In particular, I'm curious how their 180grain load does in a 4" K Frame.

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Aaron Terry

I would not loose any sleep over this issue Terry!! SAMMI lowered the 357 mag pressure from 46,000 CUP down to 35,000 CUP.. The factory loaded 357 mag is DEAD no matter who puts them together...

L.G.

FWIW, you can still do great with a 180-grainer out of a K-frame within SAAMI specs. I use Blue Dot and Lil' Gun and get wonderful results with mine, and I'm sure Tim Sundles does as well or better with his. K-frames are fine with 180-grainers (no forcing cone issues, though you may want to tighten some screws afterward), in my experience.

It was the J frame (scandium) and the K frames that caused the drops in pres!!! I'm sure sombody had a melt down in the past fireing the full load .357mags in their J frame .357 mag.. They'd go Bang real good back in the 80's..Not no more though, if you don't reload your own .357 mags you're shooting heavey +P38's in this new .357 mag factory ammo!!!! Its sad but true!!!!

L.G.

Check your units. SAAMI changed the old 46,000 CUP to 35,000 PSI, a change in units not in pressure. Factory published ballistics haven't changed in over 30 years when you realistically adjust the older velocities figures from the 8 or 10" solid chamber test barrels used at the time to 4" vented test barrels that simulate actual 4" revolver velocities more accurately.

I have load data from the last 35 years and with the same powders that are currently available some loads have increased a bit and some have decreased a bit but there's is no consistant move to lighter charges in the .357 mag. Over the years there's been small changes, sometimes increases and other times decreases. According to those that develop the data these changes have been due to changes in components over time mostly primers.

Steve, That is 46,000 PSI!! The CUP (copper units of PRESSURE) is how they get it!! CUP is still used to double check some data from the newer PIEZO transducer methods..

L.G.

PS Like I said if you don't reload,,, comercial .357 mag ammo is DEAD!!!!!!!!!

That is correct. When you examine the S&W ammo brochures from the year before the 1978 testing change, and the year after, you see that their 158 grain .357 round dropped from a claimed velocity of 1500 fps using "industry standard test equipment" (a quote from that brochure) to 1146 fps from a 6" Model 66 (the numbers stated in the next brochure). The drop in velocities I believe was mainly driven by the change to realistic testing methods. If in the early 1970's you thought your .357 sidearm was producing 1500 or 1450 fps with factory 158 grain ammo, you were being mislead by the industry.

I have a copy of NRA HANDBOOK #6. On page 77 is an article written by Al Barr of the H P White Company and Elmer Keath about 357 Magnum loads. They pressure tested these loads using an 8 3/8" Smith&Wesson barrel. All pressures were expressed in POUNDS.

The highest pressure load was a "commercial load". 158gr. velocity 1664fps 43,480 Pounds of pressure.
The highest pressure handload was only 32,000lbs. 1550fps 155gr Keath Ideal 358429 15gr 2400.
The book also says not to feed the Smith magnum a steady diet fo these heavy loads. I think this was done in HP White Labs

This NRA book was published June 1953