This bill passed in June 2014 and is in effect now.
Michigan House Bill 4283
During regular firearm deer season “limited firearm deer zone”
A .35 CALIBER OR LARGER PISTOL CAPABLE OF HOLDING NO MORE
THAN 9 SHELLS AT 1 TIME IN THE BARREL AND MAGAZINE COMBINED AND
LOADED WITH STRAIGHT-WALLED CARTRIDGES.
A MUZZLE-LOADING RIFLE OR BLACK-POWDER PISTOL LOADED WITH
BLACK-POWDER OR A COMMERCIALLY MANUFACTURED BLACK-POWDER
A .35 CALIBER OR LARGER RIFLE LOADED WITH STRAIGHT-WALLED
CARTRIDGES WITH A MINIMUM CASE LENGTH OF 1.16 INCHES AND A MAXIMUM
CASE LENGTH OF 1.80 INCHES.
Some suggested cartridges that have been advertised as legal.
Cartridge velocity grain bullet
.357 magnum rifle cartridge, 1500-1700fps, 158
44 magnum, 1500-1700fps,
460 S&W, 1400-1700fps, 240
Two AR15 uppers that are legal to use as applies to House Bill 4283
The .450 Bushmaster was developed by Hornady for the Bushmaster company and is based on the .284 Winchester case, case length measurements are 1.700” mouth to base and bullet diameter 0.452 inches. Bullet weighing 250 grains. Muzzle velocity is 2,200 fps (670 m/s) from a 20 inch (508 mm) barrel.
The .50 Beowulf cartridge is based on the .50 Action Express, case length is 1.650” mouth to base. The numbers for 300 grain .50 Beowulf are almost 1900 fps at the muzzle and 1400 fps at 100 yards, bringing a load of about 2300 and 1400 lb.-ft., respectively. In other words, the .50 hits hard.