Thread: first time reloading.

The projectile may be touching the rifling.
Did the projectile have rifling scratches on it when you ejected the test round?
It may have pushed the projectile slightly further into the case as well so check the length with your measuring stick to check if it did shorten as this will confirm that the projectile is engaging the rifling.
You will need to seat the bullet slightly deeper if this is the cause of your issue.
Good luck.
Nice group.