My 196 series mini would not cycle with a .040, ran just fine with the .045 . My 583 has a .050 and I'm happy with that , it throws brass about 12 to 15 feet but it fires every time I squeeze the trigger. I'm happy with total reliability . With a reduced gas port bushing and Wilson shock buffers installed the denting is almost non existent .

 

My 583 series has the buffer like what Misfire posted and a .05 bushing. Good bye denting the brass.

 

FWIW, I used an .050 bushing in a 582 for about 2.5 years including a several tactical and 3 gun matches. .045 would cycle 5.56 but not .223. The .050 worked perfectly the first year and I took it apart and cleaned everything. No problem. Worked perfectly the second year until I went to remove the gas block to deep clean it. The bushing had mushroomed slightly into the gas block hole. I could not get it out. I drilled out the hole to try and get an easy out or something in to get a better grip but no dice. Don't know what happened. Had to send it to ASI to remove. The only charge was to buy one of their bushing kits instead. Their bushings are slightly larger than the one they took out.
They recommended miking it once a year or more to see if the dimension starts to change on the end (mushrooming from peening). Running the factory bushing for a while now.

 

Until recently, ASI's bushings were all the same length which made them too long for the newer, thicker barreled 58X series Minis and a bit too short for the older 'pencil barrel' Minis so they could get mushroomed if clamped correctly in 58X series Minis. A correctly sized gas bushing can also appear stuck because of carbon buildup, however, a bit of brake cleaner soak followed by a few light raps with a hammer on the side of the gas bushing will loosen it up easily.

I have a 583 series Mini Ranch Rifle I've added a .045" gas bushing (correct length) and 2 Wilson 1911 buffers to, one around the gas pipe in the gas block to cushion the slide assy's forward stop, and one around the buffer guide rod where it inserts into the buffer bushing to soften the rear stop. This reduced my case dents and case mouth dings from significant to slight. A good result as I handload all my ammo and don't want dinged brass.

Note: Both the M1 Garand and M14 (M1A) share an action that the Mini is patterned after and both are famous for beating up your brass just like a stock Mini will do. Taming the recoil impulse to save the brass is a plus for your Mini as it's also been shown to aide accuracy.

 

I just installed a .045 bushing and a Wilson Shok buff on the rear and now my brass has no dents and the rifle cycles perfectly.

 

Another satisfied customer!!!

When you tune them to run great and shoot accurately, the Minis are a joy to shoot. Even though I have 3 ARs, my Ranch Rifle is the one I take to the range or to the woods for fun.