[Ammunition Attrition]

Per Loadbooks:.357Sig
in Sig P226 with match-fit 6" Bar-Sto (Mike Bay Gunsmith)
9.0g IMR label 800X (hand-measured of course #!!! 800X)
147g XTP
1.15" COAL (fits 226 mag and Bar-Sto chamber no prob )
Fed GM 100 primer

V=1463 fps avg. five-shot string :tequila:
Acc= yet to be established. All five on 6" white of 8" target at 25 yards.

That kind of V potential is the only reason I mess with 800X.
More practical at 8-8.5g and around 1300-1400 fps with 147g.
Or less.

 

[Ammunition Attrition]

Need a penetrating piggy round that won't fragment and explode shortly after impact, so...
147g Mid Atlantic Hard Cast Flat Nose (BH 17)
http://store.midatlanticbullets.com/38caliber105grainflatpoint-100countmatchgrade-1-1-1-6-2.aspx
They gas checked real smoothly in a Lee .357/.38 Sizer die, which I did to hopefully reduce leading and will start testing them soon to around 1300-1350fps using WSF and 800X (see above post for 147g potential Velocity of 1400+) with accuracy critical.
COAL: 1.168" (long for case capacity and fits Bar-Sto custom match 6" bbl fine, also P226 magazine with no issue).

 

[Ammunition Attrition]

Be careful there are not may loadings for the 147 grain in 357 Sig, however 800X and LongShot may yield your best numbers...
I did a Pull-Down of Underwood's 125 FMJ load, and the way I obtained these was a forum member here, had his gun blown up. The cartridges may have been damaged and possibly not fully locked in battery or a bullet setback issue. Although Kevin was pushing them pretty hard with these loads.
The load data is in the GlockTalk 357Sig section click the link below and then to go to post #58
http://www.glocktalk.com/threads/357-sig-data.220520/page-3

http://www.midwayusa.com/product/955169/loadbooks-usa-357-sig-reloading-manual?cm_vc=ProductFinding
You're probably familiar with these. The old Hodgdon/IMR/Winchester powder load pages in here, along with the old Speer (heavy) are good baselines to start. The variations in max loadings aren't as insane as for our 10mm, of course.