.300 / 7mm WSM neckingdown ?'s

[WARDOG]

Good day fellow shooters. I have been reloading for over 20 years but mostly for hunting applications and a few target applications. My most recent project is necking down .300 WSM brass to make 7mm WSM using Norma brass. I have never necked down, or "wildcatted" a cartridge so I have a few questions.
I am using a Redding Competition Die set: Seater Die, Body Die, and Neck die.
The.300 WSM case has a neck thickness of .0155"
According to my reamer dimensions, I would like to get a 7mm WSM neck thickness of .015". The reamer is for a standard WSM Match chamber, No tight neck etc.
Using the Redding Competition Bushing Die, I have bushings of .311, .312, .313.
Obviously necking down increases the neck wall thickness. Getting the O.D. necked down to .313 will leave the I.D. of the neck too small for the pilot of the neck turning tool, or to seat a bullet.
My dies do not have an expander ball to properly form the I.D. of the case. Do I need to buy a separate die with an expander ball to get that initial .2825 I.D.?
Is there a better way that I am not getting?

Also- I plan on fireforming 300 pieces of brass (Not sorted or culled yet). I have an unshot, Krieger barrel on a Surgeon action. I realize the life expectancy of the throat will be around 1200. I hate to use up 25% of the barrel life fireforming brass.
Has anyone else used a "Mule Rifle" (A inexpensive, or worn out rifle in 7mm WSM) to fireform brass to get it close enough to my chamber specs to start serious reloading?
I can't find a tired 7mm WSM chambered rifle yet so I am looking at purchasing a Savage or other inexpensive brand in that cartridge just to do the brass forming operations.
Any thoughts on that?
Thanks-

 

[bear458]

Re: .300 / 7mm WSM neckingdown ?'s

You PMed me, I'll respond here.
I use a seperate expander with inserts die to open up the neck for a slip fit on the neck turner mandrel, then use the appropreate bushing to give .002 tension.

On the fire forming, My suggestion is to load the bullets long enough to push the case head against the bolt face. This will keep the cases from streching.
I shot my new unformed brass at matches and couldnt tell any difference in the target indications between that brass and fireformed brass.
They both shot well. I wouldn't waste the powder and bullets,, much less the barrel life, on fire forming.
The cartredge has done well for me at the target range and would be awesome in a hunting application.

 

[Bacarrat]

Re: .300 / 7mm WSM neckingdown ?'s

Why not just do it the easy way and use Winchester 7WSM brass?

No fire forming
Last a really long time
Gives good accuracy with little prep


Unless you are having a 7-300WSM built, I just don't see the need to necking up and down 300 or .270 WSM cases when the standard 7WSM cases work fine.

 

[bear458]

Re: .300 / 7mm WSM neckingdown ?'s

using .300WSM cases results in a little longer neck,, and I'm not a fan of Winchester brass in this application, just a preference

 

[Bacarrat]

Re: .300 / 7mm WSM neckingdown ?'s

What's wrong with Winchester brass? I got 15+ loadings out of my cases and the SD's were around 6 or 7 with very little case prep. Hard to argue with that.

 

[WARDOG]

Re: .300 / 7mm WSM neckingdown ?'s

<span style="font-weight: bold">Thanks for responding Bear458-</span>I am experimenting today with necking down and I am having some difficulty.
The .313 bushing is <span style="font-style: italic">definitely</span> too small, giving poor neck quality and varying thicknesses. Since I can't get a consistent neck thickness I can't get the math done to figure out the correct bushing size.
<span style="font-style: italic">Papagrizzly</span> gave me some necked-down cases last fall, sized & neck turned, Sized, once fired & neck turned. I am using those as examples of what I should be getting. Wall thickness on final neck size, once fired is .0145" which jives well with my reamer dimensions, BUT....I am not getting even close prior to neck turning.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bear458</div><div class="ubbcode-body">I use a seperate expander with inserts die to open up the neck for a slip fit on the neck turner mandrel, then use the appropreate bushing to give .002 tension.</div></div>
Could you provide the "expander and insert die" you are referring too?
What case neck lube could you suggest?
If you also did the same thing I am trying to so with the .300/7mm WSM what was the bushing die you ended up using to size the neck prior to neck turning?
Did you anneal prior to necking down?

