357 AA#9 XTP Load Confusion

[BBDartCA]

What are people opinions on selecting a starting load for the above with a 158g XTP Hornady with 6" barrel. Notice the great spread in load weight from the below published data.

Start - Max
9.7 11.5 Hornady data in current "Loadbook"
13.5 15.0 Accurate data in current Loadbook
12.4 13.8 Data currently on Accurate web site
14.2 15.8 From 1992 Accurate handloader book, 5th edition
13.5 Best load per 8/2011 issue of Handloader mag in a review of this powder

I would say starting at 12.4g would be the best bet and use current Accurate data as a guide. But anybody have an idea why the Hornady loads is so much lighter than the others? Similar situation looking at some of the other powders Hornady gives data for. Have emails into them with not response.

 

[CZ57]

Does Hornady recommend a Magnum primer?

 

[BBDartCA]

They do not indicate what primer to use.

 

[rg1]

Accurate manual #1 used CCI 500 standard primers in their data for .357 Magnum. Later info from Accurate used a magnum primer. I load 13.0 grains of AA#9 with CCI 500 primers, 158gr. XTP's and it's very accurate in my 6" revolver and my Marlin rifle. Accurate Arms data seems to be reliable. Just from my experience I'd go with the start at 12.4 and consider max at 13.8 grains.

 

[Steve C]

I've generally found that AA9 produces a load very close to what you would have with a 1.0 gr heavier charge of 2400. I've chrono'd 12.3 grs of AA9 behind a 158gr LSWC bullet at 1,268 fps from a 4" S&W 66. I'd expect a jacketed bullet would knock off around 100 fps in velocity so the current recommendations from Accurate of 12.4 gr (start) and work up to 13.8 gr (max) would be the appropriate range of data to use.

 

[rg1]

Hornady's latest 8th Edition manual uses Winchester Small Pistol Magnum primers in their tests. Test used a 8" barreled revolver with Hornady cases. Hornady 8th lists 9.7 grains of AA#9 for 1000 fps and a maximum listed 11.5 grains at 1200 fps.

 

[Marlin 45 carbine]

I've loaded 14.5 gr of #9 under the 158gr jhp for my 4" GP100 with great groups but unfortunately a tremendous fireball. I'd be intersted in seeing how this load would do in a carbine but as of now I don't have one.

 

[mdi]

When I use Hornady bullets, I use Hornady's reloading manual. Start with the Hornady data and go up from there. Many reasons for differences in data from one manual to another, but Hornady tested with their XTP bullets and test equipment...

 

[noylj]

What part of "start with the smallest minimum charge?"
IF your revolver is like the barrel used by Hornady, you would be starting ABOVE the maximum for your barrel.
Safety first. Start with the smallest starting load you can find.

 

[41 Mag]

Typically I consult a minimum of 4 sources of data including the bullet and powder manufacturers. If there is a big spread in the data I take all of the smallest charges, and average them and start there. I have not found any issues in 30 something years of doing so. Just the way I go about it, don't make it right or wrong. YMMV

 

[wleoff]

Call Hornady and ask them. I did that recently about their FTX bullets and they transferred me to a very helpful gent who clarified my mixup.

 

[Clark]

CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.

From my notes about loading an S&W 60 I reamed out from 38sp to 357 mag and my Colt Police Positive I reamed out from 38 sp to 357 mag.

"Midway Load Map" says max 357 mag load is 13 gr. AA#9 158 gr. JHP.
"Lyman 47th" says 16 gr.
I did 17 gr. and the case stuck bad.

 

[rg1]

Just some more data to consider. Midway's LoadMap series 357 Magnum uses Win SP Mag primers, Win cases, 10" barreled universal receiver. They tested 23 different 158 grain bullets including the 158 Hornady Flat-Point and HP XTP. They give a warning that seating deeper greatly increases pressure. Note that Hornady's recommended overall length with the FP and HP 158 XTP is 1.590" oal. Midway tested the Flat-Point XTP at 1.580" and the 158 HP-XTP at 1.570". Midway says maximum average pressure should be 35,000 psi.
Midway's LoadMap says with the 158gr HP-XTP at 1.570" oal to start at:
9.7 grains of AA#9---26600 psi---1165 fps all in a 10" test barrel
10.0----------------28200-------1197
10.3----------------29700-------1228
10.6----------------31300-------1260
10.9----------------32900-----1292 and says use caution going above 10.9
11.0----------------33400--------1303
11.1----------------33900--------1313
11.2----------------34400--------1324
11.3----------------35000--------1335 and says this is MAXIMUM
Midway's LoadMaps were printed in the late 1990's and no longer in print. They published one in .357 Mag, 45ACP, 9MM, and 44 Mag and tested most available bullets at that time for the caliber.
Remember that they tested at .020" shorter than Hornady's recommended length. Midway's test with the 158 gr FP-XTP at a test length of 1.580" they list a charge of 11.7 grains of AA#9 as maximum showing 35000 psi.
I have heard said that Winchester's SP Mag primer is one of the hottest? Also, I believe Hornady's cases are sometimes heavier than some cases, so yes, it would be wise to check ALL start data and start in that area and work up. All I know is Accurate Arms data for AA#9 and Hornady 158 XTP's is ok in RP and Win brass with CCI 500 and 550 primers in my Colt Python and Marlin rifle. No pressure signs, no flat primers, and no sticky brass in the chambers of the Python. They fall out on their own. Start low and work up in your pistol!

 

[BBDartCA]

rg1 - great info, thanks!

 

[Clark]

My schpeal about the Midway Load map

How far down will the loads go?
357 mag max has gone below 38 Special:
"Speer 6" 1964 38 s&w special 160 gr. soft point 11 gr. 2400
"Speer 6" 1964 357 mag 160 gr. soft point 15 gr. 2400
Midway "Load map" 1999 357 mag Speer 160 gr. soft point 10.9 gr. 2400


What went wrong that Midway could get the max loads so far off and make
a useless load book?
They used an "Oehler System 83 and piezoelectric transducers, the latest
in industry standard equipment".

And I thought that the SAAMI registered pressure for 357 mag was driven by the threshold of sticky cases, and when thin walled 357 revolvers were made that were more springy, the SAAMI registered pressure for 357 mag was reduced so loads would not get sticky in the new smaller revolvers.

The pressure and the method for testing seems to have taken on a life of it's own.
Maybe it will evolve into a new life form on another planet, the pressure beast.