Trim before or after neck sizing?


January 24, 2013, 09:43 PM
Just what the topic says. Should I trim before or after neck sizing 30-06 brass?

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Steel Horse Rider
January 24, 2013, 09:48 PM
Trim after sizing. The length may change during any sizing operations since you are moving metal.

January 24, 2013, 10:01 PM
Yup... trim after.

January 24, 2013, 10:03 PM
Alrighty then, just didn't know if neck sizing only made a difference. Thanks guys!

January 24, 2013, 11:02 PM
Another vote for after. They told ya right.

January 25, 2013, 08:00 AM
Should make any difference in length but well probably fit your pilot better if it is size first.

January 25, 2013, 09:20 AM
Generally speaking trimming after sizing is recommended like the above posts have said. I trim before sizing however for the following reasons:

After the neck has been resized, the trimmer pilot fit may be very snug inside the neck of the brass(like kingmt said). It may depend on your particular die and bushing sizes, if you use a die that has an interchangeable bushing setup. Sometimes the trimmer pilot leaves scores,cuts and grind marks inside the neck. I'm not really comfortable with what this does to bullet run-out and accuracy.

Secondly, trimming puts some pressure on the neck of the case in many setups and might cause some misalignment of the neck which is why I'd rather run the case through the resizing die after trimming. .

Granted this may be strictly paranoia and I haven't done serious testing to prove whether or not it makes any difference in accuracy, but my rational thinking says it could. Also I'm talking about ammo I'm making for long range competition shooting. For average use I'm sure it's not worth worrying about. Since you mention neck sizing I'm assuming your concerned about high-level accuracy. (Whether or not neck sizing is the right way to go is a debate for a whole other thread)

All I do is adjust my trimmer to it gives the correct length after resizing. Trim, resize, measure the case and adjust trimmer as necessary. It might take a few pieces of brass to get everything adjusted properly but once it's set up and locked down it works fine.

January 25, 2013, 09:58 AM
“Alrighty then, just didn't know if neck sizing only made a difference. Thanks guys!”

They do not know the effect neck sizing has on case length, it has been suggested “There is a way”, but that involves moving away from the key board etc..

It is believed sizing the neck makes the neck thicker and or thinner, that does not happen, when necking a case neck up the case gets shorter, when necking a case down it gets longer. There is a way to determine fact or fiction, truth from nonsense, problem, work is involved, then there is that part about measuring before and again after.

My most accurate trimmer is the trim/form die, then the other part, I have some old equipment, before I decide to trim before or after sizing I check the pilot by measuring, if the pilot measures .300 for a 30/06 type case I trim before, if the pilot is less than .300 I trim after, a reloader can not look like they know what they are doing while fighting/struggling getting the case neck on/off the pilot.

I have the Dillon electronic case trimmer, when it comes to purchasing size/trim dies I prefer purchasing forming dies, that leaves me with trimming only 223 with the Dillon.

F. Guffey

Pistol Ranch
January 26, 2013, 02:57 PM
Note what fguffey says..When you neck DOWN, the brass gets longer..
Please explain why full size resizing does not, in fact,make your brass longer??
If it gets longer you should trim after resizing to keep your cartridge length uniform and within O.A.L. tolerance..

January 26, 2013, 03:32 PM
Trim after resizing.

January 26, 2013, 04:16 PM
Your trimmer pilot is sized to fit sized case necks.

The cutter may wobble in unsized cases because the pilot will be a loose fit.


January 26, 2013, 04:26 PM
how thick or hard you brass is will dictate if it will strech {get longer} a super short mag will not move when you neck size only as it is thick, a 35rem will strech as it is thiner , your 30-06 is some where in the midle , try it both ways and see, but alway check OAL befor loading , I myself always trims after neck or FL sizeing

January 27, 2013, 05:35 AM
Your trimmer pilot is sized to fit sized case necks.

The cutter may wobble in unsized cases because the pilot will be a loose fit.

Usually but not always. With my redding neck sizing die (which utilizes bushings) the trimmer pilot is such a tight fit that I feel as if it could be misaligning the neck as I trim. That's why I trim before. The end result is the same as long as your trimmer is set up to give the proper case length after resizing.

However this probably only confuses the issue. For most people using a standard die with an expander ball (which is what I assume the OP is using) just trim after resizing.

Friendly, Don't Fire!
January 27, 2013, 07:45 AM
I trim after resizing.

If my pilot is ever too tight, I just put the small end of the pilot into the end of a piece of pipe that is just a bit larger.

Then, I use my bench grinder wheel to take a bit off the diameter of the pilot by holding the pilot/tube end up on an angle so it's not perpendicular to the grinding wheel. This allows the pilot to spin-freely in the end of the metal tube I am using to hold the pilot. The reason you want the pilot to spin while taking a bit of metal off is so you are taking metal off evenly all around. I don't have access to a lathe or other sophisticated-type tooling equipment.

After I have taken a bit off, I try it. If it works, I then just re-blue the pilot where there is now new steel showing.

If it is still tight, I can usually see just where it needs a bit more steel removed, grind a bit more until it is a snug-fit but not too tight, then re-blue.

The pilot for my 500 Magnum was too large, the pilot would spin while locked in the Forster Case Trimmer. That is, until I did as detailed above.

41 Mag
January 27, 2013, 07:45 AM
When I process my cases I usually do the following,
1) tumble until clean and shiny
2) inspect for any defects or other issues
3) pull a random number and measure for length, (*see below)
4) clean all necks and primer pockets
5) lube and size them all and return to tumbler to remove excess lube
6) again pull a random amount and check length (*)
7) set up trimmer and trim and chamfer as needed

(*) In most cases the brass is usually within the trim lenght specified in most manuals. That said, the listed length may or may not be too long for the particular rifle it is going into. Since I have several rifles in some calibers I usually just try to keep everything in the middle of the recommended specs, but for a dedicated caliber I use what the longest lenght is for that rifle.

