need some sizing help

[TOPGuN050]

hows it going? I have a question for all of the reloaders here that may be a stupid question but I am a bit unsure and want to be positive I am doing the correct thing.

I recently picked up some once fired brass from a friend for my 300wm. I have never loaded any once fired from a different gun only brass that started as factory, fired from my rifle and reloaded.

I am finding that when measuring off of the shoulder, the brass I got from him is around .010-.015 shorter than the once fired from my rifle. I was told to just full length resize it all for the first round and go from there... the OAL of the brass is very close, within .003. its the length I am getting using the comparator measuring off of the shoulder that is bothering me. I usually bump my shoulders .003 when loading my ammo and the once fired I bought is quite a bit shorter than after doing that to the stuff from my rifle.

my question is, should I still FL resize it all considering how much shorter it is from my other cases? or should I possibly just neck size it this time to fire form and then resume my normal procedure?

if it matters its all black hills match brass (300 pieces) all fired from the same rifle.

any help on this would be greatly appreciated.

 

[P7M13SC]

Run one piece through the sizer and see where it measures on the comparator. Because it is from a different chamber I would full length resize them all the first loading.

 

[flashhole]

Do they chamber in your gun if you neck size only? If yes, just neck size them and load them up. Might want to do a small batch and compare results to FL sized loads.

From your description it sounds like your gun may have a generous chamber. If that is the case FL resizing will result in overworking the brass causing a short brass life.

You should be mindful of case head separation and check the brass for thinning above the top of the case head by dragging a feeler (bent paper clip) along the inside case wall. With a bit of practice you will easily be able to detect differences between a new case and one that is thinning. I use a small BBQ skewer with a slightly bent tip as a feeler.

 

[buffybuster]

With belted magnums the headspace is established by the belt, not the shoulder. That is why the shoulder dimensions are inconsistent. I would as a matter of uniformity FL resize all of them.

 

[Victor N TN]

With belted magnums the headspace is established by the belt, not the shoulder. That is why the shoulder dimensions are inconsistent. I would as a matter of uniformity FL resize all of them.

The headspace MAY be set from the belt. But if it doesn't chamber, it doesn't matter. I have always set the dies for my 300WinMag the same as I set them for every other rifle I have had. If the comparator says -.002 to -.003" and the bolt will close, that's where I put it. Fired in another rifle or not. Size them all the same. Other wise you're overworking the brass for nothing.

(Just be aware that rounds loaded in 95*F in the summer will chamber differently than rounds loaded at 50*F. The season you are going to shoot them in should also be considered. summer loads vs. Winter fired, the bolt may be stiff. This applies to all rifle brass loaded on the -.002" principal.)

The gunsmith that built my 300WM is also a benchrest competitor I have shot with / against for years. I asked about the die to squeeze the belt. He said his brass had gone over a dozen loads without needing the belt squeezed. He told me he had the die to do that. But he hadn't used it in years.

Good luck & be careful.
Victor

 

[DAVETOOLEY]

SAAMI specs for the length of the chamber from the bolt face to the datum line on the shoulder is 2.2791"+.010" So when you figure in the difference between the go gage and the no go gage everything is in spec. I would do two things. 1. try a piece of fired brass in your rifle. 2. size to address any issues you found in step one. One thing to remember is when sizing the body you will force the shoulder slightly forward. It's like squeezing a tube of toothpaste. The body tries to move in both directions. At that point creep down on the FL die until you tap the shoulder and/or you can get the case in and out of the chamber easily since that is the goal.

 

[witchhunter]

Always resize new brass, this includes new to you used brass. Consistency is the key, if your dies are adjusted correctly, you will be ok.

 

[leadbullet]

full length resize all of it then shoot them in your gun then size enough to fit your chamber. pretty simple.
cheers.

 

[FLIGHT762]

I would F/L size the cases with your F/L die set to your shoulder bump. This is what I did with some 7MM Remington Magnum cases. The once fired cases from another rifle were about .010" shorter in shoulder bump than cases fired in my rifle. So far, so good.

 

[TOPGuN050]

thanks everyone for the replies