300 Win Mag reloading question

[Clem Bronkoski]

Ok guys I just acquired a 300 Win Mag in a Bergara B-14 HMR. Now I know initially I will have to full length size all my brass but what about after I fire it in my rifle?
Should I partially size my brass (back out the FL sizing die a bit), neck size only or FL resize for longer case life.
Inquiring minds want to know.

 

[Ckleeves]

Shoot your virgin brass, neck size for your second firing and then measure with a comparator after that second firing once the brass is fully fire formed to the chamber and FL size with .002 of bump from then on just like a non-belted cartridge.

I don't bother shooting all 50 or 100 pieces with that process, just take one or two pieces, fire them twice to make sure they are fully formed and then measure, set my FL die for the bump I want (or use a comp shell holder to make things real easy) and use that for the life of the brass.

 

[Ol' Red]

What @Ckleeves said pretty much covers it.

 

[asd9055]

I think by tomorrow you will have many different opinions/advices. Back when I was starting out, I had ONE rifle, One Cartridge. Folloing the advice of my mentor at the time, after the first firing, I only neck sized untill and only IF the rounds would not chamber. Then I would full size. It owrked good enough for my needs then. Now I full size everytime.

 

[memtb]

Ok guys I just acquired a 300 Win Mag in a Bergara B-14 HMR. Now I know initially I will have to full length size all my brass but what about after I fire it in my rifle?
Should I partially size my brass (back out the FL sizing die a bit), neck size only or FL resize for longer case life.
Inquiring minds want to know.

I only have your basic 2 die sets….nothing special!

I also use a belted case similar to the 300 WM. With mine I definitely "do not" contact the die to the ram… once the press has "cam'd" I back the die back a bit, and bring the press ram fully to the top.

Then try the case in the chamber. If you backed the die off far enough….the case should not be chambered. You continue this practice, lowering the die a bit (I go 1/4 turn), bring the ram up…..test the case for chambering.


I repeat this process until the rifle bolt will close with minimal resistance. I say "minimal" as this pretty much guarantees that there will be no case lengthening when firing.

I easily get 10 firings on my AI brass. Loads are at maximum (seeming safe) pressures….I'm pretty pleased with my case life! memtb

 

[Clem Bronkoski]

So you're only resizing a portion of the neck and not really neck sizing. A neck sizing die will only size the case neck. Doing what you're doing is still working the body.
There are two schools of thought on this. One is for neck sizing and the other for shoulder bumping.
I guess I'll try both and see what works for me.

 

[memtb]

Clem, if that was for me. You may be correct. But, I can see how far down the neck the die contacts - reduces the neck OD. I also know, that if I only go down a little way on the neck as indicated by the lube mark on the neck…..the case is difficult, if not impossible, to insert into the rifle chamber and close the bolt!


The search mentioned…..should I search here on the forum, or do an internet search!

Maybe I'm doing it all wrong….but, I think that I'm extending my case life! memtb

 

[wilehunting]

I had a Browning A-bolt 1 once that the chamber was somewhat oversized at the shoulder. I only neck sized the fired case to have the best case to chamber fit with a neck size only die. 300 win mag.

 

[MagnumManiac]

Do not run belted cases into a FL sizing before being fired. Period.
If you want to change interference fit in the neck, get a Neck only die. More advanced measures is what I do, but you won't have the same tools.
Neck size only until the bolt is hard to close, then measure the brass and set your FL die to size .0015-.002". If you don't wait until the brass is hard to chamber, you WILL get erroneous readings and end up bumping too much and wind up with case head separations.
Belted cases NEED to be allowed to settle by firing them in the chamber a few times, it is necessary.

Cheers.

 

[Tiny Tim]

Agree with Magnum. Even if all you have is a FL die, don't run it down completely. Let the brass fully form to your chamber until it gets stiff to close then adjust shoulder bump to your liking, just like any other non-belted case.

 

[FEENIX]

Ok guys I just acquired a 300 Win Mag in a Bergara B-14 HMR. Now I know initially I will have to full length size all my brass but what about after I fire it in my rifle?
Should I partially size my brass (back out the FL sizing die a bit), neck size only or FL resize for longer case life.
Inquiring minds want to know.

 

[CogburnR]

The expound on the do not fully full length size the case.... A lot of belted magnum dies will move the shoulder back a lot, like .020". If you resize the case like that after a few firings it will cause case separations due to the brass lengthening above the belt more than anywhere else. Since the brass doesn't move back into that area it thins out and the case becomes weak and separates. You may find that an Innovative body die is helpful to resize the area above the belt. So, as above... measure your fired brass and then move the shoulder back .002-.003". You can measure that with a 40S&W Case and a caliper or get a case length gauge. If the brass gets difficult to chamber many times the issue is the area above the belt that regular dies don't resize well, a Larry Willis Innovative Body die will resize that area.

 

[ranch manager]

Ok guys I just acquired a 300 Win Mag in a Bergara B-14 HMR. Now I know initially I will have to full length size all my brass but what about after I fire it in my rifle?
Should I partially size my brass (back out the FL sizing die a bit), neck size only or FL resize for longer case life.
Inquiring minds want to know.

Exactly what magnum maniac says. Just fyi as for my 30-338 Winchester my rcbs die is set where it does not move the shoulder. I can chamber a fired case still with a piece of scotch tape on the head. I'm going to continue shooting the brass in until it tells me that I need to make an adjustment

 

[Mike D Texas]

Read what magnum maniac said. Belted mag cases are notoriously short and will stretch a lot on the first few firings. As stated, fire enough time to fully form to your chamber and you notice resistance to closing the bolt. Then full length resize using .002-.003" of shoulder bump.