357 Sig powder charge question

[faim1123]

I've just begun reloading for the 357 Sig and would appreciate some insight into powder charges. I'm using AA #9 powder and 125 gr, .355 dia Zero FMJs with Win SP primers. The load data indicates that the minimum charge should be 11.7 gr with a max of 13.0 for this weight bullet. I loaded several variations from 11.0 to 12.3 grains and tested them with my Sig P229 and I could not discern any major differences in accuracy. Obviously the flash and perceived recoil increased as the charge increased. My normal practice is to load as light a charge as I can that cycles the gun and results in sufficient accuracy. I figure the lighter charges are more economical and are easier on the gun. I'm not shooting competition so I don't need to make any sort of power factor.

However, my Sig P229 failed to reset the trigger on several occasions which has never happened when I shoot this pistol when it is configured as a .40 S&W, This behavior did not seem to be affected by the size of powder charge - meaning that it happened at 11 grains but it also happened at 12+.

So, here are my questions:

1) How is the charge related to the weight of the bullet? I ask because the minimum charge for the 125 grain bullet is 11.7 but for the 147 grain bullet it is only 9.4. I would have thought that the heavier bullet would have had a higher charge. If I can go lighter than the minimum without affecting function and accuracy that is what I'd like to do.

2) I read that 13 grains of AA9 was the 'magic load" for the 357Sig that supposedly produced the results closest to design performance. Is there any advantage for shooting at the max recommended charge?

3) What would be possible causes of the trigger not resetting properly?

Thanks, in advance.

[Justsomeguy]

As to the bullet weight thing... A heavier bullet for the caliber requires less powder because what you are really talking about is the maximum PRESSURE that the round and gun can handle. A heavier bullet, being harder to move, will generate more pressure per grain of powder than a lighter one. Thus, you use less powder with a heavier bullet to attain the same pressure levels that are in the range for the caliber.

Just as there are maximum pressure restrictions for a load, there are minimums. Going below a certain pressure limit for a powder and bullet combination can lead to a variety of problems like failures to feed or eject (not "running the gun"), very uneven powder burn (often shown by wide extreme spread (ES) and standard deviation (SD) figures, which leads to, at the minimum, a very dirty gun, or even (heaven forefend) a bullet stuck in the barrel, or in extreme instances, detonation, which means you might be wearing gun parts in your body somewhere. Powders are meant to operate in a pressure range. That range has maximums and minimums and straying outside those limits can, and usually will, lead to problems.

Edited December 8, 2013 by Justsomeguy

[Justsomeguy]

Oh... and as to the reset problem... There are a variety of things that can cause that too. I don't shoot a SIG anymore, but when I did I never had that problem, but several parts have to return to "zero" on every firing cycle in order for the trigger to reset. It is possible that gunk has worked its way into some places that are more sensitive to this and is preventing one or more parts from returning to where they are supposed to be. Also, a weak or broken trigger return spring, or one that has not been put into the assembly correctly, can cause this. If you are unfamiliar with the inner workings of your pistol, then I would recommend that you either write to or call SIG customer service and see what they have to say or take the gun to a competent gunsmith for evaluation. First... do a thorough cleaning, preferably with a full takedown of the upper and make sure nothing is interfering with the specified operation of the parts. Get some spray "carburetor cleaner" or some such and take the gun outside where it is over some old newspapers or other disposable drip surface, and spray down all the internals of the frame to insure that the firing residue that may have accumulated is completely washed out, followed by a VERY light oiling of the critical parts. You would be surprised how many guns have been rendered inoperable by too much oil which attracts goo in places that are not tolerant of it.

[jcc7x7]

I shoot the so called perfect load out of mine 13.0 grains of AA9. this is my carry/defense load with a Speer Gold dot 125gr bullet.

Practice and fun load is with unique, only because I have a ton of the stuff so I'm always looking for a place to use it up.

The But is both loads cycle my gun and reset the trigger.

trigger not resetting is due to the dis-connector or the trigger bar not being pushed down. I would bring both bbl's to the range and exchange them on /off to make sure it is happening at the same time/range trip. If it is then the gun and both bbls should probably go back to SIG.

If not then its probably crud that needs to be cleaned out of frame to allow parts to move more freely. But I've shot mine awfully dirty and it seems to always reset.

Good Fortune

[faim1123]

Thanks to all for your answers. Most helpful.