Max COAL vs SAAMI

[waitforit]

Help me think this through. Im loading 6.5CM, lapua brass, h4350, 147eldm.

I can load a ladder test to saami spec 2.800 inches and due to the AICS mags im using i can also load to 0.020 off the lands. In that case it will end up being 2.93 or so based on my measurements in my rifle.

For the same powder charge in the ladder - how much velocity difference should i expect in these scenarios? And how much additional top end velocity should i be able to get by loading long (and therefore using more powder).

Anyone ever try comparing these two approaches in the same rifle before?

 

[Harvey_NW]

In my experience the velocity usually doesn't change, sometimes if you're on the edge of a node it can. But it likely won't be much. Top end performance gain will just depend if you pressure out before you hit compression, or if your gun likes those loaded at .020" off.

 

[35WhelenAI]

I have typically loaded to the longest OAL the magazine will allow, obviously with the requisite distance off the lands. Work up your loads from that point. I know from experience it is splitting hairs with respect to difference in velocity one way or the other (seating short vs long) once you work the load up to the appropriate level using established methods.

I'm fairly new around here however not new to re-loading. I use to chase every extra foot per second and thought it was the greatest thing since sliced bread. Wrong. Find an accurate load with the bullet you like, sight it in, become familiar with the trajectory and there will be no issue with velocity.

 

[Tahoe1305]

Cartridge OAL — How It Affects Pressure, Velocity, and Accuracy « Daily Bulletin

Effects Of Cartridge Over All Length (COAL) And Cartridge Base To Ogive (CBTO) – Part 1 by Bryan Litz for Berger Bullets. Many shooters are not aware of the dramatic effects that bullet seating depth can have on the pressure and velocity generated by a rifle cartridge. Cartridge Overall Length...

bulletin.accurateshooter.com

Good read. I load long. Tend to get more performance. I feel I’m safe based on articles like the above and paying attention to pressure signs. For some guns like tikka with longer than normal throats this makes a big difference.