Powder for fireforming

[Paddyd]

Is there a prefered burn speed for use in fireforming new cases? Fast, med, slow?

 

[L.Sherm]

Is there a prefered burn speed for use in fireforming new cases? Fast, med, slow?

I've fireformed alot of different cases for different AI cartridges, always with the same powder i intend to use after forming, they will shoot quite well if you work up a load just like any other cartridge.

 

[wkdickinson]

I just use a reduced load and kind of look at it as a way to use up odd lots of powder I have no other use for.

 

[Sniper338]

Unless you have a second fireform barrel cut with the same reamer to fireform on a different barrel... just load em and shoot to fireform. Standard load, get the full psi bang on the brass.

 

[Mark M.]

I agree with sherm, I've experienced the same results as described above, This subject I believe has a lot of variables and areas that should be approached with caution, one of the things I’ve done in the past fireforming 17 Ackley hornet, ( the case capacity is about 13 grains) is use 6 grains of the faster burning tight group powder with a little ball of tissue in the end instead of a bullet, fireformed about 95%+ of my annealed case, then, go into load development from there, worked very well

 

[RegionRat]

Many times, a wildcat rig shoots pretty good while fire forming brass.

Allen Thomas would shoot in club matches and kick your butt while fire forming his 6 Dasher brass back in the days before you could buy factory Dasher.

So, I treat it like any other shooting and don't look back.

 

[Mark W]

I just use my intended bullets and powder and work up until a find an accurate load that gives me nicely formed brass.

 

[M-61]

Many times, a wildcat rig shoots pretty good while fire forming brass.

Mine sure do.

 

[Paddyd]

I think we're talking about two different things here. When I say fireforming, Im not talking about making Ackley cases, or wildcats. Just fireforming new cases to my chamber. I probably should add to the variables that during the first firing, I load long about .010" into the lands to keep the case heads tight on the bolt so as not to be stretching the body near the web, something I mistakenly left out of my original question and why I am asking whether I should be using a slow or fast powder.

 

[RegionRat]

No, there isn't a real reason to change the type of powder for the virgin cycle and then a different one for the rest.

Folks can do what they want, but there isn't an engineering based "need to change" the powder type based on internal ballistics and I have never seen any evidence that a slight change in the pulse shape of the pressure trace resulted in a difference in how the brass formed to a chamber.

Remember that the pressure in a chamber of a bottleneck rifle cartridge is on the order of 50 to 60 KSI.

It can take more than one cycle to fully move the case to a stable state, but that isn't driving someone to switch powders between the first cycle and the rest.

As long as the pressure peak is in the same family, you are going to work that brass. YMMV