300WM load development issues

[ta406]

ta406,
With only 75 rounds down the barrel its not even close to being broken it. It takes usually around 250 rounds before the rifle will settle down . Are you seating this bullet to magazine length or have you done some seating depth testing? If you have not and may want to give it a try I suggest you start at .015 off the lands and work back towards the cartridge case in .005 increments at the lowest powder charge listed for the bullet/powder/cartridge combination you are testing. Once the bullet seating depth accuracy node is found. Work the load back up slowly checking for pressure signs and accuracy until your highest velocity accuracy node is found. If you want to try all your load testing at magazine length you may want to work the load up in 1/2 grain increments until you get to 2 grains below maximum then drop to .2-.3 tenths grain increments until you get to 1 grain below maximum then drop to 1 tenth grain increments. You dont want to make big moves (1/2 grain) all the way up to maximum. You need to get finer as you go up so you don't miss something . Right now just looking at your velocities you should have an ES around 30 so your SD ( standard deviation , which is the more important than ES in my opinion because it is an indicator of vertical dispersion which is what you dont want) should be around 15 or so. That's not too bad but you should be able to get it to around ten , maybe less. You are close where you are at so you may want to test to either side of the load you have now (.2-.3 tenths grains). Any load testing should be done with the barrel fouled by shooting at a practice target until the bullet strikes stop their vertical movement and begin to cluster . Load testing can be tedious and frustrating at times so only make one change at a time and test it . And keep good notes in your reloading log book! A little patience here can pay big dividends. You can contact the BERGER BULLET techs at 714-441-7202 from 8am to 4:30pm EASTERN time MON thru FRI . We are always glad to help.
Thanks for using our bullets!
Take care,

I haven't done any seating testing yet. I have a Wyatts extended mag box so I can load to the lands. I did find that 77 and 77.5 grains of H1000 during barrel break in produced some decent groups with no signs of pressure at 2960 FPS. I think I'll reverse course and start there with your suggested seating test method. I don't have my notes handy but I believe both of those loads produced a SD of around 10 and ES of 20. And as a matter of fact, I was at .015 off the lands. The H1000 group size was half of the 570 groups. My whole reason for trying 570 was to ring out a few more FPS but with fall around the corner, I think I'll put that powder on the shelf and revisit it this winter.

Thanks to all for the great advice

 

[BEEMAN]

I haven't done any seating testing yet. I have a Wyatts extended mag box so I can load to the lands. I did find that 77 and 77.5 grains of H1000 during barrel break in produced some decent groups with no signs of pressure at 2960 FPS. I think I'll reverse course and start there with your suggested seating test method. I don't have my notes handy but I believe both of those loads produced a SD of around 10 and ES of 20. And as a matter of fact, I was at .015 off the lands. The H1000 group size was half of the 570 groups. My whole reason for trying 570 was to ring out a few more FPS but with fall around the corner, I think I'll put that powder on the shelf and revisit it this winter.

Thanks to all for the great advice

30 Thou off has worked very well in a number of different guns. A few 300 Win Mags and RUMS.

 

[excaliber]

I've yet to see a 300 Win Mag that doesn't like these two combos:
180 gr Nosler Accubond and 75 gr RL22
200 gr ELD-X and 79 Gr H1000

I'd check you action screws and scope mounting. You have something wrong and It's likely not the load.

 

[dfanonymous]

Groups were horrible. Probably close to 2 inches at 100 yards.

Did you crimp those loads?