Hodgdon recommends their H4895 for reduced loads. Apparently it is especially
forgiving, burning well at lower pressures. If you check their site, I believe they have
some specific recommendations on lowering charges with it for youngster hunting
loads.
However... a full power normal load in a 7x57 with a 139 gr Hornady Interlock (ordinary
flat based JSP) will not kick much. If it is more than he wants, dial it down a touch.
I used this inexpensive bullet for my practice loads when getting ready for Africa and learning
to shoot over shooting sticks, standing - a new skill for me. IIRC I used about 33 or so gr of H4895
and this was very low recoil and shot about an inch at 100 yds, all I could possibly need for
practice shooting. I did need to adjust my scope from full power loads a little bit, but if this
were his hunting load, that problem is gone.
I practiced hitting 6" dessert sized paper plates, a handy practice target for deer hunting,
too. Cheap, and a good goal is to keep the shot on the plate. Good goal for your grandson.
OK here it is directly from Hodgdon:
Hodgdon Powder Company has found that H4895 can be loaded to reduced levels. H4895
was chosen because it is the slowest burning propellant that ignites uniformly in reduced
charges. To create reduced loads, the 60% formula is recommended.
Find the H4895 load in the Reloading Data Center for your caliber and bullet.
Take the maximum H4895 charge listed and multiply by 60% (.6). The load may
be adjusted up from there to achieve the desired velocity and accuracy.
This works only where H4895 is listed. DO NOT use in a cartridge where H4895
is not shown.
Example: 30-06 cartridge with 125 gr. Sierra SP bullet. Max load shown in the Reloading
Data Center with H4895 is 53.7 grains. 53.7 X .6 = 32.2 grains. The shooter begins
with this load, and may work up from there to obtain the desired velocity and
accuracy for his reduced load.
Call Hodgdon Powder Company if additional information is needed, 913-362-9455.
So, for 7x57 and 140 gr, the max shown on Hodgdon's online data is 37.5 gr.
Multiply by 0.6 and you get 22.5 gr. You can work up from that to get the
velocity, recoil and accuracy combo you want. That should be REALLY mild
at the start. But it is nice to know that the powder will "behave itself" at those
low charges, officially from the experts.
Bill