Trying to understand fire forming

[rmkey]

Why use cow or corn meal or bullets into the lands? I am starting with new Lapua 260 brass. The cow method does not force cartridge head against bolt face. The bullet method wastes bullets,primers and powder and barrel for nothing. My question is why not just load using your pet load in the first place? You then can compare with the next load to see improvement in accuracy. I take it that the only reason to fire form standard calibers is to move the shoulder forward, measure and adjust die to set the shoulder back say 0.002 for subsequent firings. I speak only of standard calibers not forming AI or converting to another caliber.

 

[watercam]

If you are not modifying the case there is no reason not to simply load and shoot. I shoot new brass in High Power Long Range competition with no ill effects. Benchrest could be an issue I suppose but someone with that experience will no doubt chime in.

 

[MagnumManiac]

There is no need to to fireform standard cases for mechanical reasons...but for load work up, a case should be as close to chamber spec as possible.
I do not use cases in my comp guns until they have had 3 full power loads while developing seating depth tests and powder/pressure testing. They only get neck sized after this.
The reason for the fireforming and neck sizing only for 3 shots is so that the brass is stable. Even 2 pieces of brass after 2 firings may expand differently, causing different internal capacity. 3 firings generally irons out any difference in all but the very hardest brass.
For my hunting guns, I use NEW cases for hunting with.
Once fireformed I relegate to powder/pressure testing of new powders or bullets.

Hope this helps.

Cheers.

 

[TC260]

The cow method does not force cartridge head against bolt face

Not with a bullet but there's another case forming technique called a false shoulder that does.

 

[rardoin]

If you are not modifying the case there is no reason not to simply load and shoot. I shoot new brass in High Power Long Range competition with no ill effects. Benchrest could be an issue I suppose but someone with that experience will no doubt chime in.

^^^^^^ What watercam said ^^^^^

Just load and shoot. You might require a little powder charge adjustment after a firing depending on the length of your chamber compared to your brass base to shoulder length. I shoot F-open and some of my best 600 and 1000yd scores have been with new brass. Even when I was shooting a 6.5 x55 AI I was able to shoot cleans at 600yds fire forming new brass; it gained almost 4gr in capacity in the first firing.

 

[carlsbad]

2 things you need to accomplish to fire form:

1. Create enough pressure to form the brass to the chamber.
2. Hold the fireform round back against the bolt so the firing pin hits the primer.

--jerry

 

[JSH]

Why use cow or corn meal or bullets into the lands? I am starting with new Lapua 260 brass. The cow method does not force cartridge head against bolt face. The bullet method wastes bullets,primers and powder and barrel for nothing. My question is why not just load using your pet load in the first place? You then can compare with the next load to see improvement in accuracy. I take it that the only reason to fire form standard calibers is to move the shoulder forward, measure and adjust die to set the shoulder back say 0.002 for subsequent firings. I speak only of standard calibers not forming AI or converting to another caliber.

There are a lot of things left out for the question.
What platform
Intended purpose hunting, pleasure, etc.



I see people buy a bone stock off the shelf rig, then buy Lapua brass and think they are set to start hitting stuff at 1k right off the start.

Don’t set to much into fireforming unless the rig deserves it. I have played with enough wildcats to know fireforming loads can be very accurate. The same goes for off the rack rifles with handloads.

Unless there is some kind of issue with chamber or gun,a large majority of shooters won’t see a bit of difference in their group using fire formed brass.

 

[carlsbad]

Like JSH said. Most won't see the difference. Ive seen matches won while fireforming dasher. OTOH, I find my 284 win groups tighten up after one firing. --Jerry

 

[rmkey]

Platform Savage lrp. I plan to get a custom chamber for Lapua brass and Berger 130 Otm tactical combo. I do not hunt, I target shoot against an ornery competitor being myself. Pleasure maybe but my goal is at least consistent 0.5 moa minimum.

 

[rmkey]

Thanks to all -these are very helpful replies. Just last night I had the pleasure of talking with an accomplished competitor. He basically said load and fire your pet load and then look for improvement after a couple firings. He just won a thousand yard match with a 260 holding .45moa to target. Lot of skill there even with a perfect gun/cartridge.
Maybe I will rebarrel in 260 since the gun came with a target action

 

[JSH]

Platform Savage lrp. I plan to get a custom chamber for Lapua brass and Berger 130 Otm tactical combo. I do not hunt, I target shoot against an ornery competitor being myself. Pleasure maybe but my goal is at least consistent 0.5 moa minimum.

You answered what may well be one issue. More often than not we are our own worst enemy.

I have found if I go to the range with basically a F it mood, just going to have fun today it is what it is, I can shoot some ridiculous groups.
Let something rattle me even on the way there, it will carry over. There is as much mental as there is skill.

 

[edwardware]

In mild forms where the neck-shoulder junction is already close to 0 space, I simply lube the cases and shoot a mid-level parent-case load. The same smear of Imperial as for sizing works.

I do the same for pricey-brass (.375H&H, etc) brass for the first firing. It completely eliminates case stretching and primer extrusion, and blows the shoulders fully forward instead.

 

[XTR]

From personal experience I can tell you that more than one F class match has been won with virgin brass. It all depends on your discipline and what you are trying to achieve.

The last time I shot virgin brass in a match was 2018 mid range national championships at Raton. I had the highest X count in F-TR. Go figure.