Recoil springs - testing

[Stu]

I'm thinking of trying out a 30 commercial I have but suspect the recoils spring is weak.

I base that comment on the fact that if you gently lower the toggle until the sear catches, the recoil spring doesn't have enough force to then close the toggle without manual assistance, (same for my byf). Doing the same with my Mitchell results in positive closure of the toggle. Is this a valid rule of thumb test ?

Could anyone suggest the right weight of Wolff spring for the 30 and 9mm, (shooting commercial ammo) ? I've read a number of posts on the topic but not really been able to reach a conclusion.

Thanks all.