Does new brass shoot differently than fire-formed brass?

[Les in Wyoming]

I have hit the holy grail and found an awesome load for my rifle. It has been difficult and turbulent, because my rifle was not consistent. But after glass bedding it and changing how I measure where the bullet meets the lands, I am making a ragged hole with my 300 WM. I am elated. Finally! OK, so I have been reusing brass to do this. I areal and trim etc. Now that I have found my load, I want to load up about 50 rounds to have on hand for hunting before I start experimenting with other bullets, etc. I have 100 new brass cases that are ready.

Here is my question: Will these new, virgin cartridges shoot the same as the fire-formed ones I used to work up my load? I do not want to waste bullets and powder shooting them. Thanks

 

[sedancowboy]

They may not because some pressure is used up fire forming the brass. So for the same charge the velicity will be lower with virgin brass vs fire formed brass. You will have to test and see for yourself. I would caution you about loading ammo up and letting it sit too long because it could cold weld the bullets to your virgin brass.

 

[dok7mm]

Because new brass is formed to fit most all rifles, it could have quite a bit forming in your particular chamber, therefore the combination uses part of the pressure to form the brass to your chamber. It often requires 1 or 2 firings to give consistent velocities when doing load development.

One caution, don't start bumping shoulders back until brass is at max headspace. You can back your FL die out a bit, sizing the neck without bumping.
Then see if the partially sized case will chamber. If it does, it's needs more forming.
If it won't chamber easily, then bump shoulder back a bit at a time, until it chambers easily. If you have a reamer print, it makes it easier to find the proper headspace.

If you've fired brass twice, find a few pieces that show the longest headspace ( usually from the higher velocities). You can then set up your FL die for .002" or so shoulder bump.

 

[Idaholandho]

Because new brass is formed to fit most all rifles, it could have quite a bit forming in your particular chamber, therefore the combination uses part of the pressure to form the brass to your chamber. It often requires 1 or 2 firings to give consistent velocities when doing load development.

One caution, don't start bumping shoulders back until brass is at max headspace. You can back your FL die out a bit, sizing the neck without bumping.
Then see if the partially sized case will chamber. If it does, it's needs more forming.
If it won't chamber easily, then bump shoulder back a bit at a time, until it chambers easily. If you have a reamer print, it makes it easier to find the proper headspace.

If you've fired brass twice, find a few pieces that show the longest headspace ( usually from the higher velocities). You can then set up your FL die for .002" or so shoulder bump.

Excellent advice.

 

[Deputy819]

@ Les In Wyoming

I'll certainly 'second' the great advice mentioned above by 'sedancowboy' and 'dok7mm'.
Last year (October 2020) I worked up a consistent 1/2 minute load in my .300 Win Mag using NEW ADG brass, Berger 210 vld and 74.1gr of RL 26 for a muzzle velocity of @ 2980 fps according to the Magnetospeed. The once fired brass velocity went well over 3,000 fps and required the charge to be reduced to 73.1 gr to stay at/within the same velocity and still print 1/2 minute 5-shot groups. I only loaded up 20 of those for hunting/target work and still have a few left that need to be fired so as to avoid the 'cold weld' possibilities. I have also noted that even the twice fired ADG brass (neck sized only) still chambers just fine with no resistance.

 

[FEENIX]

Here is my question: Will these new, virgin cartridges shoot the same as the fire-formed ones I used to work up my load? I do not want to waste bullets and powder shooting them. Thanks

You have gotten excellent advice about fireforming the new brass until it is stabilized. Regarding your comment about wasting bullets and powder shooting them, it is a matter of personal perspective. For "me", any range of time is not a waste, as I make my trigger time count, and there are always lessons to be learned (most of us keep a logbook of load development for new brass, 1X, 2X, etc.,). I understand the scarcity of reloading components, but it is necessary if your goal is to maximize the potential of your brass/load development. Good luck and happy safe shooting.

 

[swampbug]

All good advice. But also realize that virgin brass may or may not shoot the same or as well as fireformed brass. When I shot benchrest, the consensus was that virgin brass shot the best. Chances are they may shoot different bc the pressure is different but not significantly different. Just shoot a 3 shot group with new and compare to 3 fireformed and see if the new is good enough for your purposes.

 

[slikmrc]

If your die is currently set up for your rifle chamber it shouldn't size your new to much after firing. Awesome you found an accurate load. What bullet did you end up using?

 

[Les in Wyoming]

If your die is currently set up for your rifle chamber it shouldn't size your new to much after firing. Awesome you found an accurate load. What bullet did you end up using?

This is from 208 gr Hornady ELD-M which I cannot get any more of. Noslers and bergers don't shoot in this gun.

 

[GatorTrapper]

If you are shooting big game, you will never see the difference. "Minute of Elk" is the size of a drywall goop bucket lid.

 

[lancetkenyon]

What I would try: load 10 your virgin brass with .1gr and 10 with .2gr more powder than your fired brass load, and go test.
I have found this should put you right about the same velocity, which should be good to go. I have done this with about 20 different 7RM and .300WMs. Worked every time. I don't think that is just coincidence.

Usually, 7RM and .300WM virgin brass is between .014-.021" short on headspace. So they need to form in your chamber like a balloon. Which takes up some pressure to do so. That extra .1-.2gr makes up that lost pressure.

 

[fremont]

One caution, don't start bumping shoulders back until brass is at max headspace.

If you've fired brass twice, find a few pieces that show the longest headspace ( usually from the higher velocities). You can then set up your FL die for .002" or so shoulder bump.

Not to get into semantics, but do you mean "minimum/minimal" headspace, not max/longest? To me, I start bumping shoulders when headspace is gone.

 

[dok7mm]

Well, some times it's better to not get too technical, when trying to answer someone and you don't know how technical he is.

No offense to the OP.

 

[swampbug]

If you are shooting big game, you will never see the difference. "Minute of Elk" is the size of a drywall goop bucket lid.

Shooting elk is like shooting a huge piece of plywood.