Mini 30..
had mine for about 20 yrs. w/o shooting it much.
Trigger was so heavy/bad, it was about impossible to shoot a group.
Had my gunsmith (Doug Jones) do some trigger work & wow..what a difference.
Able to now shoot something that looked like a group.
Wish I'd met Doug a lot sooner.

Had a few issues with it, since I actually started using the rifle with some regularity.
Strange one, the trigger group would fall out of the rifle while shooting.
Reinstall trigger group, snap housing to lock it in place, & it'd fall out again, a few shots later
Back to Doug, who did a little filing on the stamped steel trigger hoop
(locks triggergroup in the rifle) & that seemed to take care of that issue.

Recently, had a problem with the charging handle/op rod sticking..my Mini 30 is SS, & kept very clean..
I had switched from using oil on sliding parts, to a teflon grease, then changed to a moly grease.
I'd changed the oem mainspring (due to age) & couldn't find a reason why bolt wouldn't close completely,
w/o giving the charging handle a little push forward, to close the bolt fully.
Then , sometimes, the bolt would stick in open position. Have to work it to get it free.
1st I cleaned chamber, bolt, op rod, frame areas where op rod travels,, top & rear of receiver, problem persisted.

Back to Doug to take a look..went over it examining everything, & eventually discovered that several of the
allen head screws holding the gas block to the barrel had loosened a bit . Not about to fall out, just needed to be tightened a bit.
All the cycling issues went away..I was embarrassed that I had not noticed this..

I never shoot steel cased ammo in any of my firearms..too many potential problems can be avoided by this & since I hand load,
my loads aren't much more expensive than steel cased ammo anyway. Been using A/A 1680 power exclusively for my 7.62 X 39 loads,
but recently bought & am experimenting with Shooter's World "300 Blackout" powder..
I've been using Shooters World powers in several applications & their data suggests they get higher velocities than other powders,
w/o exceeding safe pressure levels. Need to get my chrono working & see how accurate their claims are.