Crusty -
Howdy !
How long is your rifle's barrel length ? If something like 20 - 22", you'd want to use a pretty fast burning powder.
FWIW:
I shot a .357 AutoMag-chambered rifle, set-up for true .358" calibre; to allow use of .35 calibre rifle bullets.
My rifle had a 22' custom stainless 5-groove 1-16 barrel. I got great accuracy results all the way out to 350yd ( longest distance I tried the gun ) shooting WW 296 under .358" 180gr bullets; and best groups shooting ( surprisingly ) surplus Remington .358" cal 150 PSPs ! That " .358 AutoMag " had case capacity just a tad less than what a notional " .35BR " would have. I formed my cases from 6BR and 7BR basic, and did use SR primers.
More recently, I am migrating my powder choices ( all rifle calibres ) over to powders w/ proven low sensitivity to temperature changes. I continued my .358" cal accuracy tests using a Marlin M-336 XLR .35 Rem.
A lot of people don't realize that the .35Rem has case capacity that puts ipotential powder choices square in the " benchrest" powder burn rate range. My XLR ( for whatever reason) made it out of the CT factory w/ a 1.5oz ( yes ounce ) trigger. I was OK w/ that , since I only intended to use the rifle for accuracy shooting onto paper targets.
My point:
While I obtained great results shooting the 150PSPs over a reduced charge of SR4759....... when I ran out of the 150s I switched over to shooting H4198 under Cutting Edge 150 Extended Range " Raptors ".
H4198 is the fastest burning rifle powder that ( to knowledge ) is proven to have low sensitivity to temp changes and has shown capable of providing superb accuracy in cases like .222 and .30BR. I have shot a one ragged hole 5-shot group @ 50yd, shooting the turned brass 150s over 20.4gr H4198. That is however...just 50yd; and I fer she want a valid 100yd load; so I'll be going up on charge wt when I continue my .35 Rem testing in my CVA Hunter.
Another thought:
When I first got into shooting " reduced loads " in .358" calibre, I had some concerns about the potential for experiencing " secondary explosive effects " ( S.E.E. ) . This is perhaps been shown to occur more in larger calibres ( .40" + ) when reduced charges of fast burning powder are being tried. I came across an article authored by a ballistics technician, that had performed S.E.E. testing to the point of even barrel destruction.
His data seemed to indicate H4198 was more friendly to reduced loads, than H4895. He also stated that no reduce load of any charge wt of 2400 produced any barrel failures. 2400 would be a potential fast burning powder choice for your application, however.... is not said to be temp insensitive. I have also not read that 4227 is temp insensitive. IMHO - for me, this all points towards H4198.
DK if any of that helps ?!
With regards,
357Mag