Fire Forming

[J-cat]

It was probably sized with a 7.5 swiss sizer die to open the mouth, then a "fireforming" load was fired in the Swiss which effectively makes the cartridge take the shape of the chamber, which it might not have been able to do perfectly with just a sizer die.

Edit to add:
with my .303 enfield, I bought some PPU brass to load. Since they hadn't been fired in any chamber yet, and since enfields have a LOT of head space, I chose to fireform the cases. I did this by loading a projectile with a pretty mild powder charge. However, since the enfield is rimmed, I slipped an oring around the case so that the rim would be pushed hard against bolt face when chambered. This forced the case to expand forward mostly in the shoulder area and not in the head area of the case. Now, I neck size them only, and they headspace off the shoulder instead of the rim, giving me hopefully 10-15 reloads per case instead of 3 which is typical from .303

If you are really chasing accuracy, you will fireform you brass to your chamber before working up a load. Obviously you need to neck size as well.


The cartridge with the 30 cal bullet wouldn't even chamber in the other firearm with the .284 bore. The bolt wont close. You won't be able to pull the trigger. The problem comes from people shooting things like .311 projectiles down a .308 bore. They will still chamber, but pressure will increase big time, and possibly ka-boom.

No it won't.

[Whiterabbit]

WhiteRabbit
You can point the gun downrange when using Cream of Wheat.
I use 15 grains of Unique then completely fill the case with Cream of Wheat. I then tap on the side of the case with the same spoon I used to fill the case until the COW has settled to the base of the neck.
I then use a 1/4 sheet of toilet tissue tamped in place with a small screwdriver to hold the COW from spilling out.

If your going to a larger diameter neck it is advisable to use a false shoulder. The false shoulder holds the case firmly against the bolts face preventing case stretch in the web.

Cool. Fortunately I prefer controlled round feed guns (actually I don't, I just prefer the claw extractor and I get CRF for free) so I have the luxury of having the bolt face close already.

Unless the slop between the rim and the boltface is close enough in your opinion to result in the same issues?

[JagerDog]

Cream of Wheat (COW) method is your cheapest route. A smidge of fast burning powder and a primer.

Some good tutorials on youtube and blogs.

[ar15barrels]

Unless the slop between the rim and the boltface is close enough in your opinion to result in the same issues?

Don't rely on the extractor for headspace.
Set the case shoulder firm against the chamber sholder and the case head firm against the bolt when fireforming.

[Whiterabbit]

the belt, in my case. As I think back, that's kinda critical information.

[AragornElessar86]

Can someone explain the o-ring situation? Does it go between the case head and the bolt face or in front of the case rim? Is this for setting the case OAL?

[Whiterabbit]

it's for setting the case firm against the bolt so the case does not rattle around while the shoulder is getting pushed into the front of the chamber.

From a practical standpoint, I cannot explain it.

[ar15barrels]

Can someone explain the o-ring situation? Does it go between the case head and the bolt face or in front of the case rim? Is this for setting the case OAL?

O-ring?

Are you talking about a false shoulder?

[J-cat]

I think he's saying he's placing an o-ring between the rim and the rim recess in the chamber. He must have a lot of clearance.

[ar15barrels]

I think he's saying he's placing an o-ring between the rim and the rim recess in the chamber. He must have a lot of clearance.

Who is doing that?

[Whiterabbit]

thenodarb is, in post #2. search in page for oring. I assume thats what aragorn was asking about in post 21. I dont understand it either, thus "can't explain it".

[71MUSTY]

There's a great video from a guy in England on how to use the Cream of Wheat method

Works great but firing the Cream of Wheat Loads always made me hungry.

[waveslayer]

Works great but firing the Cream of Wheat Loads always made me hungry.

It's the fastest and most enjoyable way to heat up your oatmeal

[AragornElessar86]

thenodarb is, in post #2. search in page for oring. I assume thats what aragorn was asking about in post 21. I dont understand it either, thus "can't explain it".

Yeah, I've heard it before and never looked into it. So basically, if you've got a lot of clearance, you put the oring in and it makes sure the head of the cartridge is pushed all the way up against the bolt face, so that your fireformed cases are the exact size of your chamber, shoulder to bolt face. Makes sense, though I'm not sure I totally understand the necessity of it.