So I just got a new 300 wsm (Browning X-Bolt, love it!) and am working up an elk hunting round. I just spent some time at the range today with handloads and my velocity is nowhere near what the reloading manuals list. For example, the 180 grain x-bullet was supposed to generate 3036 at the max load of one powder. I got 2866. The 200 grain accubond was even worse--almost 200 fps lower on 3 different powders. Anybody offer any reasons why this is happening? Here are some observations on the day:

-Very windy
-Top loads did not necessarily develop top velocities. For example, one grain less than max gave best velocity from IMR 4350. This was true for 4 of 5 powder/bullet combinations I tried.
-None of the loads showed excessive pressure signs
-Weird clouds out. Very thin, high clouds. Maybe they affected my Chrony?
-FYI I would have expected not to hit top velocities as my barrel is 23" vs 26" test barrels. But 200 fps lower?

Any insight would be great, thanks!

You might want to try Alliant's RL-17 as it was made for the short mags. When working up my loads for the 300 WSM, RL-19 worked the best in my rifle with all the bullets I tried. I developed my loads before RL-17 was available, and will try it on my next powder run.

Welcome to the world of reloading. Rarely will you get the velocities listed in the manuals. Most often the data is from a pressure barrel not actually shooting and chronographing the load. The are also usually listing the barrel length as 24".

I use H-414 in my 300 WSM. Velocities (as you have seen) can vary greatly in different rifles and with different loads.

Were you having any pressure signs at max. loads?? Tom.