300 Win Mag brass

SJB358

Ballistician
Dec 24, 2006
31,355
656
thanks Scotty , that's what I thought .


Fellas , this false shoulder trick works on any bottle neck cartridge , not just belted cases . if you have a generous chamber , that leads to short brass life from case head separation, this sure would be worth a try .
for sure Jim. I started it because a 22-250 Lapua case was pretty lose in my chamber and I didn’t wanna stretch it. Worked like a champ. I’ve got a 9.3 that has enough slop with new Hornady brass that unless I do it the first time it has enough space to make it misfire.

Guys, this is a great discussion. I had also found that the shoulder reference point (head space) on new belted brass was up to .017" short. I had remembered reading about making a false shoulder, but I couldn't remember how. I will be starting to load 300 WM this spring and I was hoping I would run across it somewhere. This discussion is very timely for me. Since I have to order an expander just for this is, there a better size then the 8mm to use. Weren't there some cartridges that ran .311 or .312 size bullets? Maybe that is not enough to create the false shoulder.

Dan

Dan, you might be fine going small than .321 but it won’t hurt anything either.
 

TackDriver284

Handloader
Feb 13, 2016
1,801
481
Scotty, which one of these would be a better choice? I have the die for the expander mandrels. There is a .322" mandrel.

Or the taper sizing buttons in 8mm?
 

jimbires

Handloader
Aug 16, 2011
2,496
459
Dan , you want to go bigger than, .311 - .312 . these are only .003 - .004 bigger in diameter than the .308 bullet . the chamber should have at least .004" clearance at the neck , to allow neck expansion for bullet release when fired . expanding the case with a .311 - .312 would probably fit in the chamber , defeating the false shoulder .

everything I've read about false shoulders states to neck up to next caliber size . by going up about .020" for the false shoulder you will have enough brass against the chamber to hold the case tightly against the bolt face .

put a nice chamfer on the brass case mouth , and use lube to neck up the brass . go slow you don't want to collapse the case shoulder .
 

jimbires

Handloader
Aug 16, 2011
2,496
459
for sure Jim. I started it because a 22-250 Lapua case was pretty lose in my chamber and I didn’t wanna stretch it. Worked like a champ. I’ve got a 9.3 that has enough slop with new Hornady brass that unless I do it the first time it has enough space to make it misfire.



Dan, you might be fine going small than .321 but it won’t hurt anything either.



after that first fire , as long as you properly size the brass case , that loose chamber doesn't hurt a thing . it's all about sizing the brass to your chamber .
 

jimbires

Handloader
Aug 16, 2011
2,496
459
here's a question ; where do you draw the line . how far do you allow the brass to stretch on the first fire , before making a false shoulder ?
 

ShadeTree

Handloader
Mar 6, 2017
2,761
1,177
Scotty has this nailed from what I've read down through. 1 caliber size up will generally do it unless they are running too close. For example a 243 you would need to skip 257 and go up to 264, or at least I would. On 257 you would skip 264 and go up to 277. You want enough of a step up wall on the bump that it doesn't get squeezed down and back any when the firing pin tries to drive the case forward. I've done it a bunch on a 22-250 and a 250 savage, and some on a 257 Roberts Ackley.

On a bolt gun I like to remove the firing pin and spring so the bolt flops freely up and down with no resistance. That way as I'm adjusting the die down creating the false shoulder and checking by chambering, I can feel exactly when it's adjusted down to where it gets just solidly snug against on the last final movement of closing of the bolt. I want it snug against that false shoulder but not tight.

Once I have my die set where I want it, I usually chamber the next 2 to be sure it's sitting against that shoulder how I want it, then run the rest through.
 

ShadeTree

Handloader
Mar 6, 2017
2,761
1,177
here's a question ; where do you draw the line . how far do you allow the brass to stretch on the first fire , before making a false shoulder ?
Not sure you can get a correct answer on that Jim. It would be a matter of opinion and there's not really a wrong answer. For me I'd probably put up with as much as .006 or so. If it was any sloppier than that you are taking a lot of life out of the brass on the very first firing. But again, if somebody else doesn't mind that, it's not a wrong answer.

