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Sizing 300win mag?

smokinbobf4

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Dec 26, 2018
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So I am fairly new to reloading, about a year in, and was wondering if there are any tips to reloading for a belted magnum? I have read a bit on it and some say do just the same as any other. Some say you have to use a collet die, which I’m not even 100% sure what that does or how it works. I have a full length Redding type s sizing die for it. Any tips would be greatly appreciated!
 
Suggest you just use basic RL procedures and see if you have any issues. Normally none will show up. Belts get a lot of attention, some positive, some negative. It's best just to ignore the belt and drive on.
 
That’s what I was going to do, just thought I would check as some people seem to get pretty set on doing certain thing to prevent head case separation.
 
Just bought one of these ... waiting for it to arrive. Curious to see if it helps extend the life of my 300-WM cases.

 
Just bought one of these ... waiting for it to arrive. Curious to see if it helps extend the life of my 300-WM cases.

I bought one and it works very well. I saved some old cases that I had on the shelf. I'll get a few more round out them
 
Treat like any other....push the shoulder back .0015-.002 and call it a day :D
That’s what I was going to do, just thought I would check as some people seem to get pretty set on doing certain thing to prevent head case separation.
Thats it, minimal shoulder bump, if .001/.0015 works that's where you stop. Bolt runs easily you're good.
 
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Start with virgin brass shot in your chamber only, and stick with it... Stay away from pick-up brass shot in someone else's chamber (which I nickname "toilette" brass) :).... If you do, you'll experience fewer problems, and, you may not have to buy the Larry Willis collet die....
 
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Just bought one of these ... waiting for it to arrive. Curious to see if it helps extend the life of my 300-WM cases.

This^^ Have a couple of 300WM and use this die after annealing and prior to FL sizing. Fire form the brass and set the shoulders back .001 to .0015 using comparators. The Wheeler method is also a good way to setup dies if you don't mind removing the ejector. New factory brass is all over the place since it is designed to headspace off the belt. Norma brass in my rifles lengthen anywhere from .013 to .017 after fire forming. Dedicate brass to a particular rifle. The book Precision Shooting Reloading Guide by Dave Brennen had an excellent chapter on reloading the Winnie.
 
You can ignore the belt, until you can't. .001-.004 shoulder bump, make sure you are setting up your FL die with brass that has fully expanded to the chamber. With normal brass this sometimes takes two or three firings in the the 300wm, because of the amount the shoulder has to move forward before you can heapsapce off it instead of the belt. Peterson makes 300wm long brass that is much closer to actual chamber dimensions of the 300wm unlike other commercial brass.
 
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All good info, thank you everyone. I have a few boxes of factory Barnes ammo that I was going to break the barrel in with and then use the brass from that.
 
This^^ Have a couple of 300WM and use this die after annealing and prior to FL sizing. Fire form the brass and set the shoulders back .001 to .0015 using comparators. The Wheeler method is also a good way to setup dies if you don't mind removing the ejector. New factory brass is all over the place since it is designed to headspace off the belt. Norma brass in my rifles lengthen anywhere from .013 to .017 after fire forming. Dedicate brass to a particular rifle. The book Precision Shooting Reloading Guide by Dave Brennen had an excellent chapter on reloading the Winnie.
Just making sure ... instructions (and video) are clear that the collet die goes "after" the full-length sizing die. Do you do it the other way around? Seems like you'd want the shoulder and body sizing first (pushing and bulging) ... and then check above the belt and size with the collet die if necessary.
 
You can ignore the belt, until you can't. .001-.004 shoulder bump, make sure you are setting up your FL die with brass that has fully expanded to the chamber. With normal brass this sometimes takes two or three firings in the the 300wm, because of the amount the shoulder has to move forward before you can heapsapce off it instead of the belt. Peterson makes 300wm long brass that is much closer to actual chamber dimensions of the 300wm unlike other commercial brass.
+1.

Play around with sizing staying off the shoulder until you find your real head to shoulder headspace measurement.
 
Just making sure ... instructions (and video) are clear that the collet die goes "after" the full-length sizing die. Do you do it the other way around? Seems like you'd want the shoulder and body sizing first (pushing and bulging) ... and then check above the belt and size with the collet die if necessary.

^^^^This^^^^ The instructions are clear, use the Willis die after F/L sizing. You also use the top of the die as a Go / No go gauge. After regular F/L sizing, you drop the case in the top of the Willis die to see if it drops in to the belt. If it stops before the belt, you need to size that case in the Willis collet die.

I've been using one for years.
 
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^^^^This^^^^ The instructions are clear, use the Willis die after F/L sizing. You also use the top of the die as a Go / No go gauge. After regular F/L sizing, you drop the case in the top of the Willis die to see if it drops in to the belt. If it stops before the belt, you need to size that case in the Willis collet die.

I've been using one for years.
Got it ... that's what I thought. Just curious ... how many firings are you getting from your 300-WM cases?
 
The go/no go on the die is quite a bit smaller than what will fit in both of the 300wm barrels I have owned. If you don't load hot you may never need the LW die. Loading conservatively I had to do some brass at 10, loading hot I had to do it again after 3.
 
I just started for reloading 300 win and my plan is to just neck size till the shoulder stops growing. Once that happens, I’ll bump shoulders like everyone else is saying. If the case starts to bulge near the belt, I’ll get one of those Larry Willis dies to smooth it back out and keep going
 
^^^^This^^^^ The instructions are clear, use the Willis die after F/L sizing. You also use the top of the die as a Go / No go gauge. After regular F/L sizing, you drop the case in the top of the Willis die to see if it drops in to the belt. If it stops before the belt, you need to size that case in the Willis collet die.

I've been using one for years.
FYI Initially used the LW die after sizing as listed in the instructions. Measurements before and after indicated the headspace increased approximately .001. Since I am only minimally setting back the shoulder I found it better to FL after using the collet die. Personally this works best for me.
 
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FYI Initially used the LW die after sizing as listed in the instructions. Measurements before and after indicated the headspace increased approximately .001. Since I am only minimally setting back the shoulder I found it better to FL after using the collet die. Personally this works best for me.
Your explanation makes sense for you.

The only reason I posted this is because your method is the opposite of what the manufacturer of the die recommends. It was posted for others who haven't used the die and are contemplating buying it.
 
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Got it ... that's what I thought. Just curious ... how many firings are you getting from your 300-WM cases?
I haven't been losing much brass. The rifles I reload for are hunting rifles, not target rifles. It takes me a long time to cycle through my brass.
 
FYI Initially used the LW die after sizing as listed in the instructions. Measurements before and after indicated the headspace increased approximately .001. Since I am only minimally setting back the shoulder I found it better to FL after using the collet die. Personally this works best for me.
Same.