Decided to shoot my 700 BDL in 300 RUM. It was NIB. Picked up some 180 GMX's and looked on Hodgdon's site, I looked at their data for the 180 Sierra and did not give it a thought about the GMX being a Mono bullet. They list H4831 at 84-89 Grains. I never see the need to max things out so I loaded up some at 84 and some at 85 grains. The 84 grain loads shot the first five rounds out of this gun into right at an inch. I shot the 85's just for fun and it opened up to about 2". Today, I happened to look and see that Hodgdon lists the same powder for the 180 Grain TTSX at 77-82......
Sooo, am I over max with the GMX? I called Hornady and they were less than helpful telling me they do not list that bullet with H4831.
I did not see any pressure signs but honestly was not looking for them.
..........................My Sierra manual edition V lists a 78.6 gr starting load up to a 85.0 max load using H4831SC with their 180 grainers...................My Lyman 49th edition manual lists an 84.0 gr starting load and an 89.0 gr max load of H4831 using the 180 gr Swift Scirocco.
Interestingly, Lyman matches up with the same charges of 84-89 grains of H4831 using a 180 gr Swift just as Hodgdon does the same using the 180 gr Sierra as you point out.
Using the same powder but with different brand bullets of the same weight , the listed powder charge weights can vary and in other instances be the same as well.....
This is why when reloading, I always match the powders listed with the bullets listed. Otherwise, just as you are doing now, you are seeking reference comparisons to make sure you are ok and wondering if your above GMX loads were too hot by comparing them with TTSX listed data which show listed charges weights of 77 to 82 grains.
I think that you are ok using the 84 grain charge. But what I would do with the GMX and H4831 in your rifle, is to start all over again at about the 79 grain mark and work up from there.
