fire formed cases

[wild thing]

I read about how people fire form their cases then just seat their bullets by thumb preasure. When I fire my 45-70 I can not even start the bullet without expanding the case. Am I missing something?Actually I seem to get better accuracy by full length sizieing and expanding. Please explain. thanks john

[montana_charlie]

To answer your question with any degree of usefulness, a series of measurements (of your stuff) is required.
To start, what is the (1.) diameter of a bullet when it is ready to seat in the case?

If you have been full-length sizing and expanding, you are seating the bullet into some amount of neck tension.
A measurement of the (2.) mouth ID (after sizing and expansion) would be required to know how much neck tension you have.

It is unlikely that your (3.) mouth ID after firing is as small as your mouth ID after sizing and expansion. Measurements should confirm that.
If fired ID is larger than 'sized ID', then belling the case mouth should allow you to seat a bullet without further manipulation of the case dimensions. Whether that can be done without a press is dependant upon the numbers from the measurements above.

CM

[oldracer]

A question like that is why it took me over 6 months to finally settle on what would shoot the best in my gun(s)! Fortunately for me when I bought my 2nd and 3rd 45-70s I had a pretty close starting point so it did not take as long. Some things I tried were full length sizing or fire forming or fire forming with slightly belled cases. Next was to crimp or not crimp. Next was bullet diameter, should it be .457 or .458 or .459 or even .460 and do I size them and so on. I finally settled on .459 and had to open out the Lee sizer slightly and I do run the bullets through to make sure they are concentric. They are a light finger pressure fir in the case to where they touch the milk carton wad.

I would suggest trying all the possibilities and recording what you do and shoot at least 20 rounds of each setting. I would also say to only change one thing at a time.

[wild thing]

Thanks guys. Right now I do not have any fired cases to measure, I have sized them all. As soon as I can get out and shoot I will measure the fired mouth. Right now I have A .4595 measurement at the base of the bullet and the sized and the expanded neck size is .4575 for .002 neck tension. The way I am loading right now , with full length sizeing and expaanding I am getting groups of 1 1/4 to 1 1/2 at 100 yards. thanks for responding. This board is always full of helpful ideas. john

[Don McDowell]

Am I missing something?Actually I seem to get better accuracy by full length sizieing and expanding.

If you're getting better accuracy full lenght sizing and expanding, then why are you worried about doing it any other way?

Are you missing something? only the boat if you keep fooling around trying to make something work for you that you already say doesn't work for you.

[powderburnerr]

sounds like you are overcrimping a weak charge of powder with a big boolit and the case isnt expanding enough to blow out the crimp.

[littlejack]

+1 on what powderburner said.
What is the powder and weight used? Are you roll crimping the boolit in place?
Jack

[wild thing]

The bullet is the 457125 from Lyman over a charge of 63.5 gr of Swiss i1/2. no crimp. john

[John Boy]

The bullet is the 457125 from Lyman over a charge of 63.5 gr of Swiss i1/2. no crimp Put 70grs of powder in the case and come back from the range - Happy

[littlejack]

Yes sir, your powder charge is too light. Dot NOT roll crimp the boolit. Adjust the crimp die to just take out the flare in the case.
I burn 70 grains (weighed) of GOEX 2F with that same boolit in my Uberti Hiwall.
Jack