Just finished my load development in the new 29" Bartlien barrel with 1/8 twist. Here are some loads that work well.
US869 87.5 gr. 195 Berger 3,143, Hornady brass with CCI 250 primer. c.o,a.l was
3.868".
H870 87.5grs. 180 VLD, same primer and brass, Mv was 3,250, c.o.a.l. 3.800
RL33 85.0 grs. same primer Norma brass 180 VLD,
,3187, C.o.a.l. 3.840.
I am going up with the 180 and 195 and with Hornady 300 H&H brass which is much stronger. I have tried Magnun and RL26, IMR7977 with good results.
Careful pushing the VLDS over 3200pfs. My gun smith said the start to get lead sag or bulge and start really srubbing off the copper causeing excessive copper foul. I found my best load is 80.5gr of retumbo, cci 250's amd nosler brass with the 180 vld hunters at 3.707 c.o.a.l.
I dont like the hornady brass cause they are not as consistent in weight as the nosler are.