Also I'd quicker put up with some slop on a particular chamber on the first firing if I have plenty of brass for it, or can easily and cheaply enough get it. Hard to get brass, or brass I've paid a lot of money for, I'd qucker go through the bother of a false shoulder even if it wasn't real bad by any standards.
 

Bruce Mc

Handloader
Oct 26, 2005
1,033
76
Great discussion, thank y'all. I have several hundred unfired hornady and norma 220 swift cases to prep, I'm gonna give it a try. Should easy to fit the case to a #1 single shot.
 

SJB358

Ballistician
Dec 24, 2006
31,355
656
Scotty, which one of these would be a better choice? I have the die for the expander mandrels. There is a .322" mandrel.

Or the taper sizing buttons in 8mm?

I use the Sinclair expander mandrels. Either would work I’d think. I like the mandrels though. They make a set .002 under bullet diameter.
 

SJB358

Ballistician
Dec 24, 2006
31,355
656
here's a question ; where do you draw the line . how far do you allow the brass to stretch on the first fire , before making a false shoulder ?
Jim, I’m cheap and scratch deep for Lapua, ADG, etc. If it’s more than a few thousands I’ll make the false shoulder. Only takes a tiny bit more time to save brass from the get go.
 

DrMike

Ballistician
Nov 8, 2006
35,203
1,762
I use the Sinclair expander mandrels. Either would work I’d think. I like the mandrels though. They make a set .002 under bullet diameter.
I purchased a full complement of the Sinclair expander mandrels years ago. I use they religiously on new brass. They have proven to be an investment that was invaluable.
 

ShadeTree

Handloader
Mar 6, 2017
2,761
1,177
I purchased a full complement of the Sinclair expander mandrels years ago. I use they religiously on new brass. They have proven to be an investment that was invaluable.
Just to throw out another option, for necking up one could also choose the Hornady expanders. They are shaped very much like a bullet, so as long as there is some lube on the inside of the neck they are much easier than trying to do it with the short and fat expanders that are on a lot of dies like RCBS.

They thread right onto your standard decapping rod that is on a RCBS die. Run a couple bucks cheaper a piece than the Sinclair's and you don't have to purchase a separate die. I like them a lot, but I've never had or used the Sinclair so I'm not claiming they are just as good or better, but they do make life go easier for that purpose.
 

jimbires

Handloader
Aug 16, 2011
2,496
459
Not sure you can get a correct answer on that Jim. It would be a matter of opinion and there's not really a wrong answer. For me I'd probably put up with as much as .006 or so. If it was any sloppier than that you are taking a lot of life out of the brass on the very first firing. But again, if somebody else doesn't mind that, it's not a wrong answer.

Also I'd quicker put up with some slop on a particular chamber on the first firing if I have plenty of brass for it, or can easily and cheaply enough get it. Hard to get brass, or brass I've paid a lot of money for, I'd qucker go through the bother of a false shoulder even if it wasn't real bad by any standards.


the brass I have a pic of above is short by about .005 - .006 when new unfired . I size my brass with about a .002 shoulder bump . so you can get good life from that starting point .

you are right ,Scotty is a smart reloader .
 

jimbires

Handloader
Aug 16, 2011
2,496
459
I've bought a few sets of mandrels from 21 century , and have a few from sinclair. the dies and mandrels are interchangeable . I like the 21 century die better , it has a window so you can watch the brass and stop before you bottom out .
 

SJB358

Ballistician
Dec 24, 2006
31,355
656
I purchased a full complement of the Sinclair expander mandrels years ago. I use they religiously on new brass. They have proven to be an investment that was invaluable.
Hence the reason I have mine! I’m pretty sure you whispered that tidbit once upon a time.
 

SJB358

Ballistician
Dec 24, 2006
31,355
656
I've bought a few sets of mandrels from 21 century , and have a few from sinclair. the dies and mandrels are interchangeable . I like the 21 century die better , it has a window so you can watch the brass and stop before you bottom out .
I’ve heard the 21st Century stuff was great as well.
 

DrMike

Ballistician
Nov 8, 2006
35,203
1,762
That twenty first century stuff looks very good, though I've never actually used any of it. The expander mandrels look akin to those from Sinclair. No doubt it is good stuff.
 
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