300 WinMag question

griffin ordway

New Member
Joined
Sep 25, 2018
Messages
4
Location
California
Hi All,
Not trying to stir up old threads....I've done massive research regarding reloading the 300 winmag, on this and other forums, and I can't find the answer to some specific questions. Just for some background: I am not new to reloading, but am fairly new to the belted mags; I am loading for use in a extreme long range target rifle (AX300); I will be using 195 grain Sierra TMK's; Using Norma brass.

1) Every reloading manual I have (quite a few!!!) shows the Max Case Length at 2.620, and the Trim To Length at 2.610...I have my trimmer set to 2.605 because there has not been one single virgin case that I've measured over 2.603! Once fired, they only expand out to about 2.608 max. Is this the norm for Norma brass, to be .007 short of Trim To right out of the box?

2) I totally get the whole "headspace" question with belted mags....that after the first fire forming, I am looking to headspace off the shoulder. My question has to do with bumping the shoulder back. My measurements show that after the first firing the case has stretched about .018, but then after the second firing it has stretched about another .003. So, do I bump the shoulder a couple thou after every firing, or just neck size until hard to chamber and then bump the shoulder. I've read a GazziliaMillion varying opinions on this....some even claiming one should FL size the case every firing (which I know is just wrong, but still believed by some).

Sorry for the "windiness" of my questions, but thought background and specific numbers would help.

Thanks all!!
 

cohunt

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Joined
Jan 21, 2016
Messages
2,391
Location
Colorado Springs, CO
Consistancy is accuracy
Perfect practice makes perfect
Reloading is frustrating but rewarding
Everyone has their own reasons

Personally, I fl size every time but bump my shoulder .0015" for bolt actions and .003 for semi auto.
As far as trim length, I let my brass grow past the minimum trim length then keep them at minimum...others like maximum length....

Your rifle will tell you what it likes
 

dok7mm

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Joined
Apr 13, 2015
Messages
1,770
Location
west texas
I don't bump the shoulder after first firing. As long as fired brass will chamber, I neck size.

On trimming, I measure chamber OAL or consult my reamer print. Also, measure your brass length AFTER FL resizing. I run .005" short of max length. That helps prevents excessive carbon build-up in chamber neck.
 

Deviant

Well-Known Member
Joined
Jul 12, 2018
Messages
528
Location
Nebraska
I would FL size but don't bump the shoulder until after second firing. I dumped my neck sizing dies years ago and haven't looked back. Just because you FL size does not mean you have to bump the shoulder every time.

Al
 

Trnelson

Well-Known Member
Joined
Feb 15, 2012
Messages
698
Location
Nebraska
I have had the best results, in my rifles, by neck sizing and only doing more than that if I had a hitch in chambering. Usually it’s after the third or fourth firing that I have a need to bump the shoulder back. If your rifle works better with a FL size, then run that!
As far as maximum case length, I keep my cases 0.005” of case length shorter than the actual maximum length my rig can chamber safely. Just cast the chamber and it will tell you everything you need to know. I rarely have an actual need to trim before the fourth firing. I anneal after every firing though. If your rifle delivers what you are looking for by trimming to 2.605” then run that length!
Reloading and long range shooting is a game of consistency. Record and control as much data as what you have to to get to the results you are trying to get the rifle to accomplish the results you are looking for. Some rigs are just more finicky than others and need more attention to produce adequate results.
Lastly, and most importantly, have fun and be safe.
 

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