Sizing new brass

[SRP Shooter 1]

Do you size and trim new rifle brass before loading? I recently had a batch of new.270 brass I was about to load and found a lot of the case mouths were out of round so I ran them thru the sizer and checked the length and found a lot of them above trim length and some over max. Just curious.

KS

 

[Martin52]

I run an expander mandrel through the necks on new brass as it can be pretty tight and also variable, I don't usually resize but I do check length and trim as necessary, then chamfer inside and outside.

 

[Ramjet]

I always run my new brass through a Lee Collet Neck Sizer to clean up the dented necks

 

[K22]

Yes, I FL size virgin cases but with no shoulder bump or extrusion (i.e., lengthening). To accomplish this, the FL die is set so the die touches the shoulder but does not bump it back or extrude the case. The only way I know to do this precisely is to use a caliper and bump gauge to measure the before sized case and after sized case head space to set the FL die.

The reason I do this is most of the medium quality brass I buy (i.e., Rem, Win, Federal, Hornady) often needs to be uniformed due to manufacturing variations which included irregular neck and necks out of alignment with the body of the case.

If after sizing, the case length is greater than the virgin case length, then you either extruded the case by sizing it without the die touching the shoulder or the expander button is oversized and pulled the neck longer. Most likely, you extruded the case.

As you fire virgin cases, they will fire form to the rifle chamber if you don't bump the shoulder back. This is desirable. Once fully fire formed, eventually you will have to bump the shoulder back a very slight amount, usually about .001 to .002" so the case will chamber.

 

[Charlie-NY]

I'll run cases through a FL die just to round out the necks. I don't trim or uniform case length until after cases are fired. IMO, there's a good chance that case length will shrink as the initial firing expands cases to the chamber and could pull neck brass down. It also makes sense (to me) to trim cases that have been properly resized to your chamber, rather than before resizing.

 

[Straightshooter1]

I always run my new brass through a Lee Collet Neck Sizer to clean up the dented necks

For virgin brass, I do the same.

I've tried just a sizing mandrel the same size as the collet die has to round out the neck, but seating remained uneven and too firm. The collet die made for easier and more uniform seating. Apparently, the squishing action of the collet die smooths everything out inside the neck.

 

[Bill Norris]

From taking even a quick peep at the case mouths of new brass even Lapua I would never attempt to load it without first running an expander into the necks to even out all the dents and bruises. I see no need to try and re-size the body of the case because at this point the case is as small as it's ever going to be.

 

[BigBolt]

I double check all my 30/30 as I have found they do need additional work. On my new brass .500 S&W amd 45/70 brass I just trim to my specs and do not resize. I use to trim my 40S&W cases but found after some testing they really did not need it. However, I do run them through the sizing die.

 

[White Eagle]

Always resize new brass just for the reason you mentioned
there are better brass manufactures so sometimes it's not as critical as with some others

 

[D-4297]

Since I only use Lapua SRP for .308 , TR , I do a light deburr on the inside of the neck , to lessen the stress on the expander . Then run the expander , periodically check I.D. , and then prime and load If the case hasn't come up to full size , I don't bump till it does . Then ; only .001 .

 

[JFrank]

From taking even a quick peep at the case mouths of new brass even Lapua I would never attempt to load it without first running an expander into the necks to even out all the dents and bruises. I see no need to try and re-size the body of the case because at this point the case is as small as it's ever going to be.

I’m with you

 

[Coyotefurharvester]

I haven't found long new brass, mandrel the necks and load.

 

[big5ifty]

Do you size and trim new rifle brass before loading? I recently had a batch of new.270 brass I was about to load and found a lot of the case mouths were out of round so I ran them thru the sizer and checked the length and found a lot of them above trim length and some over max. Just curious.

KS

I do not.

Normally, new brass is good to go, depending on the application.

It is not normal for new brass to be over length.

 

[Alguapo]

yup

 

[Webster]

Do you size and trim new rifle brass before loading? I recently had a batch of new.270 brass I was about to load and found a lot of the case mouths were out of round so I ran them thru the sizer and checked the length and found a lot of them above trim length and some over max. Just curious.

KS

Don't know why guys are obsessed with trim length. If you look at a chamber blue print there is about 0.040” space in front of a cartridge neck. The chambers are cut long for the neck so any factory loaded ammo will chamber. There should be no interference unless you have a hard carbon ring. I don’t worry about it for my varmint rifles unless it’s at least 5 thou over. I don’t think I could see any group size improvement by trimming 0.003” off the front of a neck.

Added later:
Just looked at a SAAMI Chamber blueprint. The prints don’t show the location of the rifling. Another way to determine the distance from the case neck end to the rifling is to determine the bullet touch to the rifling. With a bullet seated to touch in the case. The distance from the touch on the ogive to the end of the case neck is the clearance of the neck end to the rifling. On my 6BR with 60 gr bullets it looks like about 0.100” or more before the case neck could touch the rifling or the end of the forcing cone. I think my logic is OK?

 

[Straightshooter1]

Don't know why guys are obsessed with trim length. If you look at a chamber blue print there is about 0.040” space in front of a cartridge neck. The chambers are cut long for the neck so any factory loaded ammo will chamber. There should be no interference unless you have a hard carbon ring. I don’t worry about it for my varmint rifles unless it’s at least 5 thou over. I don’t think I could see any group size improvement by trimming 0.003” off the front of a neck.

I look at it this way . . .

As I fire my rifle the carbon ring build up in front of the case mouth. If I have variations in neck length, I will have some cases that contact that carbon ring differently than others resulting in some difference in pressure followed by subsequent variations in velocity. The more the carbon ring builds up, the more this can happen. If I keep my trim length uniform, that carbon ring build up won't come into play; at least, not unless the build up is excessive.

So, I feel it depends a lot on how many rounds one is firing between cleanings. I don't see that .003 - .005" of variation in neck length makes much of enough difference in bullet release, especially if one isn't shooting for really tiny group sizes.

 

[jds holler]

I have finally started gauging my "actual" chamber length, with a home made gauge of my own concoction. Most chambers are indeed much longer than listed "trim length". I put this data in the die box, and trim accordingly. jd

 

[big5ifty]

Don't know why guys are obsessed with trim length.

Because I don't want case necks pinched between the bullet and the rifling.

 

[butchlambert]

For my PPC and BR brass I have fireform barrels. I use a stiff load of Bullseye with a Playdough or wax plug. After that it takes very little to expand the brass. Fireforming this way makes the brass grow in length. I trim and then turn the necks.

 

[Dusty Stevens]

Always FL size new brass