The shiznit powder for velocity from your 358 Win

Jeff Olsen · Mar 3, 2007

I wanted to pass along an unconventional success I've had reloading for a fairly uncommon caliber, 358 Winchester. I built a 358 on a Model 7 action, using a 20" PacNor Supermatch barrel installed by them. Using the typical powders for 358 and 200-gn to 225-gn, IMR 4198 and 4895, I was never able to get satisfactory velocity even when I'd get into serious powder compression. And pressure signs. One of the fun things with a 358 is loading handgun bullets to insane speeds (for a handgun bullet) and RL-7 is the powder of choice for that. Out of desperation, after noting that not a lot of RL-7 gave great speeds with lighter bullets, I decided to see what it would do for me with 200's. I figured if nothing else, case capacity wouldn't be what stopped me, and I was right! I carefully ran up to book maximums for 200's, which gave the inadequate speeds as expected. But then, since my primers were absolutely round and there were no pressure signs whatsoever, I kept adding powder, finally ending up many grains over published maximums, but ALSO ending up at 2600 fps with 200's from a 20" barrel with round primers and looooong brass life.

I don't feel right publishing my load on a public forum, as it WAY over book maximums. I will be happy to provide it in a private email, however. I am at handwired@gmail.com.

So what does this mean? I have no idea. However, if you use a 358 and are looking for a science project, I humbly submit that it might be worth trying out RL7 and very carefully pushing the envelope.

I am essentially getting Whelen speeds from my little blacktail rifle, and I love it! Knocks deer down FAST. Now if Nosler would just make me that 200-gn .35 caliber AccuBond....

-jeff

Savage99 · Mar 4, 2007

The 358 Win is a sentimental favorite of mine. We use the 180 Speer these days and loaded it with IMR 4198 for about 2700 or so. Maybe a grain or so less in the 99's.

When RL 10 came out I worked up some loads over the chrono and more than 2700 was easy but the primers are not round.

RL 10 is a tiny bit faster than 3031 and is my powder of choice these days in the 358 Win with 200's as well.

358's.

Guest · Mar 10, 2007

If you're at all concerned with what that "way over" charge is doing, you should consider getting a mic, and checking the casehead expansion on second firing of some brass. Primers are one source of pressure information, but consider that we all think primers should look the same, regardless of what we're shooting them in. So a slightly flattened primer in my 30-30 is very likely at a significantly lower pressure than a slightly flattened primer in my .270Wby, but both primers look the same. If you throw in my .38Spl, then again, the primers are all slightly flattened, but I sincerely hope I am not generating Wby pressures in my little revolver!

So I would check with a mic and see what the expansion is, and if it is anything over about .0004, I'd consider backing out of that load a bit. You just never know when metal will fatigue enough to fail, because most all guns are proofed at the factory, which is significantly above SAAMI pressure, but the rifles all seem to still work.

Jeff Olsen · Mar 10, 2007

My brass life is extremely good with "the load" at 12-15 reloadings. I just retired a batch due to very small cracks in the neck in 2 cases out of 20... time to go. 14 reloads on that brass! My .358 brass starts out as new .308 Winchester brand brass, and I expand it up to .35 in one pass.

As far as primers I will say I've flattened pretty good in 7mm-08, which is the same case, but I hear you- I would love to know the exact pressure of the load!

I'll try some RL10 sometime; that sounds like a very good candidate too.

Ya'll should buy or build yourselves a .358! One really fun thing with 'em is to load 140-gn .38 Special or 157-gn .357 mag pistol bullets, and drive that at 2800-3000 fps. Waaaay outside their intended speeds. Those little hollowpoints are like little bombs with they hit something! I've got a load with the 140-gn bullet that holds 1.5 MOA at 100 yards. I keep waiting for a racoon to go after the chickens!

-jeff