357 Primers - SP vs SPM

[HNSB]

I am putting together some hunting loads for my 357. I am using a Lee C358-158-SWC mold. With my alloy, and gas checks applied, my finished boolit weight is about 161-162 grains.

I have a few questions:

1. Is it OK to use 158 grain load data for these boolits as long as I don't push it all the way to max? To go heavier, I have to go up to 180 grain boolits to find load data for the powders I want to use (2400 and W296).

2. How much difference is there between using SP primers and SPM primers? I have some load data for both with a 158 grain cast. I would like to know if I am better off one way or the other. I have plenty of both primers... Lee says use SP in general, Lyman says use SPM in general...

3. Looking at the data in modern reloading and in Lymans Cast Bullet Handbook, both manuals say to not load reduced loads with 296, and thus only list a max load. Here's the problem:
(Both loads are for a 158 grain cast bullet)

Lee:
SP primer w/ 14.5 grains of 296.

Lyman:
SP mag primer w/ 18.0 grains of 296.

Doesn't that seem like a substantial difference? Shouldn't the load with the mag primer generate more pressure, and thus use less powder? Or, am I backwards on that?

4. Lee says a max load for 2400 is 15.3 grains. That's substantially more than what I see other people using for 158 grain cast... Is there any reason for this? The max load I worked up tonight was 14.9 grains of 2400 and I felt that that was on the high side... I haven't been to the range yet, but I have several loads of 2400 under that. I will be watching for pressure signs as I go up.

5. Does anyone have a pet load for the C358-158-SWC? I plan on using this for hunting whitetails this fall...

Thanks!

[runfiverun]

1 yes
2 i use regular
3 not sure i don't use 296
and i have never seen lee reommend a primer.
i use herco in the 357 and 7-8 grs is plenty for what i need.
15 grs 2400 seems quite a bit in the 357 iirc i used about 12-13 and was happy.
15 is a stout load in the 44-40 with a 200.
and only 16 in my 41, pretty sure i can go up a tad but it is a handfull.

[2ndAmendmentNut]

1) Yes, as long as Max loads are approached with caution (which is how they should be approached anyway, if at all).

2) Not sure how much, but I know for a fact there is a difference. I have used both. Ball powders such as 2400, W296, AA#9, H110, etc in general are more difficult to ignite. If excessive amounts of unburned powder are left behind using a SP switch to a SPM.

3) 296 needs to fill the case or even be compressed for reliable ignition, this is also true for many other popular ball powders for the 357. Reduced loads can cause squibs, and inconsistent velocities. Most load manuals will vary a little in there loads, I always start with the one that is the most cautious and only move on to the higher data if I am having issues with accuracy.

4) Max loads will be in theory the fastest, but rarely the most accurate. Using less then max loads are easier on the guns, brass, and shooter.

5) Sorry, I prefer a 170gr SWC from a Lyman 358429 mould on top of 15.1gr of H110. Not that your boolit is a bad choice, I just personally like the 170gr SWC better (no gas check to fool with).

Oh, and welcome to the forum.

[Echo]

I have loaded 15 grains of 2400 behind a 158-160 gr boolit for many years. Stout, somewhat flattened primers, but no problems in my BH. And I always use SPM primers, no matter what powder.

[Whitespider]

HNSB,
All very good questions, clear, concise, specific. I just wish the answers could be as clear for you.

1) - A reloading book is not a bible, it is merely a guide. It is impossible for you to duplicate all the conditions used during development of the data. Even if you use the same model gun, mold number, and components the differences in bore & chamber dimensions, cylinder gap, component lots, alloy, lube, bullet hardness, plus a multitude of others will all affect the results. This all requires that you be cautious, start low, work up slow and be ever vigilant in spotting problems. Yes, the 158-grain starting load data you reference should be safe as a starting point, maximum loads are maximum only for the conditions used to develop the data and have no bearing on your gun and load. It is up to you to determine what is maximum in your gun under the conditions it will be used. With revolvers, I normally prefer to see the fired cases fall from clean chambers under their own weight, or sometimes in the case of maximum magnum loads in strong(er) revolvers, with just the slightest nudge from the extractor. But that’s not fool-proof, as a rough chamber wall, oil in the chamber, the brass itself or even a tiny piece of crud can affect extraction; again, you must determine what constitutes a safe load, and to error on the conservative side is the best way to go.

2) - The “Magnum” moniker on primers is just silliness. Just because it’s labeled “Magnum” doesn’t automatically make it “hotter” than all “standard” primers, it just means that it’s “hotter” than the “standard” primer of the same brand! A Brand-X “standard” primer can easily be “hotter” than a Brand-Z “magnum” primer, and that’s a simple fact, I don’t care what anyone says! Add in the lot-to-lot variances and primers can easily swap places on the “hotness” scale. Choose, or use, the primer that produces the most consistent ballistics with your load and gun, regardless of its “magnum” or “non-magnum” designation.

3) - The W296 “Do Not Reduce” comes from the original recommendations from Olin/Winchester. Some manuals actually show starting loads for 296, some do not. Checking a few more data sources may help you get a feel for a good starting point would be. Probably the safest course would be to stay away from 296 until you gain a bit more experience with full-house magnum loads with your gun/boolit combination. Besides (just my opinion), I find 296 better suited to heavy cast boolits, 170-grains+ in the .357 Magnum.

4) - See the answer to question #1. Do you own a chronograph? How about loading to a targeted velocity level instead of a maximum load?

5) - From wimpy to almost wham-o, I use W231 with a Federal “standard” primer for most .357 loads using 140-160 grain boolits. W231 will easily drive a 150-160 grain cast boolit to 1200 fps from most 4-inch revolvers with excellent ballistic uniformity.

[HNSB]

Thanks for the answers. I do have a chronograph, and with most loads I look for consistent velocities that are within the expected range of that cartridge. I just want to make sure that my test loads are safe. I am willing to pitch some if the pressure on a lesser load seems too high, but it's always sad to waste components.

I might try some test loads with 231 as well. I have plenty of it laying around.


These are my first test loads using cast boolits for my 357. After applying checks and sizing the boolits pass through the chamber throats with gentle finger pressure. The chambers are slightly larger than the barrel. From everything I have read this is ideal... I am excited!

[jdgabbard]

I've also wondered the same question from time to time. The suggestion that was made to me, was that if it is a powder that prefer magnum primers, ie ball powders, then use magnums. If it is a powder such as unique ect. then use standard primers.

Some have said that magnum primers have a metallic dust in them that spark, helping ignition. I don't know about that, but using them with powders that seem to like more light isn't a bad idea.