I believe that the bullet diameter of a High Power should be .227"/.228" (I've seen both sizes published) and the factory cartridges featured something like a 70 gr. bullet - not sure without going to the books. But regardless it is a centerfire and it's legal to use for deer. Know this though...the 99 in a High Power is a highly collectable rifle to 99 collectors as is the ammo. Hunting with it could diminish its value. Have fun with it!
Here's a bit more info:
The 5.6x52R (.22 Savage High-Power)
By Chuck Hawks
This old North American cartridge was designed by Charles Newton and commercialized by Savage in 1912. The .22 High-Power is based on the old .25-35 Winchester case necked down to accept .227-.228 inch bullets. Reloaders should note the odd bullet size; the .22 High-Power does not use standard .224" (5.56mm) diameter bullets. It is unusual in being a .22 that was designed as a combination varmint and deer cartridge.
The High-Power had a run of popularity in North America starting back before World War I, but the cartridge got a reputation as a wounder of deer. Eventually American shooters went back to larger caliber cartridges for deer hunting, and the .22 High-Power fell into disuse and eventual obsolescence.
The .22 High-Power retains a modest level of popularity in Europe where its rimmed case makes it adaptable to the break action combination guns and drillings beloved in the Old World. In Europe the High-Power is called the 5.6x52R because it uses a 5.6mm bullet in a rimmed case 52mm in length.
No factory loads have been offered by the Big Three North American ammo companies for the .22 Savage High-Power during my lifetime. The Lyman technicians chronographed some old Remington .22 Savage High-Power ammunition, and in the Lyman Reloading Handbook, 45th Edition they reported an instrumental velocity of 2624 fps 15 feet from the muzzle of a 20 inch barrel.
The High-Power is currently factory loaded in Europe as the 5.6x52R. Norma 5.6x52R factory loads are imported into the US. The Norma factory load uses a 71 grain soft point bullet at a muzzle velocity (MV) of 2789 fps with muzzle energy (ME) of 1227 ft. lbs. Norma trajectory figures show the following: +2.1" at 100 yards, 0 at 200 yards, and -9.9" at 300 yards.
The 5.6x52R can be reloaded, and the Hornady Handbook, Third Edition has data for reloaders. Data for European shooters is available in European reloading manuals. IMR 3031 is recommended as a good powder for the .22 High-Power. Hornady makes a 70 grain Spire-Point .227" bullet (BC .288, SD .194) specifically for the 5.6x52R, which they describe as a "varmint and small game round." Hornady's test rifle for developing the following loads was bolt action Mauser 66 and they advise that for old lever action rifles their maximum loads should be reduced by at least 10%.
Hornady data shows that their 70 grain Spire Point can be driven to a MV of 3100 fps with 28.3 grains of N203 powder, 27.4 grains of IMR 3031 powder, or 27.6 grains of N201 powder. The trajectory of that load looks like this: +1.6" at 100 yards, 0 at 200 yards, and -7.5" at 300 yards. These loads used RWS cases and Federal 210 primers.