First Serious .357mag Loads: Data & Some Questions

[roo_ster]

Howdy:

I have reloaded some rounds in the recent past, just to make sure I knew what I was doing (Whoo-hoo! They work & I didn't lose any limbs!).

I am starting to develop loads in a more serious, systematic manner.

First, a few questions:
1. Best way to shoot pistols & revolvers "off the bench," so as to test the loads, not my offhand technique.
The range I usually use has a waist-high table/bench/whatever. It is totally unsuitable for shooting from a seated position with any chair on the range or that I own (too high). I settled for steadying my off-hand against a metal pole, resting the meat of the outside of my right hand on the far lip/ridge of the table, and resting my forearms on the table.

2. Best way to get good results with a Chrony.
OK, other than not shooting the Chrony (Gamma Master model, FWIW). I think the addition of a torpedo level to my kit might help in aligning the chrony, myself, and the target. My first results were a bit...erratic, though I improved as I went.

Input Data:
Cartridge: .357mag
Weapon: S&W 686, 4" bbl
Brass: mixed, no nickel
Powder: Alliant 2400
Powder Weights:
13.5
14.0
14.5
15.0
15.3 (max found in search of several manuals)
Bullet: Rucker cast 158gr LSWC (available N Texas, DFW)
Primers: small pistol
Heavy roll crimp

Procedure for each powder weight:
1. Loaded 10 each
2. Shot 6-round group at 10 yards
3. Dry brass bore brush bbl & chambers between groups
4. Finished off all grouping-shots
5. Shot 4 over chrony

Analysis & Comments:
Even the hottest load (15.3) wasn't too bad in the area of muzzle blast & recoil. Some factory ammo is much more dramatic.

I wanted to evaluate each load by its 6-shot group size. Unfortunately, I could not get all 6 on paper for 13.5gr & 14.0gr. The factory ammo I had previously zeroed the 686 for made the POI quite low & off the paper for 1/6 shots for 13.5 & 14.0.

SD & ES for velocity improved as I went down in charge weight. I suspect this is because I started chrono-ing the heavies first & managed to whack the left front rod...twice. No damage other than a bent rod.

I settled for 5-shot group size as my figure of merit. Using the 5-shot group size, the best load was the max, 15.3. The second best was my starting load, 13.5.

The differences in 3-shot groups was pretty small (.18" separated largest/smallest 3-shot groups). The more shots, however, the more the group size diverged. (2.13" largest/smallest 5-shot groups).

Next Step
I didn't expect my best load to be the max. I had expected to find the best load and go +/- .2 gr each side in .1gr increments to zero in on the best load for my 686. Or, I would bridge the gap in .1gr increments between two loads if two adjacent loads (powder charge wise) happened to be to be best & second best.

I guess I'll decrement from 15.3 in .1gr steps: 15.3, 15.2, 15.1, 15.0, 14.9.

If the results are acceptable, I'll then work on a plinker-type load that is accurate at lower velocities.

The attached images are a table & chart of powder charge vs best X shots group vs group size as well as an image of my reloading log book entry. If you want the real deal, PM me & I'll shoot it to you (Open Office spreadsheet format).

Note: the skiny little thing in the "Attachments" box is my logbook entry

 

[Ben Shepherd]

Sounds like you've got the same results I did. In fact the "standard" 357 load that gets run on my dillon 650 en masse is a 158gr SWC in federal brass, 15.2gr of 2400, and a federal small magnum primer. VERY accurate in all of my pistols(around a dozen).

For a "premium" load I back the powder down to 14.8gr and use a 158gr. speer gold dot hollow point. Sickeningly accurate.

Speed-wise they run in the neighborhood of 1500fps depending on which gun.

Couple of suggestions:

1. Use good brass(I use ONLY starline, federal, or winchester) IMNSHO remington brass in this caliber is junk.
2. Use the same lot of brass for load development. This will bring your SD and ES numbers down dramatically, I promise.
3. Get a redding "profile crimp" die, then seat and crimp in seperate operations.

The above system nets me shot strings with ES numbers in the low 20's.

Your powder charge vs. your velocity should run roughly parallel to each other on a graph.

Mark you chambers somehow-if the same chamber always gives you that really fast or slow reading then you have a gun problem, not an ammo problem!!!


For shooting off the bench-sit on a chair and take enough sandbags(or whatever you have/use) to raise the gun up to eye level in a seated posistion. I use a case of shotshells or something similar, then set my sandbag on top of that. Works like a charm.

However you do it- The key is raising the gun to eye level, not hunching over to see the sights.

GOOD LUCK with your load development!!

 

[roo_ster]

Ben Shepherd:

Thanks for the tips.

 

[Ben Shepherd]

Couple other powders to try if you're inclined:

Blue dot- works very well for mid-range magnum work. A little cleaner than 2400, and a nice muzzle flash.

Lil' gun- amazing velocity potential

296- for the "full-house" stuff.

N110- VERY clean, low flash powder. Same velocity potential(roughly) as blue dot. Expensive though.

All of these powders show good accuacy for me.