a proper work-up is worth it. In my opinion...

perryjosh said:

Only reason I'm going to magnum primer is out of large rifle primers and these were free so figure id tinker with it.

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"Tinkering" is the best part.

perryjosh said:

You don't get expertise and experience without performing a task and practice hence why asking for advice on the matter from smarter and more experienced folks than me.

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Asking is better than destroying your gun, yourself, your life.
Problem comes from assuming that forum advice is from someone smarter and more experienced than you.

The "standard" is what has been taught for years (I was taught 50 years ago), when changing components, drop powder charge 10% and work up.
In your load, a 1 gr reduction would be where I would start.

The "shortages" of components has been more than just being without.

Good luck.

"Reloading 101", anytime there is change in components, do another load workup. No formula just start a new load. I have used magnum and rifle primers in pistol applications and always did a new workup. Many times the load I settled on is different from my "standard" load, even with the "Formula"...

Seedy Character said:

Problem comes from assuming that forum advice is from someone smarter and mote experienced than you.

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Yup. Times ten. Which is why the first piece of advice I give people is, "Don't do what I do."
I like published data but that's me. I also like researching and comparing published data. Again, that's me. I've given plenty of bad advice. Never on purpose.

Seedy Character said:

Problem comes from assuming that forum advice is from someone smarter and mote experienced than you.

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Agree. This is why I usually suggest my "Rule #1" to newer reloaders; I pay no attention to any load data I see on any forum or "pet loads" website, or hear from any gun counter clerk, good intended friend, range rat, or gunshop guru. I get 98% of my data from published manuals, and I had one squib in 1970 and no Kabooms, ever. There are legitimate websites for load data, but newer reloaders may not be able to spot dangerous data suggested in a forum...

mdi said:

Agree. This is why I usually suggest my "Rule #1" to newer reloaders; I pay no attention to any load data I see on any forum or "pet loads" website, or hear from any gun counter clerk, good intended friend, range rat, or gunshop guru. I get 98% of my data from published manuals, and I had one squib in 1970 and no Kabooms, ever. There are legitimate websites for load data, but newer reloaders may not be able to spot dangerous data suggested in a forum...

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Internet loads and pet loads can be useful if verified with actual manuals. Just running and gunning with stuff people post is a bad plan at best

The OP question is using published data. The problem arises in the thousands of possible combos between primer, powders and bullets.
No data will ever contain every possible combination.

Working through and understanding that extrapolation takes experience. Asking questions on a forum is sometimes necessary. Reading the books doesn't always make it clear.

As noted above; "a HP will be longer", "a HP will be shorter". Both can be true. Entirely dependent on the construction, bearing surface and nose of the bullet.

Observation, research, measure, compare and stay safe.

AJC1 said:

Internet loads and pet loads can be useful if verified with actual manuals. Just running and gunning with stuff people post is a bad plan at best

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I "short cut" the forum info and start directly with published manuals. But I started with books and while forums are very helpful, especially for newer reloaders, load data is just as well ignored. Once a newer reloaders' "BS Filter" has developed, forum load data can be a hint of what to check in a manual.

Of course this is just my experiences, but I have seen dangerous loads posted on a forum (I remember one, several years ago I saw a 357 Magnum load of Unique that was about 1 1/2 grain over max. The load stayed on the forum for a full day before the poster came back and apologized; "Fat fingers just hit the wrong number". I always wonder if some new reloader saw that load and figgered it was good, "it as on a good form".). Maybe I'm just a dinosaur 'cause I like books, but I have damaged no guns or parts of my body and now 40 years later, my go to is my Lyman 51st, Lyman Cast bullet handbook #4. Hornady, Nosler and Speer manuals. Depending on the bullet I use...

Had to fo some research on 2 different loads that just didn't seem right to me, I'm not sure where he, my friend got the data from, but both were way over. Dud proper load work up for those 2 rifles.

mdi said:

I "short cut" the forum info and start directly with published manuals. But I started with books and while forums are very helpful, especially for newer reloaders, load data is just as well ignored. Once a newer reloaders' "BS Filter" has developed, forum load data can be a hint of what to check in a manual.

Of course this is just my experiences, but I have seen dangerous loads posted on a forum (I remember one, several years ago I saw a 357 Magnum load of Unique that was about 1 1/2 grain over max. The load stayed on the forum for a full day before the poster came back and apologized; "Fat fingers just hit the wrong number". I always wonder if some new reloader saw that load and figgered it was good, "it as on a good form".). Maybe I'm just a dinosaur 'cause I like books, but I have damaged no guns or parts of my body and now 40 years later, my go to is my Lyman 51st, Lyman Cast bullet handbook #4. Hornady, Nosler and Speer manuals. Depending on the bullet I use...

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I posted a note in the Speer manual that called for 30-06 speeds out of a 308 that was not even achievable in their load tables. I have never seen, experience or herd of a problem using a start load from any manual. My normal blurb always includes consider using a starting load first. Now that precaution may be most useful in old guns where reloading might be the only option and rapid disassembly is more likely than say a new glock. The two layers of safety are knowledge and or a strict compliance with the manual. If you don't use or have one you better double down on the other.