I noticed that the Lyman reloading book sizes 38's at .358, and sizes 357mag at .357.

I'm shooting 38's at around 825 ft/sec.

Anyone know why, and if I already have a .357 sizer, am I really going to see a difference in accuracy vs. .358 sizing?

I am shooting cast RN from an old Ideal mold (311358 or 358311, can't remember, and don't have it in front of me).

Thanks.

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Eric

My Lyman cast bullet handbook shows both 38 Special and 357 sized to .357. Imagine my surprise at discovering this fact as I've been using 358 sized cast bullets for both for over 30 years. Try the 357 sizer, if your bore leads you probably need 358. Have you actually measured a sized bullet? Markings do not always match results.

In order to obtain best accuracy, without leading, from any caliber revolver, it's best to check the chamber diameters of the cylinder first. This is easily done with pin gauges. Your bullets will need to be sized to the chamber dimension for best overall results. Should, however, your chamber dimensions be smaller than the groove diameter of your barrel, the cylinder would have to be either exchanged, ideally, for one of just above bore size by not more than .002" or reamed to the proper dimensions. A revolver with undersize chambers will never shoot well, and give leading, as does the use of improperly sized bullets.

Thanks for the info guys.

I have been shooting bullets sized with a borrowed .358 sizer, and have had no probs, but recently gave the sizing die back to its owner.

Then, I saw they called for sizing the magnums .357, and thought, wow, maybe I can just use the .357 die and continue on.

I'll try a few, and see what happens in regards to leading. 99% of my shooting is double-action, and while accuracy is important, as long as it's reasonable, i'm fine.

It's not like $25 for another die would kill me, but i'm sure I could find another use for the money if the .357 works.

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Eric

Eric,
I have shot many a 38spl at those velocities from harder cast bullets than I use now sized to .357" without a lot of problems. My firearms and those bullets matched in size. My throats measured .357" so they worked fine.

Hardness is going to be something you will need to watch if those bullets are too small for your firearms. Make them somewhere in the 11BHN area and you might be fine.

What is the powder you are using? How long is the barrel?

Hope this helps.

Jim,
I will measure the cylinder throats (I was a machinist for 18 yrs, so it's no problem).

I'm loading a 158gr RN, straight wheelweights, 4.5 gr 231, 4" 581 or 10-8. I have no way of measuring hardness.

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Eric

In all my guns I usually size at least .001 over the cylinder throat or bore size. depends on which one is the biggest, I agree with Smith Crazy, the cylinder throat size is ther most important. However since I don't shoot max loads presure preoblem do not arise

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Semper FI

When I was a young fellow, just starting to handload, all the old timers would say to size .358" for Colts and .357" for S&Ws.

Who knows where they came up with that, but a lot of things the old timers said would work out pretty well. I have quite a few .38s and .357s, all S&Ws, and I prefer my cast bullets sized to .358" (a rebel! ), but I have never been upset by a batch that measures .357". I can't tell a lot of difference.

I have done more testing in 44 caliber and used diameters from .429" to .433" in my 29-2s. Again, can't tell a lot of difference, but I prefer .430" or even .431", if I can get them. But as long as the bullet is not too big for the cylinder's throat area, I am reasonably happy. When they get to be more than a couple thousandths smaller, then I start getting fidgety.

If what you are using gives good results, I would not worry over it, but if you want to experiment, there is no harm in that, either. No one has all the answers, and your guns may just happen to be ones that really prefer a certain size. You never know unless you try.

Someone previously posted, measure the revolver's cylinder throats for best accuracy; agreed.

Take a .358 slug and try to push it into the throats, ie, front openings of the cylinder.
If the fit is snug, then all is well. If too tight or loose, then You have to either size the slugs larger, or smaller; depending on what You've found.

Of course, using the proper tool to measure throats will produce superior results, but not everyone has those tools at their disposal. Hence the suggestion to use a .358 slug as a determining tool.

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It is....what it is!

Too large a dia. is prefered to too small. I have always sized lead bullets to .358" for 38sp or 357mag. You'll get better accuracy & less leading.

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NRA Cert. Inst. IDPA CSO

+1

Thanks for all the help. I measured the chambers on all of the revo's in question, a 64-3, 10-6, 10-8, and 581 no-dash. All were .357"

Going to try a hundred or so sized .357 and see how it goes. I'd also be interested to know how it affects speed. Will try to follow up in the next couple of weeks.

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Eric

+1 I agree with Fred (fredj338) I've done the same for many years.

I also feel that the majority of LEADING issues are from slugs that are TOO HARD as well as UNDERSIZED.

And I have to add......It's SCARY how much Fred and I AGREE 100% on a subject!!

FN in MT