1680 powder in .357??

[curioushooter]

Well, I didn't bother with the 1680 as it does seem to be too slow to work well. Maybe with a 200 grain or heavier bullet.

The good news: 300 MP appears to work very well...getting basically 100 FPS over a Lil'Gun with standard primers.

I worked up Lil-Gun from 13 to 15 grains (Hodgdon data) using 180 grain XTPHP and a Federal 200 primers (since they use a WSPM in the data). No pressure sings really at all. Case is sealing well. Relatively clean. Like I've observed with Lil'Gun it makes barrels very HOT. It maxed out at just under 1600 FPS from my 18.5" Remlin.

I worked up 300 MP with an extrapolated max load of 16.5 grains based off the 18.6 grain max load from Alliant for 158 grains and the 17.5 grain max load from Alliant for 170 grains. 16.5-16.4 appears to be a practical max load based on it being slightly compressed using starline brass sized in a Hornady die. 300 MP is not very compressible either. From 14.8-16.4/5 300 MP outclassed Lil'Gun in velocity, showed no hazardous pressure signs at all, and burned very cleanly. In fact, 300 MP, which usually leaves little yellow balls behind with the 158 grain loads showed NONE of this. Sealed as well as Lil'Gun did. Barrel did not get hot. Deviations were single digit (only did 3 shots at max though).

Theoretically this load should be fine in a L-frame or heavier framed revolver.

Maybe Hornady or Sierra will get a clue and test this load in their next edition (Alliant wont as Speer makes no 180 grain .357 bullet). I am becoming convinced that it is true that 300 MP doesn't need magnum primers. It seems to work better with Federal 100 than with anything else.

I also like how those very soft Federal 100 primers will show pressure signs earlier than about any other.

I also miked case webs and basically they were all the same after firing from starting loads to max.

[psweigle]

16.5 seems like a good educated guess for max with a 180gr bullet. Good to know the pressure signs seemed normal.

[dwtim]

I too was wondering about AA 1680. Thanks for all of this information.

I figured it would be okay with .357 180 grainers, but primarily in my .357 Max, and for lower velocity .223 Rem. Right now I'm using Accurate 4100 for pistol heavy loads all around. It didn't give me ignition problems like AA #9, and it doesn't leave unburned granules like AA 5744.

[curioushooter]

One of the things that I have realized is that that G2 in my Avatar has been my hunting pistol for a while. It is 357 Max and I use the 180 Grain XTP for hunting practicing mainly with the RCBS 358-180-SIL. The load that I use is 21.5 grains of Lil'Gun, which pushes the 180 grain xtp to 1800 FPS out of a 10" barrel. So, my 357 Mag rifle is basically equivalent, pushing the exact same bullet only 100 FPS slower.

[curioushooter]

Regarding 16.5 grains as a max with 300 mp using the 180 grain XTP. That is the newer kind which features one crimp groove forward for a short OAL case length that feeds without issue in my 1894. I came across some data from an editor's response in a 2012 issue of handloader that used 17.5 grains as a max with the older 180xtp crimped in the lower groove and fired from a Ruger (long cylinders). He didn't pressure test that load and I don't know how he got it, but he reported nothing alarming pressure wise. It seems that you will simply run out of space in a 357 mag with a normal bullet seating depth before you will go over pressure using 300 MP. I cannot even get the 22+ grains of Alliant's max with 125 grain weights to fit. By that way that is a smoking load for varmints/coyotes. A 125 grainer can be pushed to 2300 FPS. That basically puts it in the same league as 6.5 grendel or 30-30 out to 150 yards. Frankly where I live I think it may be better as it is ballistically inefficient and would hit the dirt on a flat open field missed shot sooner than a smaller bore round would.