What is actual difference in powder charge?

[BK7saum]

What is the actual difference in powder charge for a standard load and for a load where the base of the bullet is up in the neck?

Reason I ask, I have a 7mm short action ultra mag coming that is throated long to seat 180 bergers in the neck of the case. I have been checking load manuals and was wondering if this would raise the loads for max charges appreciably (and also velocities).

If anyone has a short mag chambering (SAUM or WSM) that is throated long, have you compared saami length chamber loads and velocities with long throated chamber loads and velocities.

You are essentially creating more combustion chamber which should allow for more powder/more velocity. Is this on the order of 10 fps, 40 fps or higher?

Just wondering. Load workup will tell the tale.

I plan on using H4831SC with 162 amaxs and H1000 or retumbo with 180 bergers and JLKs.

Thanks.

 

[madd0c]

Re: What is actual difference in powder charge?

Your statement that load workups will tell the tale is correct. You are also correct that seating the bullet out further will lower the pressures.
I don't use QuickLoad, but someone who does might be able to give you better answers to that question, however I sure would do as I always have done and start with a charge ladder and test from low on up with a chrony and looking at the cases to determine what load I would use.

madd0c

 

[BK7saum]

Re: What is actual difference in powder charge?

madd0c,

That's my plan to shoot a ladder over the chrono. Likely will try at 300 yards. When I shot a ladder test with my 6mm, it was amazing how the shots will string and then group at the node. Also allows me to determine max charge/pressure and find my accuracy node(s) at the same time.