Are there any fire-forming experts here experienced with fire-forming cases which are shorter than the chamber?

I have read suggestions such as "Just shoot them - they'll fill the chamber". Perhaps so, but not after just one shot. Seems like it would take at least one more, if not two.

There was also a suggestion to overload with a slow burningpowder, allowing the bullet to set firmly on the powder with the bullet being firmly seated in the lands. Perhaps, but sounds a little dangerous to me.

Would there be a chance of too much pressure buildup if I did the following which would not allow the firing pin to move the case forward prior to ignition?:

Neck size a trimmed .270 case down to .25 just up to the point the unsized portion would not allow the overlength case to move any further forward than is needed to close
the action. Then seat the bullet just enough to kiss the rifling. This would allow very little forward motion when struck with the firing pin and should fill the chamber
after the first shot. But would there be too much pressure during this process?

Anything but an expert, but this is how I fireformed 19-223 from 223 brass. Sized the neck down to 19 but left a secondary shoulder to force the brass against the bolt. I've been told you can't be sure that jamming a bullet will force the case against the bolt. I fireformed using the "cream of wheat" method and it works just fine.

" Sized the neck down to 19 but left a secondary shoulder to force the brass against the bolt."

Thanks, Stan,

When you speak of a secondary shoulder, is
that what I was unknowingly talking about
doing in my question? Did you leave just
enough of the neck unsized so as to keep
the case shoulder away from the chamber
shoulder until the powder charge went off?

Hmmm....19/223? The Calhoun round? Right
now, I'm having trouble with an overlength
25/06 chamber in my T/C Encore. That may be
ok, though, cuz I'll need to do a similar
operation to another barrel that should be
here in a couple of weeks, the Tactical 20.
As it is also based on the .223, we will
have very similar cartridges!

I guess it depends on how close the formed case is to the chamber. I neck-up 5.56 to make 7TCU. Fire-forming straightens the case body a little and blows the neck angle out to 40 degress (without checking, I think that's correct). I load formed brass the same as fire-formed. I can't detect enough difference in performance to try anything different.

Eddie

In fire forming 303 Epps from std 303British, I just fired normal factory or normal reloaded 303 cases, about 1% failure rate (split neck).