Wildcat fire forming ?

[upacreek]

I have been toying with the idea of building a 7mm-300. In oder to have say 100 brass does that mean I have to run 100 bullets down the barrel before load development? In my simple mind it appears the only way......or am I missing something?
Please know I do understand the sizing process with dies and trimming. But I am not convinced this will make accurate ammo. Am I wrong?

 

[MudRunner2005]

I have been toying with the idea of building a 7mm-300. In oder to have say 100 brass does that mean I have to run 100 bullets down the barrel before load development? In my simple mind it appears the only way......or am I missing something?
Please know I do understand the sizing process with dies and trimming. But I am not convinced this will make accurate ammo. Am I wrong?

Yes, unless you buy an expensive hydro-forming die from Hornady, and a whole new press, and build a setup that mounts outside so the water doesn't get all in your house, then yes....The only way to form wildcat brass is to shoot them in the chamber of the rifle.

You could always use the cream of wheat method, but I'm not a big fan of shooting breakfast foods and toilet paper down my rifled barrels to have to clean up later.

Just my thoughts.

 

[Brewer]

UPACREEK, I may be misunderstanding your question. When you fire form, there really isn't any way to make more or less accurate ammo. the fire forming process is a way of changing the shape of your brass. no matter how you do it, the only thing that will come out of your chamber after firing is a case is something that looks exactly like the chamber. of course, if you didn't load it hot enough or whatever, it may not be at full shape, but the only place for that brass to go is the chamber.

so once you have your brass formed, then its like reloading any other brass.

so said another way: since you cant buy that brass from the store, you have to make it. The way you make or manufacture it is by taking a case and putting it in the pressure chamber of your rifle and pumping 60,000 PSI into it which forces the brass to assume the shape of the chamber. and there you have it.

I am not familiar with this round, but why do you need to fire form? is there a different angle? if you don't want the angle difference, you can specify the same angle when the smith gets the reamer. the you wont have to fire form.

 

[bigngreen]

A simple 7mm-300 is just a neck sizing and rally, it's just like shooting the 300 brass as new in a 300. If you've changed a shoulder angle or body size then neck size down for a crush fit and pop it of with a fire forming load or load a bullet jambed and fire form.

 

[Lefty7mmstw]

A simple 7mm-300 is just a neck sizing and rally, it's just like shooting the 300 brass as new in a 300. If you've changed a shoulder angle or body size then neck size down for a crush fit and pop it of with a fire forming load or load a bullet jambed and fire form.

+1... you may have a bit of a difference in shoulder dimension but that isn't anything any of use using belted cartridges don't have to deal with already.

Four steps here... size brass in 7x300 die, stuff ammo properly, shoot, repeat as necessary until your barrel wears out or brass fails.

 

[Mikecr]

IMO, all cartridges are wildcats until fireformed in our individual chambers anyway.
You fireform to form your cartridge, and then you load develop with it.
So for 100 formed cases, you fireform 100cases, and THEN you load develop with them.

 

[upacreek]

IMO, all cartridges are wildcats until fireformed in our individual chambers anyway.
You fireform to form your cartridge, and then you load develop with it.
So for 100 formed cases, you fireform 100cases, and THEN you load develop with them.

This is pretty much what i was thinking had to happen. I am new to long range precision shooting. The gun I just had rebarreled doesnt shoot as good as I was hoping and am seriously thinking about another build. If that goes forward 1/2moa is my goal. It just didnt seem right to run 100 bullets through a new gun just to begin load development. But if it needs to be it needs to be.

 

[IdahoCTD]

Both of my 7-300wm's are easily sub 1/2 MOA and are generally between 1/4 and 3/8 MOA. There is very little fireforming that happens. It's about like firing your brass in a 300wm chamber. You can easily do load work up as your firing your brass. I built one not too long ago for a guy that sent me a picture of a 6" group at 1000yds.