I shoot the 210 exclusivly with the 300wby. Hunting and 1K comp......My comp loads have been as low as 74 gr RL25 to as high as 82 gr. I have shot from 72 gr all the way up to 85 Gr RL25 in my comp guns...never did get to the "max max", but I was close. My Hunting 300 (rem action, 30" Spencer1-10 twist) was 83 with moly, but it was just to hard on brass....down to 81 gr with good brass life. Remember..this is with Moly in the hunting gun...I had to reduce 5 grains to get the same velocity with naked bullets!!! And no, I can not explain the massive charge difference between moly and non moly...I just know that I almost blew my face off trying to shoot 80 gr of RL 25 with naked bullets!!! I put a big red skull and cross bones in my journal just to remind me!!
None of my 300's have the wby free bore......although I am mag limited with my hunting gun by about .12". Luckaly it shoots just as good with the bullet jump. My comp guns are loaded so I can load out to 3.95" and just touch the lands.......very, very long OAL.
Now, what kind of PSI signs are you showing? I usually work up every gun to the top....just so I know where the "end" is. Also, there is a danger to life and limb with to light of loads.....secondary explosion.....very, very bad!!
Also, try and barrow another chrono......set them up so you are shooting through them both together. That will tell you about your chrono.
Good luck...the 300 WBY/ 210 VLD is an AWSOME lr combo!!!