Did an experiment - Why to check and trim brass after FL sizing

[stimpylu32]

I needed to form some more brass for my new Handi 224 GNR and decided to do an experiment at the same time , here is what i found .

Brass started as new 357 max ( Remington brand ) with a trimmed length of 1.594 , i then applied Imperial sizing wax for lube . The brass was formed in a set of custom Hornady FL sizing dies with a Lee turret press . I also set up a mag base with dial indicator to check press flex . ( max flex was 0.003 ) .

Numbers after sizing were as fallows .

Under 1.535 = 11 pcs

1.536 t0 1.540 = 28 pcs

1.541 to 1.545 = 45 pcs

1.546 to 1.550 = 36 pcs

1.551 t0 1.555 = 20 pcs

Over 1.555 = 6 pcs

As you can see there can be as much as 0.020 difference from one case to another , while not all brass will move this much others will move even more . Remember that in some cases brass length will make a big difference in how well a round will group .

Now i'll trim them all to 1.540 and go from there .

stimpy

[Savage]

Interesting that there would be that much variation in brass. Wonder if the brass was from the same lot. Doubtful, at best. I also find it interesting that you only had .003 flex in the turret press. I wonder if the flex in a good "O" frame press would be measurable with a dial indicator? I have both types of presses, but no ready access to a dial indicator. Anyone up to checking that out?
Savage

[stimpylu32]

Savage

The turret press that i used for this is one that i did some mods to , its an older 3 hole that i drilled & tapped to place lock bolts in so as to hold the turret tight almost as a solid press . I use this press just for heavy work like large case sizing and forming .

As for the brass it all came from the same factory 500 count bag , but yes it could have been from diffrent batch runs . Don't have an O press so no help there .

stimpy

[buffermop]

Stimpy. not change the subject, but I am currently loading 357 mag for my revolver. The problem I am having is a buldge accruing  in the center of the case after it goes through the seating die. Could this be caused by not enough opening of the case in the decapping die?

[stimpylu32]

Stimpy. not change the subject, but I am currently loading 357 mag for my revolver. The problem I am having is a buldge accruing  in the center of the case after it goes through the seating die. Could this be caused by not enough opening of the case in the decapping die?

When you say buldge is it at were the bottom of the bullet is or below that point ? It could be a case of you not expanding the case mouth enough during the belling process .

Also are you seating and crimping at the same time ? If so you may be putting too much crimp in the case .

stimpy

[buffermop]

The buldge is where the bottom of the bullet lies within the case.

[Tom W.]

I didn't do any test like yours, but I have measured a lot of brass after F/L sizing and found that the best thing for me to do is to F/L size, trim, chamfer and deburr, then give it a good cleaning. That way there are no surprises later.

 Did you know that a piece of brass that hasn't been trimmed can cause a NEF to break open on it's own after the shot? 


Don't ask how I know.

[Savage]

Stimpy,
My turret has a bit more flex than yours I'm sure! Never checked it, and it hasn't been a problem in my applications. I would guess that as long as the flex is consistent, it should not be of great concern to anyone not loading for bench rest.
buffermop,
As Stimy said, you may need to seat and crimp as separate operations. I use the Lee FCD for crimping. I believe it will solve your problem.
Savage

[skb2706]

Stimpy. not change the subject, but I am currently loading 357 mag for my revolver. The problem I am having is a buldge accruing  in the center of the case after it goes through the seating die. Could this be caused by not enough opening of the case in the decapping die?

If you want to eliminate the bulge don't full length size the case. Only size it down to where the bullet fits in it. In a break action gun there is no reason to size beyond that point in straight wall cases anyway.