Problems with compressed loads?

[jlvandersnick]

What are the potential problems with a slightly compressed load?

Details: 7mm RM, Norma brass fired 1x, FL resized with .002 shoulder bump, .0015 nk tension, 68.4 H 1000, Fed 215, 180 berger VLD, bullet seated .035 out from lands, about 2930 FPS, no pressure signs

Seating dept test showed .035 out to be the most accurate ...but the loaded cartridge seems to be slightly compressed.

A second question. The best load with the same gun, NEW brass, is 69.1 H 1000 with a seating depth of .010 into lands. Velocity here is about 2965 FPS Is it fairly common for loads with new brass versus fired brass to favor different seating depths?

Thanks
Jerry

 

[WildRose]

It all depends on the powder. Slow powders don't seem to mind at all.

Faster burning powders can reach overpressure very quickly when compressed.

Stick to known safe loads from reliable data sources and compressed or not you should do just fine.

With compressed loads though you really need to crimp the neck to ensure the bullets don't walk. If they walk from the pent up pressure then you won't get a consistent burn rate. Without a consistent burn rate you can't get good, consistent accuracy.

WR

 

[Buck Buster]

You did say slight,and you did say no signs of pressure. I say your in good shape. My most accurate loads are as you say slightly compressed, just at the end of the presses seating stroke I can hear a slight crunch. If you are not comfortable with the compressed load go to a faster burning powder, they will not take up as much room in your case but start out with loads below maximum and work up watching for signs of excessive pressures. Good hunting and be safe.

 

[sable tireur]

Here is some reference data from Hodgdon:

There are some pieces of information which you consider to be worthwhile yet provide no relative information with regard to a loaded cartridge. One of these is the distance from the lands. Yes, it denotes that the bullet is not jammed into lands but is off the lands. In order to see what the bullet's relationship is to the loaded round we need the OAL. Note that Hodgdon uses the SAAMI length 3.290" as a base reference.

 

[dok7mm]

Depending on your setup, two possible problems, that may or may not show up, are getting optimum seating depth established and getting your seater to attain consistent base to ogive length. If your rifle likes more jump, for example -- ultimate accuracy -- you end up with more compression or changing powders. Light compression should not be a problem.

 

[Wedgy]

You can try a drop tube or vibrating the shell with the powder in it so it settles better(on a orbital sander or anything that vibrates similar) and isn't pushing back on the bullets. I wouldn't crimp though.

 

[LongBomber]

For a compressed load i usually seat the bullet slightly then use a couple finders to rapidly tap the side of the case. Usually the powder settles enough to seat the bullet to the proper depth with no issues at all, at least for loads that are 102-105% in the loading manuals.