Depends. If you mean the Ruger Mini-14 or Ranch Rifle, yes, you can. It is chambered for .223 and 5.56x45 ammo. If you read the owner's manual (available on the Ruger website) it will tell you that on page 13. The Target Model is ONLY for .223. Of course, the 6.8mm and the Mini-30 use different ammo entirely.
The Ruger Mini-14 Ranch Rifle marked as .223 can safely fire the .223 AND the 5.56 NATO military cartridge. The Ruger Mini-14 TARGET model should only fire .223 ammo- no 5.56 mm
9mm Luger.
I have had good success with Federal rifle ammo.
"Best" is subjective. A really good definitition of best is, the ammo that functions the most reliably in your particular gun.
If the rifle has stampings of .223 Rem or 5.56x45mm on it, then yes it can. If it has stampings of other cartridges, then don't do it! Almost all guns have markings of their caliber on the reciever or the barrel. If your confused, find a professional (Gunsmith, firearms enthusiast,etc) and ask. Hope this helps.
It is the same cartridge
Try different brands to see what works best in YOUR rifle. Federal makes very good ammo that shoots well for many people.
11.5 mm bullet diameter
556 mm with stock retracted, 730 mm with stock extended.
20 mm cannons.
.0219 inches OR .556 mm (USG)
Probably 25 gauge, which is .556 mm thick. However, 26 gauge is close too, it is .478 mm thick.