Should you head space off the belt or head space off the shoulder. Both are working fine but the full length just bumping the shoulder back about .002 might have a slight edge . both shoot fantastic. Some new remington brass I was fire forming shot one one hole which got me thinking about this . My old hornady book says off the belt, a lot of stuff I read says neck only . What do you long time .300 win. mag shooters think what works most consistantly over time?

The belt on this case is an artifact, a carry-over from the .458 which did not have a shoulder.

Pretend it is not there...

What I'm really meaning is that the belt was designed for a case that could not "head space" off a shoulder because it didn't have one.

BTW, the dimensions of the .458 (father to the 300 Win, 7mm Rem Mag, etc...) were borrowed from earlier H&H cases.

This is how cartridge development occurs - not much new under the sun!

Heck, even the "all new" 17 HRM is merely a necked down 22 Mag... the 17 HM2 is a neck-down 22 LR... ETC!!!!!!

WSSM's??? Guess what? Same head dim's as the afore-mentioned mags, just NO BELT....

I do not neck size any hunting ammunition as the close tolerances can result in more effort required to chamber a round.If a tiny bit of dirt or grit gets into the chamber or onto a case,it may be very difficult to chamber a round,not a good situation under hunting conditions.

quote:

Originally posted by wayles:
Should you head space off the belt or head space off the shoulder. Both are working fine but the full length just bumping the shoulder back about .002 might have a slight edge . both shoot fantastic.

A lot (most?) chambers cut for belted magnums are cut on the large side. Partly, this is to make up for generous tolerances in brass manufacturing - in particular for belted cases. That means, that you'll get quite a bit of stretch in the case when you fire it headspaced on the belt.

If you care about long brass life - at least in so far as this can be influenced by minimal sizing and minimal expansion - your best bet is to size for headspacing off the shoulder. The sizing you indicate, with the shoulder pushed back .001 - .002 is a great way to set your die. This is totally achievable with your FL die, and is often referred to as "partial full length sizing".

Exactly how much and what parts of your case the die will size in this setting, depends on the relationship between chamber and die dimensions. There are no hard and fast rules for this. All combinations of fat/thin/long/short in either die of chamber seem to be possible.

In general, you can also size .300 Win Mag cases with your NS die, but eventually, you'll have to FL size, when the brass does not retract sufficiently to chamber easily. One NS die which normally works well, is the Lee Collet die. Some people (myself included) shy away from regular NS dies, as they have trouble supporting the case during the sizing opertion, thus increasing the chance of runout. The Collet die or the Redding Competition Bushing dies are exceptions in this respect.

Like most things in reloading, nobody will be able to tell you "what will shoot best in your rifle", but if you care about case life, headspacing off the shoulder has the edge.

- mike

well brand new remington brass did it agin .Another 1 hole 4 shot group still using 76 gr of RL22 and 150 gr accubonds and fed 210 match primers. New brass to fired brass has a difference of about .017[smaller] makes me think there is somthing to the headspacing on the belt .Just Neck Sizing works in this gun also and so does just partial resizing of .001 to .002 sooner or later i will get it proved to myself just which one I want to stick with.Repeatable long range hunting accuracy is what I need .Thanks for your input thoughts I appreciate it plus any more you might have. I have been useing a rcbs and a hornady resizing dies both leave bright circles on the brass towards the base. My other .30 ,.26, and 6mm cal. dies do not appear to do this near as much appears to take a lot of pressure on the .300wm Wayles

quote:

Originally posted by wayles:
I have been useing a rcbs and a hornady resizing dies both leave bright circles on the brass towards the base. My other .30 ,.26, and 6mm cal. dies do not appear to do this near as much appears to take a lot of pressure on the .300wm Wayles

The bright ring towards the base of your sized cases simply indicates you get a fair amount of sizing in this area - the higher force needed to size the brass also points in this direction. As I stated above, exactly where and how much you'll get the case sized totally depends on the relationship between die and chamber dimensions. A large chamber with a comparatively narrow die will certainly do what you have described. It will work the brass a bit more than what is strictly necessary, but short of getting a different or even a custom die, there is not a whole lot you can do about it. In any event, safety wise, the head-shoulder dimension of the fired vs. the sized brass is the most important issue. So stay with your .001-.002 reduction, and you'll be fine.

- mike

I do a fair amount of target shooting with the .300 Win Mag and actually get better accuracy with F/L sized brass. I shoot a custom rifle built on a Wby Mk V action with a tight chamber. My reamer was designed with a small relief infront of the belt so even F/L sized brass will head space on the shoulder. Case life, however, is still dismal.

All I ever do for my .300WM is neck size and have brass that has been reloaded well over 12 times. If shooting in the same rifle you should have no problems.

quote:

Originally posted by Jacobite:
All I ever do for my .300WM is neck size and have brass that has been reloaded well over 12 times. If shooting in the same rifle you should have no problems.

Sorry for not being able to say the same.

I've a Ruger, and while NS was good in terms of accuracy, eventually the brass (after 4 or 5 reloads) became harder, that it was almost very difficult to extract after firing. This happened MANY TIMES.

Of course the cure was very simple. Used a Redding body die, and restored the shoulder and body to standard dimensions and everything then went ok!

Remember that in the field you need :

1) Pressure-safe loads
2) Mechanically perfect reloads (chambering and extraction)
3)Good accuracy

Gustavo

Right on target