[mac1911M14]

Barrel length effects port pressure, not chamber pressure. Throat length can effect chamber pressure, but as stated above, your bullet will never touch the lands of an M14 barrel.

on a M14 maybe but what about current production barrels and in this case the SAI scout?

 

[mac1911M14]

I thought 4064 was used in the FGMM load. I would consider 43 grs of 4895 on the warm side.

you wont really know what powder is in the factory loads. They buy it in large bulk that gives them the what they are looking for in results burn rate and pressure

If you have any factory ammo that spreads out in a few lot#s break some down from each lot. Most likely you will find different powders and charge weights.

I emailed creedmoor to see what they used for powder in their 30-06 match loads and they stated each batch they buy is different and loads are worked up for each new lot. Our powder is not the same as commercial offerings.
Linked me to a review with some photos. Scroll down
http://bulletin.accurateshooter.com/2017/10/excellent-factory-ammo-offered-by-creedmoor-sports/

Im going to gander Federal uses what ever bulk powder that fits their needs at the time they order it. I have 1 round of federal 175 grain match. maybe I will break it down?