OK, probably another stupid question

[balderclev]

When shooting straight walled ammo like 9mm, 40s&w, or 45acp always out of the same pistol, is it necessary to resize them? I would think I could just deprime them, bell, prime and load. What am I missing?

 

[nettlle]

If the diameter of the case mouth is too big after expanding the case may not fit in the chamber.

 

[oldandslow]

bc,

Not a stupid question at all, especially as with rifle cases fired out of the same rifle can just be neck sized and not full length sized.

I would think that one significant problem is that without resizing your case the bullet may not be gripped as tightly and you may have bullet setback in the case when chambering a round thus leading to higher pressures which may be unsafe. You may also have accuracy problems as the setback would not be the same each time. Let's see what others have to say.

best wishes- oldandslow

 

[tightgroup tiger]

9mm is not straight cased.
it's tapered so it has to be full length resized or you will have no neck tension to hold the bullet.
If the cases are truly straight walled and you are shooting low to medium powered loads you may get away with just neck sizing for a semi-auto. They may not chamber very well.

I neck size only my .357mags for my revolvers and they work fine but their not self loading.

As short as .40 and.45acp are full length resizing isn't much more than just neck sizing.

If this one pistol you are using has an unsupported chamber you will have to full length resize anyways to get the bulge at the base of the case or it's guaranteed not to chamber.

 

[Walkalong]

You need to size them.

 

[RandyP]

I can only speak for MY setup, but the 1st die station on my Lee turret sizes/deprimes/primes in one complete stroke. Never considered 'not' sizing.

 

[Magnum Shooter]

With the way dies are made, you might as well size when you deprime. RCBS used to make dies that deprimed and expanded the case mouth, but I don’t believe they still manufacture dies that way.

 

[noylj]

Take a fired case and try to drop it into the chamber. In general, the case is expanded such that it will NOT drop back in the chamber and the bullet will simply drop through the case mouth.

 

[kcofohio]

As oldandslow said, bullet set back. Take an un-resized fired casing and, by hand, push a bullet into the mouth. Jacketed and plated bullets will generally slip right in.

Find the SAAMI specs for the casing of 9mm. Then measure a few fired casings with calipers. I bet you'll find them out of specs.

 

[straight-shooter]

I always deprime using a universal Lee die and then wet tumble them so the primer pockets are cleaned. This is where I could see skipping the sizing process although I don't. If it were me I would and do still resize in the process.

The reason for using the Universal Lee die instead of resizing and depriming in one step before wet tumbling is I don't like to run dirty brass into my die.

 

[rcmodel]

As noted, you have to resize the cases or you will have no (zero) case neck tension to keep the bullets from falling out, or falling in.

Try it.
Set a bullet in a fired case and watch it fall in.

rc

 

[Comrade Mike]

The 9mm is not a straight walled case. It's tapered.

 

[gamestalker]

Even with true straight walled cases, such as .357 or 38 spcl. you would at least need to do a partial resize, other wise it's pretty much guaranteed you'll have no neck tension to speak of, therefore during firing you'll end up with bullets jumping out of the case mouth before they come into battery. This would also cause a locked up cylinder and powder spilled every where.

As for AL cartridges like 9mm, .40 cal, and 45 ACP, it's absolutely necessary to resize, it's the right way and safe approach. I couldn't begin to imagine the degree of unpredictable set back issues alone one would encounter without fully resizing them.

BTW, this was not a stupid question. I'm glad you had the presence of mind to ask first.

GS

 

[Grumulkin]

1. They have to be resized because it you seated a bullet in them it would be too loose.

2. If you had a gun with a very tight chamber, i.e., so tight that a case didn't have to expand past it's point of elasticity when fired, then you wouldn't need to resize. That isn't doable for a semiauto but could be for a bolt action gun; not that I'd really want to.

 

[balderclev]

Thanks to all for the good information.

Jim

 

[Potatohead]

You need to size them.

This^