LawrenceA wrote:I would suggest first you get a replacement.
Now is it really too stiff or do you damage your fingers?
Marlins can have sharp edges around the loading gate.
Once you have a spare you can either make the "spring" part narrower or thinner.
Narrower is easier but thinner is less likely to snap.
Whatever you do you need to keep the thinning consistent otherwise you risk causing a weak spot which will eventually cause failure.
Seriously take off half the material you think (not half the spring) you need to then try. It wont take much to take too much off.
Keep taking like half what you think you will need to until it works. Remember you do need enough resistance to ensure it pushes out of the way.
Also the retaining screw needs to be tight. If it unscrews the loading gate will not clear the loading gate and the action will jam.
I endorse everything you say.
But I would suggest the following be tried before any major surgery to the gate.
Lightly bevel the full inside edge, that has contact with the case rim, on the loading port in the receiver. Careful with this as you are only taking off the sharp edge that hangs up on the case rim and not noticeably rounding it.
Do the same with both the inside and outside leading edges of the loading gate again with the same caution.
You should find an improvement in ease of loading and fewer gouges on your brass.
Brass that has a sharp leading edge on the rim will still require greater effort.
Aside from the above there is a technique of using your index finger and thumb that seems to make the loading process feel easier and smoother. You might discover it by trying little variations in how you go about loading.