Is it necessary to resize new unfired brass? I'm new to reloading and have only reloaded used brass so this may sound like a dumb question. Also, reloading 300 win mag, do I need to use magnum primers? The load manual doesn't specify which primers.

does the brass measure to spec? in not it need to be resized. Are the mouth perfectly round if not you need to resize or at least neck size. What manual are you using, I have yet to see one that did not specify primer. I would imagine that most if not all the powders in the burn range used for the 300 WM in that large a charge weight would greatly benefit from a magnum primer

Thanks Cory, after reading your post I went back and looked at the manual and I was overlooking the primer recommendation in the cartridge specs. Thanks for pointing that out. I haven't measured the cases yet just got them. I'll open and inspect them tomorrow.

I always full length size new brass. Bulk bags always have out of round/ dinged necks.

yes, but I have reloaded brass from nosler, norma, and lapua that did not need resizing, I have also reloaded brass from norma, lapua, Winchester, Remington, starline, and frontier that was in desperate need of resizing.

+1. I don't care who the brass manufacturer is. If it's on my bench it's going to be full length sized for the first firing.

I always size, chamfer/debur and debur flash holes on the orimer pockets.

I once was anal-retentive about deburring flash holes, as well as neck-turning new brass. I no longer bother with this on hunting loads for sporter rifles. The results are simply not worth the time and effort. I will admit that bench and LR guns probably will benefit from these steps, but that's another game altogether.

However, I DO run new brass through a FL sizer that is adjusted for my rifle's chamber.

Almost everyone recommends Mag primers in the .300 Winnie. Not being one to buck the system, I do too.

I also always resize new brass.

Walter

New brass oughta be ready to load, but it often is not due to dinged case mouths---just as others are saying. I suppose you could just run the expander ball down into the neck, but I've always figured if I'm gonna go that far I might as well just resize all the way, but in a die as finely adjusted for my rifle as possible.

I really don't think a .300 Win Mag calls for a magnum primer based on it's size alone, but when you're using those "hard-to-ignite" powders and especially in cold weather it's probably not a bad idea. On the other hand you can use magnum primers in any cartridge you want and it won't hurt a thing. Use em if you got em, and choose em if you like em. You won't be handicapping yourself at all.

I do the primer flash hole debur out of habit after having a batch or two of brass that was horrible. Now all brass get the same treatment.

I full length size EVERY time, including new brass. I also measure ten pieces and set the trimmer to the longest I can get, and still get a square mouth, and I always debur the Flash hole. I've seen lots of pieces of brass with case mouths badly dented, so they need attention anyway.

The 300 Win Mag needs Magnum primers, like CCI 250.

Never ever do I touch new brass anymore. Did it all at first with new brass,
the whole nine yards. Then one time I was in a hurry and did nothing. Guess what.
The groups were exactly the same as when I did all that work. So now I still do the
Work, but I wait until the second loading.

I do not reload any magnums, not sure if that would impact anything. Oh and I use 308 or 223 Winchester brass.

A couple of years ago I bought some new 243 brass from Cabelas. It was either Rem or Win. I loaded without resizing. The bullets were loose in the neck.

I now resize every time.

Yep! always, on new brass.

I have a checklist that I use with every reloading cycle. I resize new brass and used brass just to be safe.

I FL size everything.

Well, I opened the new brass and inspected each case and it's just like the majority of you guys said, dented case mouths, burrs, etc. the lengths were pretty matched but if I have to run the expander ball I might as well finish the stroke and FL resize. Thanks for all the help, you guys are great.

When Full Length resizing be careful as to not push the shoulder back.

I like to smoke the neck and shoulder and run it up into the die and stop a little short from the shoulder.

I disagree. A 3 thousandth bump of the shoulder ensures reliability chambering and ejecting. It also doesn't cause the load to lose any velocity.

I agree while I do just neck size some of the calibers I reload all hunting rounds get fl sized. The last thing I want is to have a round not reliably chamber while im in the field.

Full length sizing is ok. Just be careful not to push the shoulder back that would increase head space.

I should have added that calibers that I mainly neck size is regulated to that single fire arm of which they were fired from.


Each chamber is a law unto itself.

I, like someone suggested, used to always deburr flash holes. Recently, I had a conversation with the man who ran Winchesters accuracy department before he retired and he told me that deburring flash holes was a complete waste of time and effort.

I was happy to hear that since that is one job I hate the most.
Phil

+2

Hmm. I wonder why it is very rare for mass produced ammunition to shoot more consistently than perfectly tuned hand-loads. He's full of chit!