Re: 270 win & H4350
I have burned quite a bit of powder in a 270 Win.. I have tried many different powders and yes I have used H4350 with 130 grains bullets even though I have not loaded the GMX's.
One of my best loads with H4350 is Hornaday's 130 grain Interbonds, shooting 54.0 grains of H4350 in WW cases and WLR primers I am able to get an average of 2968 ft/sec and my best accuracy with this bullet. I did go to 55.0 grains and I was able to get over 3000 ft/sec but I lost my accuracy.
From my experience if you want more velocity H4350 probably is not the best powder. You need something a little slower, such as H4831, RL-22, or in my case N165. My highest veloctity has been achieved with Magpro and with the 150 grain bullets IMR-7828 is a great choice.
For both accuracy and velocity it is almost impossible to beat H4831.