I tend to make "Tacticals" out of my older Mini-30's. Shortening the 18 1/2" barrel even one inch, two is better.
I had all three lengths. The factory, a "tactical" length 16 1/4", and an in between 17" one.
The one I cut to 16 1/4" my daughter now has. I still have the one I cut to 17" and the other is still at the factory length of 18 1/2".
Not much velocity difference. The short 16 1/4" one sometimes has a higher velocity than the longer ones, depending on the brand load fired.
The other things they have all had done are re cutting the crown, and hanging a flash hider on the muzzle.
It's not hard at all to improve on most factory crown's. I have simple hand tools from Brownell's, I think they ran about $55 with handle, a couple cutter heads and guide.
I can also use that handle and different caliber guides and cutters to bevel cylinders on revolvers, or bevel the end of the cylinder to facilitate reinserting the cylinder pin, for just a few other uses.
I've re-crowned 4 Mini's now, and my Remington 700 heavy barrel .308 also did noticeably better after cutting off a few inches and a re-crown.
1) Shortening the barrel in effect creates a stiffer barrel. Less hanging out there past the gas block to whip around.
2) The re-crown helps make the gases coming out of the muzzle "act the same"and not disturb the bullet in a different way each shot.
3) The flash hider on the end of the barrel is added weight to dampen the harmonics, in essence the "crazy vibrations" the barrel does right as the bullet leaves the muzzle.
Whatever you can do to tame that down will help accuracy.
The other two things that hurt the Mini's accuracy if not addressed are excess gas and the jolting of the op-rod.
Technically the op-rod movement is not an issue as it's still upon the moment of firing, until the bullet is long out of the barrel. But excessive slamming and velocity do not help things, all part of the taming down thing.
The Mini's are way overgassed. it's not uncommon for the Ranch rifles at least the older ones, to eject brass 45 feet away.
This ensures it will fire anything you shoot in it will work, even very low powered stuff. I don't know about you, but pretty much anything you find in 5.56 or 7.62 x 39 is full powered. Some 55 grain plinking ammo might only be 2800 fps. compared to XM193 being 3150, but it's not exactly slow.
The Fiocchi x39 I tested was pretty underpowered. While nice looking, accurate ammo, it only clocked 1950 fps., when everything else I've ever tried is 2350 to 2550. I'll avoid that.
You can reduce gas and metal to metal clanging in your Mini without compromising reliability in the least.
New Mini's come with an .080" gas bushing, whether Mini-14 or Mini-30. Ruger did that to simplify parts. It was an improvement for the Mini-30, as it used to have a .100" bushing. The .080" bushing used to come on the Mini-14, so no change there now.
But .080" is too much, most guys seem to like a .045" to .050". This will throw your brass around 10 to 15 feet. This is plenty enough gas to be reliable.
If you over do it and go too small, and your brass is "falling at your feet" that is too extreme.
Some guys brag about that, and to me, they are not far away from having a magazine fed single shot.
Another reason for the factory over gassing is the excess gas could help the Mini keep going even after becoming extremely dirty. I've found Mini's don't get that dirty. You can go for years without cleaning them, and many guys have done so, probably more out of laziness than trying to do "research".
Buffers also help by making the Mini feel smoother shooting, a lot less of the clang, bang, clang.
They also prevent stress of metal to metal slamming by cushioning both ends of the op-rod.
Wilson Combat 1911 "Shock-Buffs", the blue ones fit great on the Mini's. One goes all the way over the gas pipe in front, the rear one goes around the end of the guide rod for the recoil spring.
Some guys run just a rear one, but I feel the front one is the more important one.
When the op-rod comes back it will bottom on the receiver, but the recoil spring has slowed it down considerably.
When the op-rod goes forward there is nothing at all to slow it down, except for some friction of the op-rod inside the forend's heat shield, and the friction of the round being chambered.
That harsh slam into your gas block doesn't help, and the forward slam, opposite of what most scopes are built to withstand (recoil) are what gives the Mini the reputation of being hard on optics.
The eat up cheap scopes, better brands like Nikon and Leupold don't seem to have a problem. There are exceptions, I use a cheap Simmons 2-7x and a Centerpoint 2-7x for a long time on several Mini's and Marlin levers to test loads.
Some are concerned about using a buffer at all, that their thickness is going to prevent the bolt from going all the way back to eject a round, and also prevent the bolt from closing fully, and leak some gas from the gas pipe because the op-rod hole isn't all the way down around the gas pipe.
Bolt closing fully is a non issue. Close your bolt slowly, and the when the bolt assumes locked position, the op-rod will go about another 3/8" before stopping.
Preventing the bolt from coming all the way back, is a good thing. it isn't much, and helps dampen harsh ejection, like using a smaller gas bushing but to a lesser extent.
Brass is easier to find and less dinged up if you reload.
The gas pipe is an inch long, 1/16th is not going to let much extra gas by. That's the thickness I use, made by slicing a Wilson buffer in half.
Stock Wilson buffers are more like an 1/8".
I'm hedging for reliability by using a thinner buffer, I still get some cushioning effect, and I have twice as many buffers for the effort.
Tacticals with 16 1/4' barrels, or any other Mini that has had the barrel shortened to that length, will need to run a bigger gas bushing. Like stay with the .080" one in a Mini-14.
The Mini-30 I shortened for my daughter wouldn't even function with the .065" bushing that works just right in the other two Mini's. I had to put the stock .100" one back in.
Some guys with newer Mini's are reporting that their ejection is sane, like in the 15 foot range. If that's the case, I wouldn't need to do anything to the bushing.
It's fine the way it is.
If your Mini is shredding the front buffer, you might need to do smooth any sharp edges on the front of the op-rod with Emery cloth.
Some of the op-rod face lips are almost sharp.