OK step by step

[Clem Bronkoski]

Ok guys, and I mean the precision shooters, help me out with a step by step. I took a lot of your advice on reloading so far but I still have a couple questions regarding my new 300WM. I bought some Petersen 300WM long brass that is waiting for me at my friends house when I get back to PA.
Now you guys said I should not FL size my new brass but initially I want to insure concentricity of the case mouth. So what I was thinking is to set up my FL sizing die so that the case goes in just far enough for the mandrel to enter the case mouth and the neck portion of the die just starts to reduce the case mouth diameter - maybe 1/16"-1/8". That would be for initial loading.
After fire forming do the same but lower the mandrel/decapping pin far enough down to punch out the primer. Or should I purchase a universal decapping die for this?
Once I'm sure I have the case fully fire formed to my chamber I will FL size just bumping the case shoulder back .0002". I have the comparator to take the measurements.
If I'm missing something let me know. Being on a fixed income I can't be going and buying tons of expensive brass so I want it to last and still be consistently accurate.
Thanks in advance

 

[lancetkenyon]

With the Pererson Long brass, it is pretty close to what your fired will be.

I would just expand the necks with a mandrel to about .003 or .002" neck tension.

Then go shoot.
When you get back, decap the fired brass and measure headspace and see how much they grew compared to virgin.

Realize, .300WM spaces off the belt, not the shoulders. So it might take 1 or 2 firings to fully stretch.

If your brass chambers fine after the first firing, neck size but don't bump your shoulders back. Load them up and fire again.

Decap and Measure again and try to chamber a round. If the bolt has some drag, set your FL die to bump back .002-.003" on the shoulder and lock it down.

 

[Clem Bronkoski]

When you say neck size I believe you mean to just run the case into the die enough to deprime but not touch the shoulder but enough to resize a portion of the case neck. Do this until the case will not chamber or chamber with resistance then measure the case using the comparator and gradually screw in the die, run the case in and keep checking measurement and chamber fit. You only want the case to just chamber with little to no resistance.
Am I thinking right?

 

[lancetkenyon]

When you say neck size I believe you mean to just run the case into the die enough to deprime but not touch the shoulder but enough to resize a portion of the case neck. Do this until the case will not chamber or chamber with resistance then measure the case using the comparator and gradually screw in the die, run the case in and keep checking measurement and chamber fit. You only want the case to just chamber with little to no resistance.
Am I thinking right?

Yes...kind of.
If you are using a FL die to do this, you WILL be sizing the body some, even if you are not bumping the shoulders back yet. That should only be the last .003" of untravel when you are at that point.

 

[M118LR]

You can also purchase dies that just resize the neck, they won't do a full resize. At every reload check for neck cracking if your not annealing, and watch your trim to length. Since the 300 WM has a tendency to stretch beyond standard trim to length in short order. JMHO YMMV.

 

[Bang4theBuck]

When you say neck size I believe you mean to just run the case into the die enough to deprime but not touch the shoulder but enough to resize a portion of the case neck. Do this until the case will not chamber or chamber with resistance then measure the case using the comparator and gradually screw in the die, run the case in and keep checking measurement and chamber fit. You only want the case to just chamber with little to no resistance.
Am I thinking right?

Why not pick up an inexpensive Lee Neck collet die? They are the most cost effective means of sizing necks only.

 

[Shane Lindsey]

You say mandrel, but sounds like you are talking about the resizing button on the decapping stem.

What dies are you using? Does your die have a large and smaller one? If so, use the smaller one, as this will not open the neck up once you size it down, then use the mandrel. If you do not have a mandrel, use the larger button, your neck tension may be a little on the tight side, but that is ok for fireforming.

I use a bushing die that sizes the neck down to my desired neck tension and then use a mandrel (separate die and operation) to uniformly open the inside neck diameter up to my desired tension.
.330 bushing
.305 mandrel
.335 neck tension

 

[Clem Bronkoski]

You can also purchase dies that just resize the neck, they won't do a full resize. At every reload check for neck cracking if your not annealing, and watch your trim to length. Since the 300 WM has a tendency to stretch beyond standard trim to length in short order. JMHO YMMV.

Thanks for all the advice. I realize the 300WM headspaces on the belt and does have a tendency to stretch, I think it because of its short neck. That is the reason I want to be very cautious to size only enough to chamber smoothly. I want my cases to last as long as possible. As for neck sizing, from all I am seeing, none of the champion shooters do that anymore. The only bump back the shoulders using a FL die or a specialty die just enough to chamber the round.

 

[Stadoc]

Why not pick up an inexpensive Lee Neck collet die? They are the most cost effective means of sizing necks only.

^^^this

 

[MOA or bust]

Clem, After your brass has stretched and formed to your chamber (2-3 firings), then you no longer neck size, but just bump .002 or whatever you choose using the FL die. But you need to neck size only for the first few firings to let the body/shoulder stretch out to fit your chamber.

 

[BRADMOTO]

I use Pete Long for 300WM. Easy button is: that longer brass + set your FL sizing die to bump .002-.003 back from fire formed length. Then find other things to complicate your thoughts, but this don't have to be one of them. LOL

Plain vanilla 300WM cases stretch .015-.020 depending on brand. The Pete long brass in my chamber only lets it grow/blow the case .003" longer than virgin state. Pretty daggum cool in my book. I can reload with the same recipes new or subsequent fired brass. Takes out the fireforming step.

 

[Alibiiv]

With the Pererson Long brass, it is pretty close to what your fired will be.

I would just expand the necks with a mandrel to about .003 or .002" neck tension.

Then go shoot.
When you get back, decap the fired brass and measure headspace and see how much they grew compared to virgin.

Realize, .300WM spaces off the belt, not the shoulders. So it might take 1 or 2 firings to fully stretch.

If your brass chambers fine after the first firing, neck size but don't bump your shoulders back. Load them up and fire again.

Decap and Measure again and try to chamber a round. If the bolt has some drag, set your FL die to bump back .002-.003" on the shoulder and lock it down.

I reload for a .300WM. After the first firing I push the shoulder back .002-003 thousandths and headspace off the shoulder. Is there a reason to have to headspace off the belt? I'm just curious about what you have written here about head spacing off the shoulder.

 

[BRADMOTO]

I reload for a .300WM. After the first firing I push the shoulder back .002-003 thousandths and headspace off the shoulder. Is there a reason to have to headspace off the belt? I'm just curious about what you have written here about head spacing off the shoulder.

Only the first firing headspaces off the belt.

 

[M118LR]

I guess there are specialty tools that will allow for proper uniform and concentric tensioning of the Projectile if neck sizing isn't part of the process. I would look into that. JMHO YMMV.