Why did this happen? 2 ammos, same zero.

[goodgorilla]

The answer maybe that the target was only 25 yards away, but here's how it went.

I zeroed the rifle with this ammo
Winchester M-22 Ammo 22 Long Rifle 40 Grain Black Plated Lead Round

then I changed ammo to subsonic
WINCHESTER SUBSONIC HOLLOW POINT (50 PACK)

After changing to the subsonic ammo, the zero was the same. I don't get it.

 

[SABuzzard]

Give it a little more distance and you'll really see the difference.

That Winchester ammo is pushing around 1,200 fps and your subs may be hitting 1,000 or little better. So the 200 fps difference may not be that apparent at 25 yards. You'd probably really see it if your supersonic ammo was of the "hyper velocity" 1,700 fps variety.

 

[Redmanss]

The difference in time of flight is miniscule, hardly any time for gravity to affect the projectile.

 

[JG26_Irish]

Shoot it at 50yds and the difference should be apparent unless the T22 ammo is not as fast and you thought it was. I can see a 1/2" vertical spread between Eley Black, at 1045fps and Lapua Center-X, which is about 1105 fps with the Lapua POI being higher and to the left. Spindrift causes the bullet to curve to the right in flight and the slightly longer time to tgt of the Eley makes it impact to the right of center if the Lapua is centered. If you watch close and do not blink you can sometimes see this if you have a good optic on the rifle and decent eyesight. It looks just like a pitcher's curve ball.

Irish

 

[ivanthesane]

Luck. At that close range though, it is like getting all 3 on a pick-3 lotto ticket (ie, 3 digit numbers) only 1000 possible combinations. Further out though, as said, will show the real difference