Home Forums Reloading Big Game Rifles Resizing Belted Magnums

I am a newbie reloading for belted magnums. I've heard not to headspace off the belt, but to headspace off the shoulder. I should resize the belted cases just like my nonbelted cases.

So, I resized my belted cases just like the instructions in the dies recommend. Screw the sizing die 1/8-1/4 after it touches the shell holder. Does this mean I am resizing too much??? What happens if I follow the directions???

Does this lead to over working the brass? Effects accuracy?

How should I change my technique? Do I need to buy the Hornday Headspace Gauge to just bump the shoulders back 0.002" on my belted and NON-belted cases??

Thanks to those with more experience than me!!!!

Get the headspace gauge and bump back just enough to close the bolt smoothly. I've found quite a difference in the headspace gauge from new brass to once fired. No need to overwork that brass.

this

herschel34,

I have been loading belted magnums since the mid '70's. I size them the same way I size non-belted cases. I partially size one which generally causes something which makes the bolt hard to close. I turn the dies down about a 1/8 turn and try again until the bolt closes as though there were no case in the chamber. Then I back the die out maybe a 1/16 turn and try a different case. If it causes resistance I turn it back down and lock it.

This headspaces on the shoulder rather than the belt.

Herschel,
The reasoning here is this; if sized too much with the case head spacing on the belt, the case will stretch as it fires potentially causing the case to separate just ahead of the belt. Head spacing on the shoulder eliminates this and extends case life.

This again.

And again. Your initial post of bumping the shoulder .002" on both belted and non-belted cases was a good way to go about it. Use the headspace gauges to set up all your dies to set the shoulder back .002", there's no difference in loading a belted magnum and a regular case when you do it that way.

Thanks guys!!! This helps to clarify.

Is there any claims as to whether this may improve accuracy?

My gunsmith who is an experience and credible target competitor claims that you do get better accuracy in the 7rm and 300wm from full length sizing with a minimal size (using the technique described above) vs neck sizing. My one and only belted magnum has been a bit of a problem child so I don't have any evidence of my own to back that up yet.

Head space gauge kit = about the best $35 you'll spend on this hobby!

Agree with all above. Alternatively, I use an RCBS Precision Micrometer for measuring both case dimensions and in determining initial bullet seating depth.

What I have found when setting your case shoulder back .002 is not every case will be exactly set back .002. Each piece of brass apparently has slightly different elasticity for a variety of reasons. Some cases require more than one run through the resizing die too to get em there. After I resize all my cases, I chamber each one to make sure the bolt closes without too much trouble. In the past, it has been disconcerting to chamber a round only to feel it takes a lot of camming action to close the bolt. Chambering the empty cases helps prevent this. I also chamber all my rounds once they're loaded to make sure they function too...call me anal. ;-)

I do the same things.

Also make a feeler rod with a tiny hook on it and reach inside of every case to near the bottom and if you detect a thinning there throw that case out.

You can make one from a 7" long or so piece of coat hanger wire. Bend one end to a right angle and file a rounded edge on it.

[img]http://ts2.mm.bing.net/th?id=H.4526862260438641&pid=1.7&w=260&h=160&c=7&rs=1[/img]

It's also easy to unwind a large paper clip and bend a 90 on the end using small pliers.

Excellent question (well thought out): Sounds like you know more than you give yourself credit for. I'd suggest doing like ruffcut suggested and buy a case length gauge. LE Wilson makes a good one. You can also use your own chamber as a gauge. This method takes a little longer and you have to have a good feel for correct tension when closing the bolt down on the case. In the end it works just as well as a case length gauge since you are sizing your brass to fit your chamber. Once your sizing die is set up, you don't have to worry about it anymore and brass life and accuracy will be much better.

"What happens if I follow the directions???"

If you do it like that you'll likely make ammo that will chamber and fire.


"Does this lead to over working the brass?"

Who knows? It depends on the actual dimensions of your specific sizer and shell holder and your chamber and the amount of your press spring. The instructions you cite (1/8 turn) has a span of about 9 thousanths; that's 50% greater than the normal full headspace range of a bottle neck cartridge.


"How should I change my technique?"

It's a results type thing, size as needed for your cases to snugly fit your chamber. None of the various gauges are really "needed", we reloaded a long time before they became available, but they sure do make it easier to set the shoulders exactly where we want them...IF we actually use the gauge correctly. And cases do spring back differently because of brass alloy differences AND your variations in press operation. For a bolt rifle, there's no valid reason to set sized shoulders back 2 thou below the LONGEST FIRED CASE position; the fired case shoulders have already shrunk back at least a thou or more from chamber length.