<span style="font-weight: bold">Bacarrat-</span> I tried using Win brass but I had to cull too many because they were all over the place in variance. I realized after culling 35% of my Win brass, I should bite the bullet and get the Norma brass. I really won't know the long-term or accuracy benefits of the two makes of brass until I do some shooting.

 

[Bacarrat]

Re: .300 / 7mm WSM neckingdown ?'s

I don't weight any of my cases and still get pretty decent SD on my loads. Or what I think is good SD's.

How much better do you want to get on the SD? But if you want to waste time and weigh each case, measure every bullet ogive, measure each powder charge to the kernal, be my guest. About the only thing I do on case prep is to chamfer and debur my cases, neck size with only .001 tension, and no neck turning,

 

[bear458]

Re: .300 / 7mm WSM neckingdown ?'s

I've had that tool for a while, Sinclair sells an updated one (pt # 05-3000)they use a floating mandrel # E-28. I think Imperial die lube is your best bet for this operation, apply to the inside of the neck,(leave it there to prelube for the neck turn op)Turn enough off the neck to end up with .003-.004 clearence between the loaded round and the ID of the chamber neck. Measure by miking a case with the bullet inserted in the neck
It's been a while since I prepped those cases, I'll try to figure out which bushing I used (I may have turned them after expanding)when i get home after work.
I did not anneal these cases, if you do, do it after you neck turn, (brass work hardens during machining)
The reamer and fired cases u got from papagrizz are <span style="font-style: italic">very</span> similar to mine (hint).
I don't remember too much trouble downsizing the case necks, I may have done it in 2 steps. The smaller the step downs the more evenly they seem to behave.

I just re-read your orignal post, since you have a no turn neck on your chamber, just take enough off to give a minimum of .003 to .004 clearence (if you can get it that tight) if not , no big deal

 

[dragonjr45]

Re: .300 / 7mm WSM neckingdown ?'s

Great info from bear there. I necked down 300 wsm to 7mm a while back.

I neck turned all of my norma 300 wsm brass before necking down to 7mm. Not sure if that was the way to go, since part of what got turned ended up in the shoulder area. In fact next time, I will mostly likely turn after necking down. I haven't had any problems so far though. Now, IF I remember correctly, I turned the neck walls down to .013" and after necking down it had grown to about .014".

If you can I would neck down in 3 or 4 steps. I like to try not to neck down more than .005 at a time. I've heard necking down more than .007 at a time could cause runout problems.

As bears said, you really do want .003 to .004 clearance. I ended up starting around .0025 and was have flyers.... a lot of flyers. I turned my cases down a bit more to give .004" clearance, and the flyers are gone.

Also, its probably not the best idea to use a bushing die in conjunction with neck turning. best bet it to use a full length non bushing die. A bushing die will leave a small part of the neck unsized and when you run your neck turner over that area it will leave it a little thinner than the rest of the neck. Probably won't cause problems or anything, but just sayin it would be ideal to use a non-bushing die

 

[bohem]

Re: .300 / 7mm WSM neckingdown ?'s

The base to shoulder length on 7 WSM is longer by about 0.040" than the 300 and 270 WSM. If you properly form 7 WSM to true 7 WSM dimensions from 300 WSM brass you don't get a longer neck. The shoulder moves and takes up that neck length.

You can make 7 WSM brass from either of them, but it's going to require you to create a false shoulder in the neck and fireform just like you would do with an AI version of the 223 or 30-06.

The Cream of Wheat method is a good way to minimize barrel wear from fireforming, just clean out the bore well before firing any actual bullets through it.

I have a 7mm/300 WSM that shares the base to shoulder height on the 300 WSM, it's just necked down brass is all. Ballistically speaking, they are twins and I chose it for easy brass availability, longer neck length, and the fact that I already owned a 300 WSM so I only needed to buy a 7 WSM neck sizing die and trim the bottom back about 0.050" for forming brass. I didn't need a whole new set of dies.