must I full length size new brass?

[woods]

New cases are made to be loaded and shot without sizing being necessary. That being said, most could use some neck work. If they are bent or dinged they can be straightened. Sometimes the bullet grip or ID is tighter than you want.

But to talk about FL sizing is really a misconception. The new cases are smaller than your chamber in all dimensions (at least hopefully and theoretically). So running them into your die will not size the case body nor can the die be adjusted down far enough to push the shoulder back. So neck sizing is all you can accomplish anyway.

Personally I will neck size all new cases with a Lee Collet die with a mandrel that is the size I want, outside neck turn to the neck thickness I want, debur the inside of the flash hole, dry lube the inside of the necks and chamfer the neck mouth inside and out. Other than that I don't do any prep.

 

[Dean2506]

I always neck size new brass. I have found a lot of new brass has deformed necks i also trim all new brass to uniform lengths after neck sizing. I also chamfer and debur. Other than that i have really good accuracy out of new brass. I have however found the best accuracy in my rifles with once fired and neck size only. I only full length size brass that is fired in something other than bolt action or if the brass starts to get tight in the chamber. I also full length size if using in more than one rifle of same caliber as stated earlier. I have also gotten really good case life in the neck size only cases vs full length size. These are my processes and arent the only way to do it but they work well for me.

 

[Bart B]

I have also gotten really good case life in the neck size only cases vs full length size.

Some folks get 15 or more reloads per belted case with max loads by full length sizing them.

 

[Elkmen]

I just bought new Nosler, and Remington cases for my STW. For the nosler the prep was to chamfer the inside of the case mouth and load them. For the Remingtons I neck sized (numerous ones had digs aroud the mouth), reamed the flash hole, sorted by weight, champer the inside of the neck and loaded. I really like the Nosler case but its a lot of money and I am going to determine which case gives me the best accuracy in my rifle.

 

[Sully2]

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.

They can disagree all they wish...but it doesnt change FACTS! Once the round is fired it will force itself to conform to that ONE SINGLE CHAMBER ! All thats reqd after that is neck sizing for proper grip on the bullet ( and of course totla length) if attempted to fire it in ANOTHER CHAMBER...you may certainly run into prolems

 

[Sully2]

Some folks get 15 or more reloads per belted case with max loads by full length sizing them.

Its probably because they annealed the casings every 3rd or 4th firing

 

[Bart B]

Its probably because they annealed the casings every 3rd or 4th firing

I've got that many reloads on belted cases without annealing. And 47 on rimless bottleneck cases without annealing; muzzle velocity spread was about 30 fps with metered charges, not weighed ones.

 

[Bart B]

Once the round is fired it will force itself to conform to that ONE SINGLE CHAMBER ! All thats reqd after that is neck sizing for proper grip on the bullet ( and of course totla length) if attempted to fire it in ANOTHER CHAMBER...you may certainly run into prolems

That's almost right, but the outside dimensions of that fired case won't match the chamber; they shrink back. Neither chambers, case outside and case inside dimensions are all the same. As both are oval shaped a few tenthousandths (sometimes moreso) there's no such thing as a perfect fit.

Most folks don't know that the position in a chamber for both neck only sized and full length sized cases whose shoulders are set back a couple thousandths are virtually identical. The difference at the back end at the pressure ring doesn't matter because it's whats up front at the shoulder that counts. All bullets from each case type start out the same way.

 

[6mm Remington]

I don't resize new cases prior to using them. I trim the cases to the minimum length that the manual shows for that cartridge. That trues up the face of the case mouth, sometimes only taking brass off a portion of the case mouth. It also has the benefit of taking out any small dings or dents in the case mouth so bullets seat evenly and uniformly. After trimming I chamfer inside and out. I also like to debur the primer pockets on the inside of the case (only have to do that once for the life of the case) and use a uniformer on the primer pocket itself. Then I'm good to go.

 

[freak007]

They can disagree all they wish...but it doesnt change FACTS! Once the round is fired it will force itself to conform to that ONE SINGLE CHAMBER ! All thats reqd after that is neck sizing for proper grip on the bullet ( and of course totla length) if attempted to fire it in ANOTHER CHAMBER...you may certainly run into prolems

Would it be foolish to believe that all the chambers and dies were cut with the same reamer?

 

[Trickymissfit]

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!

I always do, but just felt it was the right thing to do from the start.
gary

 

[Sully2]

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.

Probably because their chambers dont even begin to approach SAAMI MINIMUM chamber size.....oversized to beat the band so anything smaller than a house cat can fit in and operate

 

[Bart B]

Probably because their chambers dont even begin to approach SAAMI MINIMUM chamber size.....oversized to beat the band so anything smaller than a house cat can fit in and operate

Why would you think their chambers would have to be so big?

The chambers were SAAMI minimum spec made with reamers ground to that spec. Sometimes, the throat would be a bit longer to accomodate heavier bullets. Sierra Bullets uses SAAMI minimum chambers in their test barrels, too, and feeds 'em full length sized cases holding bullets to test for accuracy.

 

[Trickymissfit]

for the brass case to form itself to the exact chamber deminsions the metal would have to go past the yeild point. Not gonna happen when the metal is moving about .005" total. Then when the primer is fired and the powder is burnt the chamber pressure from the burning gas will shock the metal almost instantly, but it never goes past the point of no return. Instead it goes as far as it can, and then springs back a little bit (mayber .0025"). If the metal didn't spring back you would never get the case out of the chamber with the extractor. Normally when you form an object by explosion, the master will always be a few thousandths bigger than what is wanted, depending on the alloy.
gary