7mm mag low velocity

ForneyRider · March 5, 2009, 11:55 PM

I made some 162gr Interlocks with 68gr R25 which my load data gave ~3000fps.
This was a max load in one of my resources, but 70gr was a max in another source.

When I tested these loads, I was getting 2750fps average for 3 shots.

My barrel is 26in 1:9.5 twist barrel. The velocities of these loads are pretty far off what my other loads are.

I am wondering if the neck-sizing and bullet depth are affecting the pressure/velocity. I don't remember my OAL, but I tend to set it out to magazine length.

I have been pretty disciplined about working my loads up. I am thinking of incrementing in .5 gr to 70 and see how things go.

**Unclenick** · March 6, 2009, 01:33 AM

I ran that load in QuickLOAD and got a prediction of just over 3000 fps from a 26" barrel. I've seen a chronograph read off by 200 fps before. You might borrow a buddy's unit and see if it gives the same reading? Case capacity and COL do matter, too, but it's hard to get 250 fps worth of difference.

SL1 · March 6, 2009, 10:09 AM

IF the throat of his rifle barrel has eroded a lot, he might have lost 200 fps from the factory-new configuration.

How old is the gun and how long ago (in rounds fired) did you get chrono reasdings that were consistent with the same data source?

SL1

Horseman · March 6, 2009, 12:01 PM

For some reason 7mmRemMag loadings have been lowered more than other calibers in recent years. I've heard some shooters talking about 7mmRM loads from 30years ago and they are WAYYY over max according to modern manuals.

March 5, 2009, 11:55 PM	#1
ForneyRider Senior Member Join Date: December 4, 2007 Location: Forney, TX Posts: 725	7mm mag low velocity I made some 162gr Interlocks with 68gr R25 which my load data gave ~3000fps. This was a max load in one of my resources, but 70gr was a max in another source. When I tested these loads, I was getting 2750fps average for 3 shots. My barrel is 26in 1:9.5 twist barrel. The velocities of these loads are pretty far off what my other loads are. I am wondering if the neck-sizing and bullet depth are affecting the pressure/velocity. I don't remember my OAL, but I tend to set it out to magazine length. I have been pretty disciplined about working my loads up. I am thinking of incrementing in .5 gr to 70 and see how things go. __________________ When all is said and done, there is a lot more said than done.

March 6, 2009, 01:33 AM	#2
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	I ran that load in QuickLOAD and got a prediction of just over 3000 fps from a 26" barrel. I've seen a chronograph read off by 200 fps before. You might borrow a buddy's unit and see if it gives the same reading? Case capacity and COL do matter, too, but it's hard to get 250 fps worth of difference. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

March 6, 2009, 10:09 AM	#3
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	IF the throat of his rifle barrel has eroded a lot, he might have lost 200 fps from the factory-new configuration. How old is the gun and how long ago (in rounds fired) did you get chrono reasdings that were consistent with the same data source? SL1

March 6, 2009, 12:01 PM	#4
Horseman Senior Member Join Date: February 1, 2006 Location: Midwest Posts: 1,067	For some reason 7mmRemMag loadings have been lowered more than other calibers in recent years. I've heard some shooters talking about 7mmRM loads from 30years ago and they are WAYYY over max according to modern manuals.