Hey there folks,
I am reloading .357 magnum cases. I have some IMR SR4756 powder. My Hornady Handbook doesn't have this specific powder data available. I checked online (the IMR website) and it redirects me to the hodgdon site. I am using a 125 grain HP/XTP. According to the Hodgdon site, I shouldn't use load any more than 7.8 grains. I checked several other online resources with different results. The problem is that there is a lot of space between the powder and bullet. I know that this isn't good. I am going to pick up another book soon but in the mean time, does anyone have a suggested load that will work? I am shooting a 4" 686. I am new to all this and was hoping that someone could point me in the right direction.
Thanks

Not as much a problem as you seem to think.
Medium powders in .357 cases do leave quite a bit of room, but they shoot fine as long as you don't double charge.
Other choices are available.

125 GR. HDY XTP Hodgdon H4227 .357" 1.590" 18.0 1692 34,400 CUP 20.0 1839 42,000 CUP
125 GR. HDY XTP Winchester 296 .357" 1.590" 21.0 1881 38,400 CUP 22.0 1966 41,400 CUP
125 GR. HDY XTP Hodgdon H110 .357" 1.590" 21.0 1881 38,400 CUP 22.0 1966 41,400 CUP
125 GR. HDY XTP Hodgdon Longshot .357" 1.590" 8.7 1529 33,000 CUP 9.7 1647 42,000 CUP
125 GR. HDY XTP IMR SR 4756 .357" 1.590" 6.0 1169 18,600 PSI 7.8 1427 30,600 PSI
125 GR. HDY XTP Hodgdon HS-6 .357" 1.590" 9.8 1493 34,400 CUP 10.9 1629 42,100 CUP

I haven't tried recently, but I believe that a double charge of SR 4756 will overflow the case. I use SR 4756 quite a bit for medium .357 Magnum loads. It is also one of my favorites for 9mm, because even a compressed charge is well within the margin of safety.

So how much powder should I be loading for a 125 grain?

Hodgdon has an excellent reloading center that covers Hodgdon, IMR and Winchester powders

http://data.hodgdon.com/main_menu.asp

Always go by the load data, never use the fullness of the case as a guide. For example, when you charge a 45 colt case with a target load of fast powder, you practically hear an echo when you drop it. In that scenario check each charged case well with a strong light before seating bullets to look for double charges.

Thanks very much for the info. I am going to pick up a new reloading book also. I am just get a bit nervous when you can hear the powder moving around in the case after the bullet is seated.
Any suggestions for reloading manuals?

Lyman 49th and Sierra are my favorites.

I just documented 125,000 loaded on my Hornady LnL. I have been loading .357/38 Special and .45 Colt recently.

I don't have any loads that fill the case to the bullet except some 777 fffg Colt loads, and they are pretty hot.

I try to stay in the middle of the published data to start, and then go down, rarely up. I want to shoot 3-500 at the range, not 20 and go home hurt.