Three years ago I started getting worked up about making my .300 Winchester Magnum as accurate as possible. I decided at that time to start fireforming my brass and then neck size only for my hunting loads. I decided that I would find a bullet of like shape and weight for my fireforming load and just have fun practicing with it. I have fireformed quite a number of cases with this method. Now, after researching further, I am wondering if I am getting a good fireform on the brass, or just wasting my time. I have not been seating the bullets to contact the lands, and the more I read and research, it appears that without doing so I may not be getting a proper forming of the brass.

From what I can gather from this and other resources, if the brass does not back up against the bolt face during the firing process the primer will be backed out the distance the brass was away from the bolt face. If this is the case, I wonder if I am o.k. because I am not aware of a time that I have had the primer extruding after the shot.

I am not opposed to loading my bullets to the lands, I am just confused as to whether the efforts I have put in thus far have really been kind of a waste of materials, time and barrel life.

Any help on the subject will be greatly appreciated.

Thanks.

So, in theory I could take fresh brass from the maker, seat a primer in it without the pocket uniforming and flashole deburring, charge the case with x number of grains of powder, seat the bullet on top (after chamfering of course)to a specified distance from the lands and this should shoot accurately enough that I shouldn't see a marked difference between this and...

Fireforming the cases. Uniforming the primer pockets. Deburring the flash holes. Trimming to same length. Chamferring and deburring the case necks. Neck sizing in a lee collet die. Charging with same x grains of powder and seating the bullet to same specified distance from the lands.

I am not trying to stir the pot or be a smart alleck. I am just trying to decide if what I am doing is worth it.

For additional information I am shooting a stock Browning A-Bolt in Stainless Stalker (no boss). The caliber is a .300 Winchester Magnum. Two loads I have worked up with the method with markedly more work are:

1.
Fireformed WW Brass/Neck sized
Federal 215M Primer
74.5 grains of IMR 4831
180 grain Swift Scirocco
Ave. Velocity (chrono'd) 3160 fps
Groups (3 shot) hover around .75 to 1 inch depending on the day and me.

2.
Fireformed WW Brass/Neck sized
Federal 215M primer
80.0 grains of H1000 (Have now determined this to be to hot via loose primer pockets)
200 grain Nosler Accubond
Ave. velocity (chrono'd) 3038 fps
Groups (5 shot) hover around 1 inch

I know one of the answers I will get is that I need to try it both ways. I understand that part, but I would like to see what everyone thinks as it may be several weeks before I can get to the range.

Also, will pressures be enough different with new vs. fireformed brass to worry about?

Winnie,
This is just my opinion , but for hunting loads , I would not go through all the motions. 1 inch is plenty accurate . For me , the extra effort would not be worth it.

You purchase virgin 300 Win Mag brass and it is already to load and fire. Why do you say your firefroming brass that is already made to fit your rifles chamber. That brass is produced to SAMMI specs to fit any standard 300 Win mags chamber. All your doing is making that virgin brass fit your chmaber perfectly when you fire it the first time.

If you were fire forming your brass to fit your chamber you would have a wild cat chamber that virgin brass is not availble to you. You fire form brass to fit a non-standard chamber using a parent case as close to your wild cat case as possible. What your actually doing and your thinking are not in sink.

All you need do to the 300 Win mag is treat it just as you would any unbelted cartridge and neck size it only after that first firing. That moves head space to the shoulder where it should be not on the belt. You are waisting much barrel life and ammo if you think your fire forming your 300 Win Mag brass. All your doing is getting a perfect brass to chamber fit in your particular rifles chamber, not fire forming.

Neck size, maintain consistant case length, chamfer case mouth, deburr flash hole. Now you can develope your most accurate loads for your rifle. Seat your bullet so it just touches the lands to start. Test loads in 1/2 grain increments in three round lots from starting load to maximum load listed. Take the best group of that lot then readjust seating depth .003 into the case in lots of three rounds. If your final group is not to your liking try another powder and start over at the begining. When you finfd the powder, primer, bullet your rifle groups best with, then you must duplicate that accuracy load.

Reloader66,
I'm going to respectfully disagree just a little bit.
Seating hard into the lands works fine if one already knows that headspace is minimal, but that's not always the case with factory rifles chambered for belted mags. Don't underestimate the ability of the firing pin spring to seat the bullet further into the neck, adding to the clearance we were trying to eliminate by jamming into the lands. I like to size only about 1/2 of my necks. Without polishing down an expander or crimping, bullet grip is significantly reduced.

There can easily be over .006" difference in the measurement between the case head and shoulder of new unfired brass, and a fireformed belted case. That represents a lot of stretching at the pressure ring, and case life just went down the tubes. Necking up and back down is a more sure way to completely eliminate headspace, which matters if brass longevity is an issue.

And yes, I do think the term "fireform" is appropriate. We're just playing symantics, but when a brass case if formed to the chamber under fire, I call that fireforming, whether we're dealing with a wildcat or not, and especially when the case shoulder is moved slightly forward because of excessive chamber tolerances. If you ignore the belt and measure for headspace from the case head to shoulder datum on new and fired brass from your own 300 WinMag, you just might see a difference, and I assure you that the difference came at the expense of brass at the pressure ring.

No flames intended. I just see it differently.

I don't know, but it would seem to me that if one were concerned about these issues the best way to correct them would be to have the rifle rebarreled, and use the same set of chambering reamers to both chamber the barrel and make a set of custom dies for that particular rifle. Case closed.

Blue