Fire Forming while building a load?

LeeEnfieldNo.4_mk1

LeeEnfieldNo.4_mk1

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Anyone ever fire form there new brass while building a load? Way I see it is regardless, the brass will expand to final size so any volume discrepancies should pretty much be eliminated. Seems a little odd to waste powder and bullets on a light fire forming load.

Any thoughts?
 
Fire forming with cornmeal theoretically will fill out the shoulders properly by giving some mass to push it evenly against the chamber.
What caliber, rifle or pistol, bottleneck or not?
Using pistol or rifle powder?
 
I shot 143gr ELD-X's out of brand new Hornady cases in my Tikka 6.5CM CTR while doing load development. Out of the eight different charges of H4350, I got 4 one ragged hole groupings. Nobody told me I had to fire form the cases prior to load development. Lol
 
I use new brass all the time when developing loads. How else would you know how much expansion you are getting unless you compare your fired case against new brass.
 
LeeEnfieldNo.4_mk1 said:
was referring to new fresh brass of the same caliber. remember being told you should fireform new brass.
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I had some brand new .243 Winchester cases that were .009 to .012 shorter than my GO gauge. So I loaded the cases with a mid range load and seated the bullets to jam and fire formed them to keep the cases from stretching. The funny part was I fired some extremely tight groups by accident doing this just forming the cases.

The real question here is are you neck sizing or full length resizing. If full length resizing and shooting groups at 100 yards you should not see any difference between new or once fired brass.

From what I have read there is a very slight velocity loss when firing a new case but you would have to be shooting at long range to see any difference in the POI.

That being said at accurateshooter.com I just read a few weeks ago a well known competitive shooter won a match using new unfired Lapua brass.

Bottom line, shoot the new cases as is with your work up load and if needed fine tune the loads after they are once fired.

The big thing with new cases is how much shorter are they are in headspace length compared to the chamber and case stretching.
 
My F-Class rifle is a 260 Ackley.

I form with 4350.

Fire formed brass takes 4831, more than will fit in the virgin 260 case.

So I have two laods. One for virgin cases and one for formed cases.

The 4350 load shoots better.

My next step is to try 4350 in a formed case. It is "too fast" but if it is the most accurate, so be it.


If you are firing brass that is the same caliber as the chamber, I see no reason not to use it for load development.
 
I did a similar thread teo months ago, everybody said I was stupid to try load dev with fresh brass.

I do bushing full length resize only to bump the shoulder and resize 50% of the neck length. probably not even .001 shoulder bump as it required no trim nor did it mesure longer.

My new 6.5CM brass, I loaded 90gr as long as I could with near max published load and 147gr eld match at a load known by the former owner.
 
If you bought a couple different boxes of factory match ammo off the shelf and shot it in your rifle to test accuracy, that would be new brass as well, yet you would still be able to tell what the rifle liked better.

As long as you’re measuring all test loads in the same lot of unfired brass, I think any minor differences vs. fire formed brass would be pretty academic.
 
prevost12 said:
If you bought a couple different boxes of factory match ammo off the shelf and shot it in your rifle to test accuracy, that would be new brass as well, yet you would still be able to tell what the rifle liked better.

As long as you’re measuring all test loads in the same lot of unfired brass, I think any minor differences vs. fire formed brass would be pretty academic.
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I would guess a factory round is not only a new brass as most new brass are smaller than a full lenght sized case.
 
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