6 arc extended COAL

[270quest]

So with the JO bottom Metal, it appears it opens up COAL to at lease 2.4", maybe 2.450...In turn this will allow seating of Longer bullets not so deep into the case, impeeding powder capacity and compressing it.

So, as a general rule, with bullets seeding out longer, is it safe to assume that would lower pressures and possibly allow one to take a load up a bit more?

As an example, Hornady bolt data list a max load of H4895 of 27.1 with a 108, loaded to 2.260" OAL. If a bullet can now be loaded to 2.450", that additional room in case may allow for a touch more powder before hitting that max pressure? Hypothetically?

 

[wind gypsy]

At what COAL is Jam with that bullet? At some point being close to the lands increases pressure.

In theory there is a middle ground where pressure is lowest off the lands a ways but not stuffed too deep in the case. The actual graphed example I've seen in this was in 30-06 with shorter 150 gr round nose bullet so it might not extrapolate perfectly to a stubby case with a longer bullet..

 

[KyleR1985]

you are barking up the right tree.

The only thing you’re up against is that the 6ARC chambers I’ve had hands on all jam before optimal bullet seating depth, or maximization of magazine space.

Maybe your gun is different.

I haven’t measured a 6ARC that didnt jam prior to taking advantage of loading long.

I think if you want to get to where you’re going, you’re throating the chamber, or going to a 478 case head to do it.

 

[KyleR1985]

All of my 6ARC measurements have jammed at 2.35” or less with 95tmk 108eldm 87vmax 90eldx

 

[Ganderzone]

Anyone ever have a 6mm arc throat extended? I have a kelblys short action that gives me all the room I could want, no magazine limits. I'd be curious to see how far you could move the bullet out to the shoulder for more powder capacity.

 

[KyleR1985]

108 @2.42” would be ideal.

95 @2.35” would be ideal.

I’ve jammed the 95’s around 2.3-2.33 if I remember correctly on my barrels.

 

[Ganderzone]

That right there is what I needed, you the man! I have a ppc bolt face on my SA so it's between the arc or the Grendel.