I trim after sizing as usually if there is any chance the cases will stretch it is when the expander ball is pulled out during the down stroke. I have found this happening with some brands of brass, or calibers, and not with others, but in most cases I am processing a large batch of sometimes mixed cases so when I DO trim they are all the same length when done.

January 27, 2013, 12:05 PM
"It is believed sizing the neck makes the neck thicker and or thinner, that does not happen"

Then Fguffey said there is a way to determine fact or fiction and or truth or nonsense, then he implied most reloaders were too lazy or not curious enough to determine what does happen.

I have suggested most Internet reloaders have not been trained to keep up with more than one thought at a time, as in case stretch, Hatcher, a most quoted expert, moved the chamber shoulder forward .080 thousandths knowing the case head would separate when the trigger is pulled, 'it' did not happen, Hatcher became a fire former, the difference between Internet reloaders and Hatcher, he did not spend the rest of his life claiming excessive chamber length WILL result in case head separation, Case head separation as in insipient case head separation is caused by bad habits.

Hatcher did not have a clue, he fire formed modified 30/06 Hatcher .080" cases and did not get credit for his accomplishment. Hatcher could have formed 30/06 Hatcher modified +.080" cases and fired his modified cases in his modified chamber, his modified cases would have off set the length of his modified chamber,meaning he would have fired cases in his long chamber that were shorter from .001" to .005" than the chamber from the bolt face to the shoulder of the chamber.

Back to the lazy and those with no curiosity. Hatchers cases did not stretch in a manner described by Internet reloaders, Hatcher's shoulders on his cases die not move forward, Hatchers shoulder did not move, the shoulder on Hatchers fired case did not move, the shoulder on his fire formed cases was erased when fired, during firing a new shoulder was formed, one more time the case did not stretch between the case head and case body.

Then there is that part where no one measures before and again after, had Hatcher measured the length of his unfired cases and compared the length with his fired cases he would have found his cases shortened, back to being able to keep with more than one thought at a time" Hatchers cases got longer from the head of the case and shoulder/datum, the rest of the case from the shoulder/datum forward got shorter.

I do not live in the little bitsy world of reloading, I form cases before firing, some of the cases shorten in length .035", some of those shorten an additional .010" when fired.

Not possible for a reloader to comprehend the effect sizing has on a fired case if they do not understand the effect firing has on it.

F. Guffey

January 27, 2013, 12:13 PM
This last post then makes a lot of sense. After posting my original question I went to go trim my fired brass. None of them needed trimming, in fact they were shorter than the max trim lenghth. This means the brass probably filled the chamber area and from that stretching shortened the length of the case. Had I full length sized the brass, that stretching would've been compressed again and made the OAL long again. I think I'm getting this reloading thing down! :)

January 27, 2013, 12:27 PM
Once your case is fireformed, you'll see it *slowly* grow each firing. It depends a lot on your particular dimensions, caliber, pressures attained, etc.

My once-fired neck sized 300 Win Mag will "grow", slowly, shot to shot. Since I neck turn, I can visibly see the un-turned area previously part of the shoulder area slowly edge it's way forward, shot after shot. :)

Shooting in a loose chamber / loose headspaced rifle, will cause brass to grow long, and relatively fast by comparison. The 8x57 brass I shoot in semi-autos grows rapidly. When full length sizing you're not really making the neck LONGER, per se, but shoving the shoulder (and everything behind it) back in to shape. The neck length is controlled by brass flowing under pressure.

Straight walled brass shows the opposite effect, my pistol brass shrinks, OAL wise, from shot to shot. It's subtle and slow, and nothing to grow alarmed about. You'll shoot the primer pockets out of pistol brass before you shrink them to the point of uselessness. :)

January 27, 2013, 12:30 PM
"I trim after sizing as usually if there is any chance the cases will stretch it is when the expander ball is pulled out during the down stroke. I have found this happening with some brands of brass"

Not the first time this claim has been maid, and I said there is a technique/method that would allow a reloader to test their claim, back to expanding the neck, Expanding the neck shortens the neck, sizing the neck down lengthens the neck.

Then there are those that do not understand the effect firing a case 5 times has on the case as in resistance to sizing, and lube, there are reloaders that believe the squeak sound made when the sizer plug is pulled through the neck is normal.

Working with others involved with reloading, there is no way to say "I would not it that way because....", Or "If I was doing that I would do it differently because etc., .......". I have the RCBS Prep center, there is no excuse for having a sizer plug being pulled through the neck with one squeak, two squeaks or three. I have seen reloaders use more force pulling the sizer plug through the neck than they used to size the case, and remember, there are reloaders that have have applied enough force when lowering the ram they pulled the case out of the case holder, then that brings up, and takes us back to the case getting longer, upsetting the case head with the shell holder will lengthen the case by turning the case head edge over.

Again, some of the problems are caused by bad habits.

F. Guffey

January 27, 2013, 12:48 PM
Again, some of the problems are caused by bad habits.

Isn't it that way with most things?

If you're doing it right, simple case sizing operations should be effortless. Even on badly stretched 8mm shot in a loose spec semi auto, with a buldged out back end, that I have to small base size, there's no "struggle" involved.

Applying the proper amounts of lube (e.g. not much at all), and to the right places, and making sure everything is running smooth (e.g. properly spec'd expanding die diameter w/ a smooth engagement surface), clean dies, everything should run smooth.

If it takes any effort to resize your casings, especially on the upstroke, find out why, don't just muscle through the thing.

The only resizing operation I do that involves any amount of effort whatsoever, is 50 BMG. :)

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