A tight chamber is not going to get your pressure up before book minimum. If your factory loaded ammo went into your chamber it is not too tight. Now there is a chance if the neck is too tight. That can cause higher and eratic pressure. I highly doubt they made a tight neck chamber without specifically putting the spec on the barrel. My guess would be tight bores.
That and any roughness would cause pressure right away. The 2 rifles my customers have had didn't have a problem with pressure. One wouldn't shoot better than 1.5moa with anything we fed it. One of them threw a flyer 2 inches out of the group so often you could count on it.
Shep