I have a 686, which of course can fire .357's. I notice when reloading .38 special cases with target starting loads (using Unique or 700x and 125 grain heads) I have a lot of case capacity left. How hot of a .38 special load can you go before exceeding the pressure the 686 is designed for?

You can load them a lot hotter than annother .38 spl can handle. This is why its not a good idea to load magnum pressure loads in .38 spl cases. The chance of them winding up in a pistol that can not handle that level of pressure is likely.

Even though you may think that it will only be shot in magnum pistols because "you" know which ammo is over loaded a round can be picked up by friends or relatives or other people you wouldn't wish harm to.

If you stick to published load data for the 38 special you will have no worrys at all as the 357 mag is rated for higher pressures than the special. Its not a good idea to hot rod the special to magnum levels as the smaller case capacity of the special case can lead to increased pressure and the chance of the ammo finding its way into a revolver chambered for the special could lead to disaster!

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Stay safe people!

Like said above, load 38 Special cases to .38 Special pressures just in case they find their way into a .38 Special revolver. If you want to load .357 Magnum pressures use .357 Magnum brass.

To answer the original question, the current SAAMI pressure limits for the .357 Magnum is listed at 35,000 PSI. You can safely load to 35,000 PSI for anything you shoot in a M686 in good working condition without danger of harming the revolver. Just because you are using slightly shorter .38 Special brass doesn't change the SAAMI pressure limits for a caliber.

tg,

I have a suggestion for a revision of your question.

How much pressure can a M686 stand?

I think I understand your thought process but.....having more room in a cartridge is no reason to pack it full of powder. As ArchAngel has stated, there are pressure limits per cartridge.

Now, according to SAAMI specifications, the voluntary pressure limit that a 357Mag chamber should be able to withstand is 140% of maximum pressure. In CUP it's 1.4 * 45,000 = 63,000CUP They rounded up to 65,000CUP in their manual.
PSI is determined the same way, 35,000 * 1.4 = 49,000 rounded up to 50,500psi.

Suffice it to say that you don't want to push those limits and certainly not from a 38spl case. The 38spl revolver doesn't have to be built to withstand those pressures according to those same standards. Don't push it.

I can almost tell you what will happen if you load a 50,500psi load into some 38spl revolvers. A 357Mag may take several, I think the standard requires 10 rounds, loads of that magnitude, some of the junk 38spl revolvers around won't take half of that!

Be safe.

If there's anybody rooting around in my ammo, then they're stealing it. Whatever happens, happens.

Look out for the ones marked ".38/44 LOADS".

I recall Skeeter Skelton specifically, and probably more of the old writers, publishing .357 loads to be loaded in .38 special brass. I guess Skeeter figured that he would be the only one firing his particular ammo. I sort of agree, but I think it does open the door for a possible catastrophe. Probably not worth it.

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Georgia On My Mind

Skeeter's loads may have been readily identifiable too. From some of the things I have read he favored the 358156 bullet. It has two crimp grooves and seated in the one closest to the base of the bullet it would be virtually the same as being loaded in 357mag brass. I've never loaded that bullet but when loaded so it may not have chambered in a 38spl firearm. Notice I said "maybe" as I don't know for sure.

You can always use +P, or +P+ headstamped cases to denote which cases are loaded to higher pressures than normal, as well as clearly marking the container in which they are stored.

skeeter did it because he had alot of 38 cases and 357 brass was hard to come by, i dont think these where 357 mag loads, just hot 38 spec

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WILL WORK FOR AMMO!

Thanks for all of the responses. If my assumption is correct, then the reason the .357 case is slightly longer than the .38 case is to prevent the use of the hotter round in a .38 special revolver and not to gain extra case capacity. Point taken regarding the possibility of hot .38 loads finding their way to revolvers not designed to take the higher pressure.
But I also seem to be hearing that if properly labeled then loading .38 cases with hotter loads is acceptable. For example, if I were to use a .357 load chart and pick a starting load for a 125 grain head, the slightly small case capacity of the .38 would not be an issue. Why would I do this? Availability of cases and no need to reset my dies for the extra length of the .357 case.

If you cross section some .357 brass as well as some .38 special brass, you will find in general, that .357 brass is heavier in the web area, and partway up the sidewalls. That's why some who load warm loads in .38 brass use +P brass. It is usually thicker in that area.

I might rephrase it as "...the reason the .357 case is slightly longer than the .38 case is to gain extra case capacity (with increased velocity) while at the same time preventing its use in .38 Special revolvers."

This has been touched on here, and not long ago:

Keith .38/44 load

Loads such as these were worked up in the development stage of the .357 Magnum, so the concept has been around for a long time. In these "magnum days", we sometimes forget how effective some of the old cartridges can be when worked with in a careful and systematic way.

I have a 686; I also have J and K frames in .38 Special. Speaking for myself only, I would not be comfortable having .38 Special cases loaded to these high pressures; the consequences of one of them sneaking into one of the .38's would be severe.

The feasibility is there; the practicality may not be so certain. Good luck, and keep us posted.

Years ago I mistakenly loaded some .38 brass with 4.5 grains of Bullseye instead of 3.5 grains. In a .357, 4.5 grains is a stiff load but not a dangerous load and 3.5 grains of Bullseye is a stiff load for a .38. I touched one off in a S&W 586 and the recoil pushed the primer back into the firing pin hole causing me to have to dissemble my handgun and punch the primer out in order to get my cylinder open. If it had been a J or K frame, the revolver might not have survived. It just proved that the small difference in case size really makes a difference in the pressure of the round. My recommendation is to stay with the published charges for you and your revolver’s safety.

I think this would depend upon the powder. There are some powders, H-110/W-296 for example, that I would personally not attempt this with. Those powders require full house loads to function properly so even starting loads are stout. Adding to the potential problem it requires alot of case volume. Ex. Starting load for 357 Magnum 125 Gr. XTP JHP according to Hodgdon Online is 21.0 gr. of H110/W296. I'm not sure you could get 21 gr. of powder in a 38 special case and seat the bullet without compressing the powder. Even if you could you've put the powder in a much smaller area for the initial combustion which could cause a massive pressure spike. There's no way in hell I'd pull the trigger on 21 gr. of H110/W296 in a 38 Special case with any projectile on the end. I'm not that adveturesome anymore. Bottom line- this is one of those gray areas of reloading. There are some powders that should work fine if you use them at magnum loadings in 38 Special cases. There are some that could cause problems. Proceed with caution.

Just my two cents worth.

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Andy

I think Gun 4 Fun hit the nail on the head describing case construction. Not only is the .357 case longer but is also built heavier than the .38 Special case. The reason is to handle the higher pressure of .357 loads.
Strength of a firearm is not the only limiting factor on how much pressure a particular cartridge can be loaded to. Strength of the case must also be considered. Most reloaders have no means by which to measure pressure so loading .38 Special cases with powder charges exceeding published data is dicey at best and could be catastophic at worst. If using .357 loads use .357 brass. Cartridge cases are cheap when compared to the price of a gun......or a hand or eye.
Sam