must I full length size new brass?

[sdoc]

well as long as they fit in the gun nicely sizing them the first time wont do much for me will it? and its a stock savage hunting rifle soon to lose the origional trigger and stock. reason im being cheap is ill proubly rebarrel to 257 stw in the near future and the dies will likely be useless to me but i can always sell em

[Hunter Welch]

Originally Posted by sdoc

well as long as they fit in the gun nicely sizing them the first time wont do much for me will it? and its a stock savage hunting rifle soon to lose the origional trigger and stock. reason im being cheap is ill proubly rebarrel to 257 stw in the near future and the dies will likely be useless to me but i can always sell em

It might make a slight difference in accuracy I would assume, but it just depends what you want out of this load of rounds. I would just wait until you shot them once and then neck size them. I didn't case prep my new Winchester brass for my new SPS Tactical and it shot MOA or better groups. So the choice is yours really.

[Loner]

I frequently get my best groupings from new unsized brass. If I see a bent neck I'll
neck size it, other than that I don't touch it other than the flash hole. You have it backwards, buy the full length die, Back it off a turn and it will work fine as a neck sizer.

[Gene]

After several firings, you will need a F/L die anyhow, might as well get it now. As long as virgin brass fits your rifle chamber OK, you need do nothing. Many factory cases have bent necks, and you neck sizer buttom should remove these. I suggest you champfer the mouths inside and out for the first two sizings. Don't forget to check case length and trim if necessary each time.

[Bart B]

I've shot 15-round test groups with 30 caliber belted mag's at 1000 yards with brand new and properly done full length sized brass that equal or best current benchrest records. No brass prep was done to primer pockets, flash holes or neck walls but the new case necks were chamfered then resized with a standard full length die for uniform bullet tension.

The most accurate belted case rifles I know of all performed that well with either new or full length sized brass using the right type of dies. I'm referring to the size of the largest group fired in tests, not the smallest. The largest group fired is what one can count on all the time. The smallest groups only happen about 5% of the time and are the worst ones to judge accuracy with.

Backing off a standard full length sizing die to neck size is a popular technique But it usually forces the fired case shoulder forward causing a tight fit of the case in the chamber. And that makes the bolt close in different places for each shot; especially if the bolt face ain't squared up with the chamber axis. Sierra Bullets tried this fired case sizing method (as well as neck only sizing) in the early 1950's when developing reloading techniques for their cases used to test their products for accuracy; it didn't work. They got best accuracy properly full length sizing their cases. Sierra still does using Redding full bushing dies for cartridges the bushing dies are made for and conventional full length sizing dies for cartridges that don't. However, if one sets a fired case shoulder back too far with a standard full length sizing die, backing the die out a full turn may produce better results; expecially with rimless cases.

[Sully2]

Originally Posted by sdoc

i just bought a 7mm stw and 2 bags of new brass do i need to full length size the new brass? or can i just neck size it? reason i ask is because it would save me some money not buying a full length die, as i already bought a competition bullet seating die and would just buy a neck sizer. thanks!

IF you have 1 RIFLE of that caliber ONLY then you can do what Hunter Welch said. BUT it might work ONLY in that one rifle. If you have 2 in that caliber...then you MUST go the whole route

[Bart B]

Originally Posted by Sully2

IF you have 1 RIFLE of that caliber ONLY then you can do what Hunter Welch said. BUT it might work ONLY in that one rifle. If you have 2 in that caliber...then you MUST go the whole route

US military rifle teams shooting 30 caliber magnums in 1000 yard matches will disagree with this. The shot their best scores using new .300 Win. Mag. cases or .338 Win. Mag. ones necked down to .30-.338. And one several-hundred round batch of ammo did very well indeed across a dozen or more rifles. Civilians did the same thing.

My best 15 to 30 shot test groups with my .30-.338's at a thousand were smallest with either new cases or fired ones full length sized properly. They're equal or smaller than current benchrest records. I and others never got best accuracy with neck sizing previously fired cases.

So you don't need to go the whole route. Unless you really can't full length size your fired belted cases correctly.