Belted Magnums--Headspace on Shoulder or Belt?

MSLRHunter · #1 07-20-2010, 10:16 PM

Do most of you guys that load for belted mags prefer to headspace off of the belt or the shoulder? I load for 2 belted mags, 7mmRem and 300Win, and set the shoulders back 2-3 thou with good results and good brass life. In order for them to headspace off of the belt, the shoulders would have to be set back much farther than that right?

woods · #2 07-20-2010, 11:05 PM

It would depend upon what headspace you had at the belt.

IOW a belted magnum might have .005" headspace on a new case which is the dimension between the front of the belt and the recess in the chamber it will bear against. But that same case may have .020" between the new case shoulder and the chamber shoulder. Then after firing you would have to push the shoulder back .006" or more to have it headspace on the belt again.

But if your chamber has a headspace of .001" which, again, is the distance from the front of the belt to the recess in the chamber against which the belt will stop forward movement, then after firing you would only have to push the shoulder back .002" to have the belt again act as the headspacing agent.

Now all of this will vary with different makes of brass and chambers.

phorwath · #3 07-21-2010, 01:19 AM

Off the shoulder.

Buffalobob · #4 07-21-2010, 06:09 AM

If you have a custom chamber that is set to head space off the belt then use the belt. If your chamber and/or brass is sloppy then you should use the shoulder.

boomtube · #5 07-21-2010, 07:31 AM

Headspace for a reloader is NOT the same consideration as a gunsmith doing the chambering. WE want the cartridge to fit in that chamber with as little slop as possible.

That means we work with the shoulder for any bottle neck case, neither we or our ammo care where the belt is; you are doing good.

Rustystud · #6 07-21-2010, 03:53 PM

Belted magnums all headspace off the belt. The headspacing gauges don't extend to the shoulder area of the case. Headspacing off a case shoulder may leave you with a unsupported area in front of the case belt in the web area and thus allow a catistophic failure.

Nat Lambeth

BobbyL · #7 07-21-2010, 04:13 PM

Quote:

Originally Posted by Rustystud

Belted magnums all headspace off the belt. The headspacing gauges don't extend to the shoulder area of the case. Headspacing off a case shoulder may leave you with a unsupported area in front of the case belt in the web area and thus allow a catistophic failure.

Nat Lambeth

Agreed. Always head space off the belt. If there is something wrong then its in the brass/dies or the reamer. I have cut dies to allow for extra shoulder bump and that usually fixes the problems. If its long then you need to form the brass to that chamber and start all over.