Reloading 75 Grain Gas Checks

G'Day jerryw
The 25-20 is a favorite for me for hunting small game for the pot. With its low end loads with a plain base bullet at 22 long rifle RF velocities it is eminently more effective than a 22 lr but at the same time not too destructive to the intended purpose of harvesting. It does not require equaling the 1300 fps of the standard high velocity loads of the 22 lr to be perfectly suited for the task. Anything from 800 to 1100 fps with an 80-85gn bullet will perform the task admirably.
I my experience with the 25-20 bullet weights in the 80 to 85gn range are the easiest to get good accuracy from. I speak specifically of cast bullets since that is what my experience has been gained with.
Not to say that heavier or lighter bullets wont shoot well just that perhaps the search for accuracy with these may be a bit more elusive than with bullet weights in the 80 - 85gn range.
The 75gn gc in our offerings is not one that I use much but certainly have used it. When I was the owner of a long gone 25-20 Marlin it was that rifles preferred design for a high velocity load. I never charted that load but do remember the velocity was in the 2300 fps range and used WC-820 powder. That load had exploded many a pestering chicken steeling raven from my shop in Alaska as well as proving adequate to dispatch a smallish 150pound black bear that offered itself as a target of opportunity. That little HV bullet took the top of that bears head clean off. BTW that smallish spring bear was some good eating!
Another powder I find very usable for this type high velocity loads is one the 680 powders that include WC-680, Win 680, and Accurate Arms 1680.
With the 25-20 Marlin currently in my possession its favorite high velocity load uses our 85gn FNGC dual crimp with a charge of 12gn WC-680 for right at 2100 fps. This load from this rifle holds very close to one MOA at 100 yards even with the very old Lyman All American 4X scope mounted on it.
A short list of powders I have charted some loads for with the 25-20 are,
WC-680
2400
Scott 4197
AA#5
Alliant 410
Trail Boss
Red Dot
One load that has stood out with my current 25-20 with the 75gn bullet you are asking about is,
case-RP
bullet-75gn Lyman 257420
primer-CCI-SR
powder-7.2gn 2400
Remember always start well below any suggested loads and work up reading the pressure signs your rifle is giving you with the components you are using.