How does chopping a barrel alter velocity nodes?

[steffen707]

I know chopping the barrel will reduce muzzle velocity, but does that shift the nodes, require you to find completely new nodes, or does the same grains of powder yield another node, but just at that lower velocity?

My guess is that you need to re-establish a new node because of barrel harmonics changing.

One other question, lets say my 24" bbl 7mm rem mag shoots this 168gr ABLR really well with 62gr of 4000-MR. If i chop 6" off the barrel, the velocity will lower, but will the chamber pressure also decrease?

 

[tx_shooter]

From research with no measured scientific data - changing the barrel length will impact the barrel harmonics but the barrel is still long enough that the chamber pressure will not be changed in a noticeable way. The danger area will be getting max velocity with faster powders without blowing up the chamber. My primary rifle is a 20" 300 Win Mag. At the point I was using a small dead blow to open the bolt I reassessed my powder (and life) choices.

 

[steffen707]

so i should probably be looking at if 4000-MR is a faster burning powder and if I can slowly and safely go up in charge grain if at 62gr its only at 87% capacity. I care more about my life and accuracy than max velocity.

 

[Venatic]

Barrel length has zero impact on chamber pressure and no you can’t just look at the powder capacity and make a judgment that you can safely go up.
You may or may not be able get above 62 gr as every chamber /rifle is different to a small degree.
Chopping the barrel will definitely cause the POI to shift but not necessarily the node.