185 JHP over WST horrific groups ? ? ?

First topic message reminder :

I am dialing in my Rock River Arms BE wadcutter (nice gun).  200g LSWC over 4.2 of WST is about all in the X at 25 yards using a bag to support my arm.  At 50 yards of course more open but that is as much lack of a ransom rest as anything, but all in the black.  Can't get the Federal Gold Medal Match that is guaranteed 1.5" with the gun so got some Magnus 185JHP as I keep reading about that.  I worked up some loads and at 4.6 grains WST and average 782fps with SD of 18 the groups at 50 yards (4 groups of 5 shots) were from 8-10" in size.  New starline brass, Winchester LP, all metered with an RCBS Chargemaster.  I was meticulous and they sucked.  I can live with the LSWC if the league starts up (doubtful) but not sure why the 185JHP is so bad.  I have Unique and Bullseye on hand too.  The 4.5 and 4.7 loads were a bit worse with that bullet.  Any insight? Thank you in advance.

Laminarman, I SEE THAT YOU ARE USING NEW STARLINE BRASS. GOOD, THAT SHOULD LEAVE YOUR SIZING DIE AVAILABLE. USE YOUR SIZING DIE TO APPLY THE CRIMP.  JUST HIT THE TOP OF THE BRASS ABOUT 1/16TH OF AN INCH. JUST STRAIGHTEN OUT THE FLAIR OF THE BRASS. THIS CREATES VERY EVEN BULLET PULL WITHOUT DISTORTING THE BULLETS DRIVING BAND. I JUST MIC-ED FEDERAL FACTORY MATCH AND ATLANTA ARMS . THEY BOTH MIC .471. JP


P.S. I HAVE NO IDEA HOW THIS MESSAGE GOT SO DARK. JP

Use the sizing die rather than the Redding taper crimp die? Is one better than the other? I still do re use brass and size for plate shooting

as JIMPGOV said factory stuff is at .471. I have some Old targetmaster and Win Super x 185 SWC stuff that also measures the same..