Fire forming...

[Sharpsman]

...cases IMO is best performed by loading a bullet overly long in a bolt rifle such that the case head is pushed back against the face of the bolt and using a 90% charge of powder to blow the shoulder forward in the chamber.

[44 AMP]

I wouldn't do it that way.

[Nathan]

Have you done much fireforming?

I find forming even with a good neck/shoulder anneal and a false shoulder and a bullet jammed still results in the case moving forward and stretching at the base. It also can have a high failure rate due to the pressures.

So, I have switched to the COW method with no bullet. I get formed cases with few losses. Also, there is less chance of fire cutting your chamber with this method due to how little powder is used.

[Sharpsman]

I figured you wouldn't!

[Nathan]

How would you do it 44AMP?

[ammo.crafter]

Using 308 brass cut down to a bit over spec, ream inside of case and cut down to spec. run thru Reload dies, measure length and load with 10 less powder, place cork wad over charge, add COW w cork wad to mouth and seal w wax.

[44 AMP]

I don't think jamming a bullet into the lands and then shooting a 90% load is a good idea.

In most cases, I don't bother with fireforming as a separate step, Once I form the case so it chambers, the first load (light, slightly below starting load level) will form it just fine.

[Nathan]

I don't think jamming a bullet into the lands and then shooting a 90% load is a good idea.

In most cases, I don't bother with fireforming as a separate step, Once I form the case so it chambers, the first load (light, slightly below starting load level) will form it just fine.

Let’s say you are making 6PPC from 220 Russian. You would just expand to 6mm and shoot? Won’t you overly stretch the case walls and have quite a few shoulder splits at high pressure?

Honestly, I did it the way you are suggesting. My biggest issues were….neck turn junction was imprecise, primers wouldn’t fire due to poor headspacing. I will use COW method next time.

My turning point was on 300 Sherman. Everything fired, but brass was toast after 4 reloads. Waste of Peterson brass. Did it again with Starline using COW. No stretching. It visibly(with calipers) formed shorter.

I have done 300 Sherman, 28 Sherman Mag, 7-30 Waters by COW so far with no issues.

[Sharpsman]

Frankly I think it's a great idea and I used this procedure in years past to win several 1000 yard matches in the Texas State Matches held over at Fort Wolters Texas. I fire-formed my 300 Win Mag cases using my suggested method to not have to worry with the inconsistent dimensions of the belts from the case heads!

[Nathan]

I fire-formed my 300 Win Mag cases using my suggested method…

I think we are talking about 2 kinds of case forming…

[7.62 man]

I have fire formed brass using wooden bullets with a light load of pistol powder. It worked great. It was back when the 350 legend first came out & I needed brass to reload so I reformed some 5.56 & .223 cases into 350 legend. The LC 5.56 worked best.

[Unclenick]

I agree with Nathan that two kinds of fire forming are being discussed: Major and minor. Major would include feature changes like different shoulder angles and bullet diameters per some of the calibers mentioned. Minor would be forming the 300 Win Mag to headspace on the shoulder instead of the belt or the 303 British to headspace on the shoulder instead of on the rim. In between would be the less dramatic reforming of a case to its Akley Improved version. I think Sharpsman's method is fine for the minor, and the AI cases have long withstood simply firing the commercial parent cartridge loads, so I suspect Sharpman's method with a 10% reduction in powder to allow for the jammed bullet's effect on pressure would likely work for AI as well.

For major reforming, you run into the issue that few cases are formed with perfect brass thickness symmetry, so if you expand them with too much rapidly applied pressure, the lion's share of stretching can occur on the thinner side, exaggerating the difference, work-hardening the thin side and thereby setting up for splits to occur. The COW method works by pushing the COW through like a fluid extrusion die, slower and probably for reasons to do with not applying too much radial pressure initially when the pressure is at the back, does not tend to result in exaggeration of non-uniform thickness, which is its major virtue.

[Nathan]

That is interesting. I never thought about how COW works. Makes sense.

To me, COW is even better than hydraulic forming.

[tangolima]

Fire forming, major fire forming in particular, by definition is to spread given amount of brass over bigger area. It is a weakening process. So I tend to avoid doing it if I have a choice. I did it on rare occasions when absolutely had to. Low pressure, multiple passes is the way.

Minor forming, however, I have done a lot. Never have to do it in as dedicated step though. For instance, pushing out shoulder of .303. The first time I shoot the ammo, it is done. I just don't size the shoulder back. I may consider loading the first load light if it is new brass, instead of loaded ammo.

OP method is ok, except that the round is probably head spaced by the extractor claw instead of the bullet jamming into the riflings. I doubt the bullet hold alone is strong enough to counter the firing strike. If not for the extractor, the round probably will misfire just like handgun round with high primer.

-TL


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[Nathan]

OP method is ok, except that the round is probably head spaced by the extractor claw instead of the bullet jamming into the riflings. I doubt the bullet hold alone is strong enough to counter the firing strike. If not for the extractor, the round probably will misfire just like handgun round with high primer.

That’s the problem….the case walls stretch when you do it that way.