I'd think you'd need to stay at 70 grains or less for that twist rate. You may be able to make find a bullet that is slightly heavier work but unless you're willing to spend bucks on bullets that might work (like the 73 Berger HPBT) I believe you'd be better off holding the line at 70 grains or less and knowing reliably that they are going to work in your rifle.
Just sayin' ................
The Berger #1 says 1 in 9 or faster for the 73 and 1 in 8 or faster with the 75.
Find the length of the bullet and ensure your twist rate is indeed 1 in 9 that will be the key. Bergers VLD bullets are long in comparison to some so you may be able to shoot a heavier bullet if its short.
It seems the barrel itself is as much a factor in how heavy a 9" twist 22 cal will shoot well. My 5.56 ar (9" twist) will toss 5 75 grain priv partisan hpbt's in an inch at 100 all day long provided I do my part. I suspect it's a whether your rifle is a bit fast or slow of the 9" mark that's causing the differences. If in doubt, I'd stay lower than 70 grains.
morning, I have custom barreled 788 rem. I bought the rifle from a long range shooter from calif. the barrel is 29" long, #6 SS target barrel. I could not get the gun to target the 55gr. bullets. I have the barrel removed and rechambered to 223AI. I got some 72gr. VLD bergers. use 27.5gr. of TAC. fed 205 match primer, Winchester brass. ten shots .430. this is a smoking combination. I have an AR varmit. 24" #7 contour barrel, DPMS upper, Rock River lower. 6.5-20x44 Nikon monarch. Warne steel 1" rings. 23.5grs. Tac, Winchester brass, 205 match primer, nt black 55gr. bullets. shoots .250 outstanding accuracy. I have AR super match some load. target barrel same load bugholes. Rem. SPS left hand 223 outstanding accuracy. I have 4 223's. Cheap to reload. extremely good accuracy.gun)gun) T U
A 9 twist is a good compromise twist in .223. My 9 twist .223 has shot bullets down to 45 grains (the lightest I have used) very well. At the upper end, it stabilizes the 75 AMAX (the heaviest bullet I have used) and the Hornady 75 BTHP.
From reading some of the things Bryan Litz has written, however, I have learned that it is possible for a bullet to be stable enough to shoot good groups from a given rifle and twist combination, but the bc can still be degraded by insufficient twist.
The Berger bullets website includes a twist calculator, based on Bryan Litz's testing, that will help you to determine whether or not a given bullet can reach its full potential from a given twist. For example, when I input the data for the Hornady 75 BTHP, the Berger twist calculator indicated this bullet to be fully stable from my 9 twist barrel. By contrast, though the 75 AMAX is sufficiently stable to fly straight and shoot decent groups, it was shown to be insufficiently stable from a 9 twist to take full advantage of its bc. Moreover, its bc was degraded to the point where the AMAX offers no ballistic advantage over the BTHP in my rifle.