Yes, too much freebore can affect both velocity and accuracy. Freebore affects the bullet in basically the same way as throat erosion - it gives the bullet a chance to skew before hitting the rifling and also a place for gas to escape around the bullet, which would affect accuracy and lead to throat erosion.
Still, if you are comparing your results to published data, your result may be normal. AFAIK, published data, unless otherwise specified, is taken with a 26inch barrel. Since velocity drop is about 50-70 fps per inch, your results are not too far out.